Allomelanin-inspired nanoadditives for the radiation protection of polyurethane

Abstract

Aspects of the invention include a nanoadditive comprising a synthetic melanin-inspired nanoparticle, wherein: the synthetic melanin-inspired nanoparticle comprises a plurality of covalently-linked artificial melanin precursors, and each artificial melanin precursor independently comprises an artificial allomelanin precursor, an artificial eumelanin precursor, or a structural isomer thereof. Aspects of the invention include methods of generating polymer nanocomposites and methods of enhancing a mechanical property of a polymeric material.

Description

ALLOMELANIN-INSPIRED NANOADDITIVES FOR THE RADIATION PROTECTION OF POLYURETHANECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 551 ,687, filed on February 9, 2024, which is hereby incorporated by reference in its entirety.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This invention was made with government support under grant number FA9550-18-1 -0142 awarded by the Air Force Office of Scientific Research. The government has certain rights in the invention.BACKGROUND OF THE INVENTION

[0003] Developing materials with radiation resistance against various radiation sources is highly important for the longevity and sustainability of next generation materials. Ionizing radiation can have deleterious effects on materials through the generation of free radicals that can initiate unwanted chain scission or crosslinking reactions that can manifest through measurable changes in material properties.3-5These unwanted side effects necessitate mechanisms to increase the radiation resistance of materials. One method to protect materials from ionizing radiation is to incorporate radiation protective additives directly into polymer matrix to provide protection from within. These additives typically protect the host matrix through absorbing light radiation, transferring or quenching light energy, or scavenging of free radicals generated from radiation.9

[0004] Melanin is a class of biopolymers found in a large variety of living organisms and has been used as an additive for polymer composites. Much of the literature precedent of melanin-based nanocomposites has been dominated by the utilization of synthetic eumelanin materials, namely polydopamine nanomaterials (PDA). There have been previous works towards imbuing PDA into polymer composites.20’21’22 23'24However, PDA is limited by its moderate radical scavenging and requires organic solvents in order to effectively disperse into certain hydrophobic polymer matrices.

[0005] Therefore, there remains a need in the art for radiation protectant additives for polymeric materials.SUMMARY OF THE INVENTION

[0006] Aspects disclosed herein include a nanoadditive comprising a synthetic melanin-inspired nanoparticle, wherein: the synthetic melanin-inspired nanoparticle comprises a plurality of covalently-linked artificial melanin precursors, and each artificial melanin precursor independently comprises an artificial allomelanin precursor, an artificial eumelanin precursor, or a structural isomer thereof.

[0007] Aspects disclosed herein include a polymer nanocomposite comprising: a nanoadditive, wherein the nanoadditive comprises: a synthetic melanin-inspired nanoparticle comprising a plurality of covalently-linked artificial melanin precursors, wherein each artificial melanin precursor independently comprises an artificial allomelanin precursor, an artificial eumelanin precursor, or a structural isomer thereof; and a polymeric material.

[0008] Aspects disclosed herein include a method of generating a polymer nanocomposite, the method comprising: providing a plurality of artificial melanin monomers comprising artificial allomelanin precursors, artificial eumelanin precursors, and / or structural isomers thereof; polymerizing the plurality of artificial melanin monomers to form a synthetic melanin-inspired nanoparticle; and contacting at least a portion of a polymeric material with the synthetic melanin-inspired nanoparticle to generate a polymer nanocomposite; wherein the synthetic melanin-inspired nanoparticle is present in the polymer nanocomposite in an amount of between 0.1 wt.% and 1 wt.% based on the total weight of the polymer nanocomposite; thereby generating a polymer nanocomposite.

[0009] Aspects disclosed herein also include a method of enhancing a mechanical property of a polymeric material, the method comprising: providing a plurality of artificial melanin monomers comprising a substituted or unsubstituted 1 ,8-dihydroxynaphthalene monomer or a structural isomer thereof; polymerizing the plurality of artificial melanin monomers to form a synthetic melanin-inspired nanoparticle; and contacting at least a portion of a polymeric material with the synthetic melanin-inspired nanoparticle to generate a polymer nanocomposite characterized by at least one enhanced mechanical property; wherein the synthetic melanin-inspired nanoparticle is present in the polymer nanocomposite in an amount of between 0.1 wt.% and 1 wt.% based on the total weightof the polymer nanocomposite; thereby enhancing a mechanical property of a polymeric material.

[0010] Without wishing to be bound by any particular theory, there may be discussion herein of beliefs or understandings of underlying principles relating to the devices and methods disclosed herein. It is recognized that regardless of the ultimate correctness of any mechanistic explanation or hypothesis, an embodiment of the invention can nonetheless be operative and useful.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIGs. 1A-1F: Synthesis and characterization of allomelanin-inspired nanomaterials. TEM images of (FIG. 1 A) 1 ,7DHN-NPs; (FIG. 1B) 2,3DHN-NPs. Scale bar = 200nm. FIG. 1C: MALDI-TOF MS Spectra of p-1 ,7DHN and p-2,3DHN. Major peak values are shown in black above the spectrum. FIG. 1D: FTIR spectra of p- 1.7DHN (labeled as (1)), 1 ,7DHN (labeled as (2)), p-2,3DHN (labeled as (3)), and 2.3DHN (labeled as (4)). FIG. 1E: UV-Vis absorption spectra of p-1 ,7DHN (labeled as (1)), p-2,3DHN (labeled as (3)), and p-1 ,8DHN (labeled as (5)). FIG. 1F: DPPH radical scavenging activity of p-1 ,7DHN (triangle), p-2,3DHN (square), and p-1 ,8DHN (circle).

[0012] FIGs. 2A-2F: Fabrication of allomelanin-PU nanocomposites. FIG. 2A: Optical images of p-1 ,7DHN added in various weight percents (0 wt%, 0.1 wt%, 0.25 wt%, and 0.5 wt%) into a commercial Pll resin kit. UV / Vis / NIR transmission spectra (FIG. 2B) and representative stress-strain curves (FIG. 2C) for p-1 ,7DHN-PU composites at 0 wt% (labeled as (1)), 0.1 wt% (labeled as (2)), 0.25 wt% (labeled as (3)), and 0.5 wt% (labeled as (4)). FIG. 2D: Optical images of p-2,3DHN added in various weight percents (0 wt%, 0.25 wt%, 0.5 wt%, and 1 wt%) into a commercial PU resin kit. UV / Vis / NIR transmission spectra (FIG. 2E) and representative stress-strain curves (FIG. 2F) for p-2,3DHN-PU composites at 0 wt% (labeled as (1)), 0.25 wt% (labeled as (2)), 0.5 wt% (labeled as (3)), and 1 wt% (labeled as (4)).

[0013] FIGs. 3A-3G: Tensile mechanical properties of PU Composites pre and post UVB irradiation. Representative stress-strain curves of (FIG. 3A) neat PU, (FIG. 3B) 0.25wt% p-1 ,7DHN-PU, (FIG. 3C) 0.25 wt% p-2,3DHN-PU and (FIG. 3D) Ultimate tensile stress. FIG. 3E: elongation at failure and (FIG. 3F) toughness of composites. FIG. 3G: Young’s modulus pre- and post- UVB radiation.

[0014] FIGs. 4A-4H: Photoinduced changes to surface chemistry of the Pll elastomer composites. Carbon 1s XPS spectra of non-UVB irradiated (FIG. 4A) Pll, (FIG. 4B) 0.25wt% p-1,7DHN-PU and (FIG. 4C) 0.25wt% p-2,3DHN-PU composites. Carbon 1s XPS spectra of UVB-irradiated (FIG. 4D) PU, (FIG. 4E) 0.25wt% p-1 ,7DHN- PU, and (FIG. 4F) 0.25wt% p-2,3DHN-PU composites, (FIG. 4G) full p-FTIR spectra of all composites pre- and post- UVB-irradiation, (FIG. 4H) zoomed-in p-FTIR spectra spectra between 1150-1900cm'1.

[0015] FIGs. 5A-5H: Surface morphological characterization of PU elastomer composites. SEM images of surface of (FIG. 5A) Non-irradiated PU, (FIG. 5B) UVB- irradiated PU, (FIG. 5C) UVB-irradiated 0.25wt% p-1 ,7DHN-PU, (FIG. 5D) UVB- irradiated 0.25wt% p-2,3DHN-PU. Confocal microscopy images of surface (FIG. 5E) Non-irradiated PU, (FIG. 5F) UVB-irradiated PU, (FIG. 5G) UVB-irradiated 0.1wt% p- 1.7DHN-PU, (FIG. 5H) UVB-irradiated 0.25wt% p-2,3DHN-PU. Scale bar (FIGs. 5A-5D) 200 pm, (FIGs. 5E-5H) 50 pm.

[0016] FIGs. 6A-6D: Mechanical Properties Characterization of PDA-PU composites. FIG. 6A: TEM micrograph images of PDA nanoparticles (Scale bar = 500 nm). FIG. 6B: Images of PDA-PU composites at 0.1 , 0.25, and 1 wt%. FIG. 6C: Representative stress strain curves of PDA-PU composites at varying weight percent loadings of PDA. FIG. 6D: UTS, elongation at failure and toughness measurements of the PDA-PU composites.

[0017] FIGs. 7A-7D: Mechanical Properties Characterization of p-1 .8DHN-PU composites. FIG. 7A: TEM micrograph images of p-1 ,8DHN nanoparticles (Scale bar = 500 nm). FIG. 7B: Images of p-1 .8DHN-PU composites at 0.1 , 0.25, and 1 wt%. FIG. 7C: Representative stress strain curves of p-1 .8DHN-PU composites at varying weight percent loadings of p-1 ,8DHN. FIG. 7D: UTS, elongation at failure and toughness measurements of the p-1 .8DHN-PU composites.

[0018] FIGs. 8A-8D: EPR quantification of radical content in p-1 ,7DHN and p- 2.3DHN. FIG. 8A: EPR spectra of 4-hydroxy TEMPO at 5, 10, 100, and 500 pM in water. FIG. 8B: Calibration curve of double integration area vs spin concentration. FIG. 8C: EPR spectra of p-1 ,7DHN at 5 mg / mL in water. FIG. 8D: EPR spectra of p-2,3DHN at 5 mg / m. Radical content of p-1 ,7DHN and p-2,3DHN was determined using the 4-hydroxy TEMPO calibration curve and expressed in units pmol of radical per mg of DHN-nanoparticles.

[0019] FIG. 9: Solvent partitioning of PDA, p-1 ,8DHN, p-1 ,7DHN, and p-2,3DHN nanoparticles into ethyl acetate and water.

[0020] FIGs. 10A-10C: Tensile mechanical properties of the co-polymerized PU and DHN monomer. FIG. 10A: Optical images of (i) 0.25wt% 1 ,7DHN-PU composite (ii) 0.25wt% 2,3DHN-PU composite. FIG. 10B: Representative stress-strain plots of DHN- PU composites. FIG. 10C: UTS, elongation at failure and toughness values of the DHN- PU composites compared to the neat PU.

[0021] FIGs. 11A-11E: Tensile mechanical tests of PU composites at varying wt% (0 wt%, 0.1 wt%, 0.25 wt%, 0.5 wt%) of p-1 ,7DHN. FIG. 11 A: Representative stress-strain curves of p-1 ,7DHN-PU before and after UVB irradiation. FIG. 11 B: Ultimate tensile stress of p-1 ,7DHN-PU before and after UVB irradiation. FIG. 11 C: Elongation at Failure of p-1 ,7DHN-PU before and after UVB irradiation. FIG. 11D: Toughness of p-1 ,7DHN- PU before and after UVB irradiation. FIG. 11 E: Young’s Modulus (MPa) of p-1 ,7DHN- PU before and after UVB irradiation.

[0022] FIGs. 12A-12E: Tensile mechanical tests of PU composites at varying wt% of p-2,3DHN. FIG. 12A: Representative stress-strain curves. FIG. 12B: Ultimate tensile stress. FIG. 12C: Elongation at Failure. FIG. 12D: Toughness. FIG. 12E: Young’s Modulus (MPa).

[0023] FIGs. 13A-13C: Thermogravimetric Analysis of Composites pre- and post- UVB irradiation. TGA graphs pre- and post-UVB irradiation of PU (FIG. 13A); 0.25wt% p-1 ,7DHN-PU (FIG. 13B), and 0.25wt% p-2,3DHN-PU (FIG. 13C).

[0024] FIGs. 14A-14C: Differential Scanning Calorimetry (DSC) analysis of composites pre- and post-UVB irradiation. FIG. 14A: (i) PU control (ii) UVB-irradiated PU. FIG. 14B: (i) 0.25wt% p-1 ,7DHN-PU control (ii) UVB-irradiated 0.25wt% p-1 ,7DHN- PU. FIG. 14C: (i) 0.25wt% p-2,3DHN-PU control (ii) UVB-irradiated 0.25wt% p-2,3DHN- PU.

[0025] FIGs. 15A-15B: Confocal microscopy images of UVB-irradiated composites.FIG. 15A: p-1 ,7DHN-PU at (i) 0.1 wt% (ii) 0.5 wt%. FIG. 15B: p-2,3DHN-PU at (i) 0.5 wt% (ii) 1 wt%.

[0026] FIGs. 16A-16D: Representative stress strain curves of gamma irradiated composites. 0.25 wt% and 0.5 wt% of p-1 ,7DHN-PU and p-2,3DHN-PU were irradiated with 5 kGy (FIG. 16A), 10 kGy (FIG. 16B), 15 kGy (FIG. 16C), and 20 kGy (FIG. 16D) of gamma irradiation and the tensile stress strain curves measuring pre- and post- gamma irradiation are depicted.

[0027] FIGs. 17A-17C: Tensile mechanical properties of gamma irradiated composites. 0.25 wt% and 0.5 wt% of p-1 ,7DHN-PU and p-2,3DHN-PU were irradiated with 5 kGy, 10 kGy, 15 kGy, and 20 kGy of gamma irradiation and their tensile mechanical properties were characterized. FIG. 17A depicts ultimate tensile strength. FIG. 17B depicts elongation at failure. FIG. 17C depicts toughness.

[0028] FIG. 18: General Polyurethane (PU) Synthesis Scheme.STATEMENTS REGARDING CHEMICAL COMPOUNDS AND NOMENCLATURE

[0029] Unless otherwise specified, the following abbreviations are used herein, as will be understood by one of skill in the art: DHN refers to dihydroxynapthalene; PU refers to polyurethane; NP refers to nanoparticle; and Tg or Tgrefers to glass transition temperature.

[0030] The term “amine compound” refers to a compound or molecule having one or more amine groups, where each amine group may be a primary, secondary, or tertiary amine group.

[0031] Wherein the term “alpha carbon” is used to describe an amine compound, the alpha carbon refers to a carbon closest to an N of an amine group. An alpha carbon that is a secondary carbon has one H directly bound to it (e.g., a secondary alpha carbon is bound to an N, two other carbons, and one H). An alpha carbon that is a tertiary carbon has no H directly bound to it (e.g., a tertiary alpha carbon is bound to an N and three other carbons).

[0032] The term “melanin” generally refers to one or more compounds or materials that function as a pigment, such as when internalized or taken up by a biological cell, forexample. It is also noted that melanin is not necessarily taken up by cells. Melanin can be used for forming cell walls in fungi, for example, such as to provide rigidity, defense mechanisms, and more. In another illustrative example, melanin is used by birds, such as where melanin is organized in a matrix of keratin or similar type of biological material, where it can be organized into monolayers or multilayers to provide structural color, warmth, and more. A melanin compound or material may be, but is not limited to, a melanin monomer, a melanin oligomer, a melanin polymer, a melanin nanoparticle, a melanin layer (e.g., a melanin thin film or coating), or other melanin material, for example. For example, melanin nanoparticles internalized by a biological cell function as a pigment in the cell.

[0033] The terms “artificial melanin’’ and “synthetic melanin” are used interchangeably herein and refer to one or more melanin compounds, molecules, or materials, such as melanin monomers, melanin oligomers, or melanin nanoparticles, that are synthesized and are at least partially, or preferably entirely, not derived from or not extracted from a natural source, such as a biological source, a living organism, or a once living organism. The terms “synthetic” and “artificial” are used interchangeably herein when referring to a melanin or a material comprising a melanin. The terms "synthetic melanin nanoparticles" and “artificial melanin nanoparticles” are used interchangeably herein, and are intended to have the same meaning throughout the present disclosure, and refer to nanoparticles formed of artificial melanin, such as artificial melanin monomers and / or artificial melanin oligomers. The terms "synthetic melanin thin film" and “artificial melanin thin film” are used interchangeably herein, and are intended to have the same meaning throughout the present disclosure, and refer to a thin film formed of artificial melanin, such as artificial melanin monomers and / or artificial melanin oligomers. The terms "synthetic melanin layer" and “artificial melanin layer” are used interchangeably herein, and are intended to have the same meaning throughout the present disclosure, and refer to a layer formed of artificial melanin, such as artificial melanin monomers and / or artificial melanin oligomers. An artificial melanin nanoparticle, artificial melanin thin film, artificial melanin layer, and any compound, material, or formulation comprising any of these, comprises artificial melanin monomers, artificial melanin oligomers, and / or artificial melanin polymers. Optionally, an artificial melanin nanoparticle, artificial melanin thin film, artificial melanin layer, and any compound, material, or formulation comprising any of these, consists of or consists essentially of artificial melanin, such as artificial melanin monomers, artificial melaninoligomers, and / or artificial melanin polymers. Optionally, an artificial melanin nanoparticle, artificial melanin thin film, artificial melanin layer, and any compound, material, or formulation comprising any of these, is free (or substantially free) of artificial melanin monomers and comprises artificial melanin oligomers and / or artificial melanin polymers. Optionally, each artificial melanin monomer, artificial melanin oligomer, and artificial melanin polymer of an artificial melanin nanoparticle, artificial melanin thin film, artificial melanin layer, and any compound, material, or formulation comprising any of these, is not bound to, conjugated to, attached to, coated by, encompassed by or chemically otherwise associated with a natural or biological proteinaceous lipid. A natural or biological proteinaceous lipid refers to a naturally or biologically derived lipid or a lipid extracted from a natural or biological source, such as a once living organism, said lipid comprising one or more proteins such as the lipid (plasma) membrane of a melanocyte or melanosome). Optionally, each artificial melanin monomer, artificial melanin oligomer, and artificial melanin polymer of an artificial melanin nanoparticle, artificial melanin thin film, artificial melanin layer, and any compound, material, or formulation comprising any of these, is not bound to, conjugated to, attached to, coated by, encompassed by or otherwise chemically associated with a natural or biological lipid (e.g. a lipid bilayer, lipid membrane or phospholipid compound). A natural or biological lipid refers to a naturally or biologically derived lipid or a lipid extracted from a natural or biological source, such as a once living organism. Optionally, any artificial melanin monomer, artificial melanin oligomer, and artificial melanin polymer of an artificial melanin nanoparticle, artificial melanin thin film, artificial melanin layer, and any compound, material, or formulation comprising any of these, is bound to, conjugated to, attached to, coated by, encompassed by, and / or otherwise associated with a synthetic or artificial lipid or with a synthetic or artificial phospholipid. A synthetic or artificial lipid refers to a synthesized lipid that is not derived from or is not extracted from a natural or biological source, such as a once living organism.

[0034] The term “artificial melanin precursor” refers to a compound or material that can form an artificial melanin material after a chemical reaction, such as after a chemical reaction with an oxidation agent. An artificial melanin precursor can be, but is not necessarily, itself a melanin. For example, an artificial melanin precursor can be, but is not necessarily, a melanin monomer. For example, contacting artificial melanin precursors such as melanin monomers with an oxidizing agent can result in oxidativeoligomerization (or, polymerization) among the artificial melanin precursors thereby forming artificial melanin material(s).

[0035] The term “selenomelanin” refers to melanin comprising selenium. For example, a selenomelanin material comprises selenium. Optionally, a chemical formula of a selenomelanin material comprises selenium (e.g., at least one selenium atom).

[0036] In aspects, the term “pheomelanin” refers to a melanin whose chemical formula comprises at least one substituted or unsubstituted benzothiazine, at least one substituted or unsubstituted benzothiazole, at least one substituted or unsubstituted benzoselenazole, at least one substituted or unsubstituted benzoselenazine, at least one derivative of any of these, or any combination of these. In certain embodiments, the term pheomelanin refers to a melanin made from L-DOPA and cysteine, whose chemical formula comprises at least one substituted or unsubstituted benzothiazine, at least one substituted or unsubstituted benzothiazole, at least one substituted or unsubstituted benzoselenazole, at least one substituted or unsubstituted benzoselenazine, at least one derivative of any of these, or any combination of these. In certain embodiments, a selenium pheomelanin refers to a melanin whose chemical formula comprises at least one substituted or unsubstituted benzoselenazole, at least one substituted or unsubstituted benzoselenazine, at least one derivative of any of these, or any combination of these.

[0037] In aspects, the term “eumelanin” refers to a melanin whose chemical formula comprises at least one dihydoxyindole (DHI) (e.g., 5,6-dihydroxyindole), at least one dihydroxyindole-2-carboxylic acid (DHICA) (e.g., 5,6-dihydroxyindole-2-carboxylic acid), or a combination of these.

[0038] In aspects, the term “allomelanin” refers to a melanin that consists of nitrogen- free precursors, and whose chemical formula comprises at least one dihydroxynaphthalene (DHN) (e.g., 1 ,8-dihydroxynaphthalene), at least one catechol, or a combination of these.

[0039] The term “aging”, when used in reference to artificial melanin nanoparticles herein, refers to a process by which synthesized and isolated artificial melanin nanoparticles oxidize, and optionally further darker, over time during exposure to oxygen, such due to exposure to air. Isolated artificial melanin nanoparticles can be artificial melanin nanoparticles that are purified, such as by centrifugation, and redispersed in water, such as ultrapure water, or optionally another solvent or solvent solution. For example, artificial melanin nanoparticles may age if the particles are dispersed in water and are stored in a vial with the vial’s top on (closed) and with the top not being opened for some extended period of time, because there is residual oxygen in the container. The aging process can alter certain properties or characteristics of artificial melanin nanoparticles, such as increasing solubility in organic solvent or decreasing toxicity to certain living biological cells. For example, without wishing to be bound by any particular theory, in some embodiments, freshly synthesized artificial melanin nanoparticles can be dynamic and shed monomers or oligomers into a cell when internalized by the cell. For example, without wishing to be bound by any particular theory, in some embodiments, freshly synthesized artificial melanin nanoparticles can be dynamic and have surface chemistry oxidation state that is not optimal for living cells when internalized by cells. For example, without wishing to be bound by any particular theory, in some embodiments, the aging process can lead to more crosslinking or otherwise chemical association between melanin compounds (monomers, oligomers) in the artificial melanin nanoparticles, potentially leading to reduced cytotoxicity, such as due to reduced shedding of melanin compounds into the cell and / or altering or stabilizing of the particles’ surface chemistry.

[0040] The term “size characteristic” refers to a property, or set of properties, of a particle that directly or indirectly relates to a size attribute. According to some embodiments, a size characteristic corresponds to an empirically-derived size characteristic of a particle(s) being detected, such as a size characteristic based on, determined by, or corresponding to data from any technique or instrument that may be used to determine a particle size, such as electron microscope (e.g., SEM and TEM) or a light scattering technique (e.g., DLS). For example, a size characteristic can correspond to a spherical particle exhibiting similar or substantially same properties, such as aerodynamic, hydrodynamic, optical, and / or electrical properties, as the particle(s) being detected). According to some embodiments, a size characteristic corresponds to a physical dimension, such as a cross-sectional size (e.g., length, width, thickness, or diameter).

[0041] The term “particles” refers to small solid objects that may be dispersed and / or suspended in a fluid (e.g., liquid). For example, a slurry, a dispersion, and a suspension each include particles in a fluid. The terms “particle” and “particulate” may be usedinterchangeably. An exemplary particle is an artificial melanin nanoparticle. A plurality of particles may be associated together to form an agglomerate of particles. Generally, the term “particle”, such as “nanoparticle” or “melanin nanoparticle”, refers to an individual particle rather than to an agglomerate of such individual particles.

[0042] The term “dispersed” refers to species, such as particles, in a fluid forming a dispersion. As used herein, the term “dispersion” broadly refers to a mixture of one or more chemical species, such as particles, in a fluid, such as the art-recognized meaning of solution, dispersion, and / or suspension. The chemical species, such as particles, dispersed in a dispersion can be referred as a dispersed species. In some aspects, a dispersion is a mixture of particles, such as artificial melanin particles, in a liquid, such as a solvent. In some aspects, a dispersion is a homogeneous mixture. In the context of a dispersion, the term “homogeneous” refers to a liquid mixture that appears uniform to the naked eye. In contrast, a heterogenous liquid mixture includes particles that are precipitated from or suspended in the liquid mixture and are large enough to be distinctly identifiable by the naked eye in the liquid mixture. A heterogeneous liquid mixture includes, for example, sedimented and / or sedimenting particles. In some aspects, the term “dispersion” is broadly intended to include solutions and dispersions, such as colloids, which are not heterogenous liquid mixtures. In some aspects, a dispersion is a microscopically homogenous, or uniform, mixture of particles in a liquid, such as a solvent. In some aspects, a dispersion is thermodynamically favored remain stably dispersed or is thermodynamically favored to segregate by sedimentation but wherein sedimentation is kinetically slowed or prevented. Particles, of a dispersion, that are characterized as stably dispersed remain dispersed in the dispersion and do not sediment or precipitate out of the liquid, of the dispersion, for at least 5 hours, preferably at least 12 hours, preferably at least 24 hours, and more preferably at least 1 week, under normal temperature and pressure (NTP) and exposure to air. In some aspects, particles that are not or cannot be dispersed in a fluid refer to particles that form precipitates or sediments upon being mixed in the fluid.

[0043] The term “size stable” refers to stability of particles in a dispersion with respect to a size characteristic of said particles. Optionally, particles in a dispersion characterized as size stable are characterized by a size characteristic being within 50%, within 40%, within 30%, preferably within 20%, more preferably within 15%, still more preferably within 10%, further more preferably within 5%, or equivalent to a reference orinitial size characteristic, under given conditions and optionally for a given time. For example, nanoparticles of a dispersion characterized as size-stable in the dispersion having a pH of at least 11 , with respect to an average size of the nanoparticle in the dispersion having a pH of 7, have an average size in the pH 11 dispersion that is within 50%, within 40%, within 30%, preferably within 20%, more preferably within 15%, still more preferably within 10%, further more preferably within 5%, or equivalent to an average size of the otherwise equivalent nanoparticles in the otherwise equivalent dispersion having a pH of 7. Optionally, nanoparticles characterized as size stable as so size stable for time that is at least 1 hour to 5 hours, preferably at least 5 hours to 12 hours, more preferably at least 12 hours to 1 week, still more preferably at least 1 week.

[0044] The term “strong oxidizing agent” refers to a substance (e.g., compound, molecule, material) having a greater ability for subtracting, removing, or accepting one or more electron from another other substance compared to oxygen gas, including oxygen gas dissolved in a solution. The greater ability may be due to thermodynamic, kinetic, and / or electrochemical characteristics thereof. Optionally, a strong oxidizing agent has a greater or more positive standard electrode potential than O2.

[0045] The term “U” in a unit of concentration, such as “U / rnL”, refers to “unit of activity” and is a known term of art referring to enzyme catalytic activity. A unit “U” refers to the amount of enzyme that catalyzes the conversion of 1 micromole (pmole) of a substrate per minute. Thus, 1 enzyme unit (II) = 1 pmol / min, where pmol refers to the amount of substrate converted. Because each enzyme has a unique substrate, a unit of activity is different for one enzyme versus another.

[0046] The term “structural color” refers to the generation of color due to interference of visible light structural features, such as a film or layer or a microstructured surface. A layer of melanin nanoparticles may exhibit color due to interference of visible light with the microstructure of the layer, rather than solely due to pigmentation. Without wishing to be bound by any particular theory, the effect of structural color can enable a spectrum on non-fading, non-photobleaching colors which can be iridescent or non-iridescent. Without wishing to be bound by any particular theory, high refractive index of melanin and synthetic melanin, and its broadband absorption across the visible spectrum allows it to interact with light in such a way that a multitude of colors are produced.

[0047] The term “peak size” size refers to the statistical mode, or peak frequency, of a particle size distribution, or the particle size most commonly found in the particle size distribution. A particle size distribution can be measured using dynamic light scattering, for example.

[0048] The term "sphere" as used herein, in the usual and customary sense, refers to a round or substantially round geometrical object in three-dimensional space that is substantially the surface of a completely round ball, analogous to a circular object in two dimensions. A sphere may be defined mathematically as the set of points that are all at the same or substantially all at the same distance r from a given point, but in three- dimensional space, where r is the radius of the mathematical ball and the given point is the center or substantially the center of the mathematical ball. In embodiments, the longest straight line through the ball, connecting two points of the sphere, passes through the center and its length is thus twice the radius; it is a diameter of the ball. A nanosphere is a nanoparticle having a radius of less than 1 pm.

[0049] The term “sphericity” may be used to describe a given particle, such as a nanoparticle, and refers to a ratio of surface area of a sphere (having the same volume as the given particle) to the surface area of the particle. An ideal sphere has a sphericity of 1 . For example, an ideal cylinder has a sphericity of approximately 0.874.

[0050] The terms "ultraviolet induced damage" and "UV induced damage" as used interchangeably herein refer, in the usual and customary sense, to chemical and / or structural changes attending irradiation of UV light of sufficient energy. In some aspects, UV induced damage is the result of exposure to UVA, UVB, and / or UVC wavelengths. UV induced damage can include scission of nucleic acids (e.g., DNA or RNA), breaking of bonds in proteins, lipids, and other physiological molecules, and degradation of (e.g., polymer chain scission) or additional crosslinking in polymeric materials. For example, the damage can be damage resulting from the formation of reactive species, such as reactive oxygen species (ROS), or direct photolytic effects (e.g., molecule break down or change due to the absorption of light energy). In some aspects, UV induced damage is assessed by measuring the changes in surface chemistry of a polymeric material (e.g., changes in carbon bond populations).

[0051] The terms "reactive oxygen species" and "ROS" as used interchangeably herein refer, in the usual and customary sense, to transient species, typically formedduring exposure to radiation (e.g., UV irradiation or gamma irradiation) capable of inducing oxidative decomposition.

[0052] The terms "gamma ray induced damage" and "y-ray induced damage" as used interchangeably herein refer, in the usual and customary sense, to chemical and / or structural changes attending irradiation with gamma rays of sufficient energy. Gamma ray induced damage can include ionization of atoms and molecules, disruption of molecular bonds, biological molecules, or polymeric materials, such as polymer chain scission, additional crosslinking, and / or the formation of defects in crystalline structures. For example, the gamma ray induced damage can include damage resulting from ionizing radiation or the production of reactive species, such as free radicals.

[0053] The term, “mechanical property” refers, in the usual and customary sense, to a physical characteristic of a material that defines its response to a mechanical force or deformation. In some aspects, mechanical property includes, but is not limited to, ultimate tensile strength, elongation at break, toughness, elasticity, hardness, flexural strength, compressive strength, impact resistance, and / or thermomechanical properties such as thermal expansion, heat deflection temperature, and glass transition temperature. In some aspects, mechanical property refers to a material’s behavior under environmental stresses, such as radiation resistance, fatigue resistance, creep, and other stresses. For example, in the case of a polymeric material, mechanical properties may describe ultimate tensile strength, elongation, toughness, elasticity, resistance to UV induced damage, resistance to gamma ray induced damage, and / or the ability to maintain performance under varying thermal and mechanical loads. For example, in the case of a polymeric material, mechanical properties may describe resistance to photoinduced cracks on the surface of the polymeric material.

[0054] The term “self-assembly” refers to a process in which individual elements assemble into a network or organized structure without external direction. In an embodiment, self-assembly leads to a decrease in entropy of a system. In an embodiment, self-assembly may be induced, or initiated, via contacting or reacting the individual elements, optionally at a certain critical concentration, and / or via temperature and / or via pressure. A “self-assembled structure” is a structure or network formed by self-assembly. In an embodiment, self-assembly is a polymer crystallization process. The Gibbs free energy of the self-assembled structure is lower than of the sum of the individual components in their non-organized arrangement prior to self-assembly underotherwise identical conditions (e.g., temperature and pressure). In an embodiment, entropy of a self-assembled structure is lower than that of the sum of the individual components in their non-organized arrangement prior to self-assembly under otherwise identical conditions (e.g., temperature and pressure). For example, artificial melanin nanoparticles of this disclosure can form by self-assembly of a plurality of oligomers and / or melanin monomers. For example, structures or layers (e.g., films) for artificial melanin nanoparticles may form by self-assembly, such as structures or layers formed of artificial melanin nanoparticles and exhibiting structural color.

[0055] The term “substantially” refers to a property, condition, or value that is within 20%, 10%, within 5%, within 1 %, optionally within 0.1 %, or is equivalent to a reference property, condition, or value. The term “substantially equal”, “substantially equivalent”, or “substantially unchanged”, when used in conjunction with a reference value describing a property or condition, refers to a value that is within 20%, within 10%, optionally within 5%, optionally within 1 %, optionally within 0.1 %, or optionally is equivalent to the provided reference value. For example, a diameter is substantially equal to 100 nm (or, “is substantially 100 nm”) if the value of the diameter is within 20%, optionally within 10%, optionally within 5%, optionally within 1 %, within 0.1 %, or optionally equal to 100 nm. The term “substantially greater”, when used in conjunction with a reference value describing a property or condition, refers to a value that is at least 1 %, optionally at least 5%, optionally at least 10%, or optionally at least 20% greater than the provided reference value. The term “substantially less”, when used in conjunction with a reference value describing a property or condition, refers to a value that is at least 1 %, optionally at least 5%, optionally at least 10%, or optionally at least 20% less than the provided reference value.

[0056] The term "contacting" may include allowing two species to react, interact, or physically touch, wherein the two species may be, for example, a nanoadditive (e.g., an allomelanin-inspired nanoadditive) as provided herein and at least a portion of a polymeric material or a subcomponent thereof. In aspects, contacting includes, for example, allowing a nanoadditive as described herein to interact with a first subcomponent of a polymeric material (e.g., an isocyanate component of a polyurethane).

[0057] The terms "analog" and "analogue" are used interchangeably and are used in accordance with their plain ordinary meaning within Chemistry and Biology and refers toa chemical compound that is structurally similar to another compound (i.e., a so-called "reference" compound) but differs in composition, e.g., in the replacement of one atom by an atom of a different element, or in the presence of a particular functional group, or the replacement of one functional group by another functional group, or the absolute stereochemistry of one or more chiral centers of the reference compound, including isomers thereof. Accordingly, an analog is a compound that is similar or comparable in function and appearance but not in structure or origin to a reference compound.

[0058] Except where otherwise specified, the term “molecular weight” refers to an average molecular weight. Except where otherwise specified, the term “average molecular weight,” refers to number-average molecular weight. Number average molecular weight is defined as the total weight of a sample volume divided by the number of molecules within the sample. As is customary and well known in the art, peak average molecular weight and weight average molecular weight may also be used to characterize the molecular weight of the distribution of polymers within a sample.

[0059] The term “weight-average molecular weight” (Mw) refers to the average molecular weight defined as the sum of the products of the molecular weight of each polymer molecule (Mi) multiplied by its weight fraction (wi): Mw= ZwiMi. As is customary and well known in the art, peak average molecular weight and number average molecular weight may also be used to characterize the molecular weight of the distribution of polymers within a sample.

[0060] The term “wt.%” or “wt%” refers to a weight percent, or a mass fraction represented as a percentage by mass. The term “at.%” or “at%” refers to an atomic percent, or an atomic ratio represented as a percentage of a type of atom with respect to total atoms in a given matter, such as a molecule, compound, material, nanoparticle, polymer, dispersion, etc.

[0061] The term “oligomerization” refers to a chemical process of converting a monomer or a mixture of monomers into an oligomer. The term “oxidative oligomerization” refers to a chemical process of oligomerization that includes chemical oxidation of one or more monomers to form an oligomer. An oligomerization is a polymerization process, wherein an oligomer is formed as a result of the polymerization.

[0062] As used herein, the term “polymer” refers to a molecule composed of repeating structural units connected by covalent chemical bonds often characterized bya number of repeating units, also referred to as base units (e.g., greater than or equal to 2 base units). As used herein, a term “polymer” is inclusive of an “oligomer” (i.e. , an oligomer is a polymer; i.e., a polymer is optionally an oligomer). An “oligomer” refers to a molecule composed of repeating structural units, also referred to as base units, connected by covalent chemical bonds often characterized by a number of repeating units less such that the oligomer is a low molecular weight polymer. Optionally, for example, an oligomer has equal to or less than 100 repeating units. Optionally, for example, an oligomer has a lower molecular weight less than or equal to 10,000 Da. Oligomers may be the polymerization product of one or more monomer precursors. Polymerization of one or more monomers, or monomer precursors, resulting in formation of an oligomer may be referred to as oligomerization. An oligomer optionally includes 100 or less, 50 or less, 15 or less, 12 or less, 10 or less, or 5 or less repeating units (or, “base units”). An oligomer may be characterized has having a molecular weight of 10,000 Da or less, 5,000 Da or less, 1 ,000 Da or less, 500 Da or less, or 200 Da or less. A dimer, a trimer, a tetramer, or a pentamer is an oligomer having two, three, four, or five, respectively, repeating units, or base units. Polymers can have, for example, greater than 100 repeating units. Polymers can have, for example, a high molecular weight, such as greater than 10,000 Da, in some embodiments greater than or equal to 50,000 Da or greater than or equal to 100,000 Da. The term polymer includes homopolymers, or polymers consisting essentially of a single repeating monomer subunit. The term polymer also includes copolymers which are formed when two or more different types of monomers are linked in the same polymer. Copolymers may comprise two or more monomer subunits, and include random, block, brush, brush block, alternating, segmented, grafted, tapered and other architectures. Useful polymers include organic polymers or inorganic polymers that may be in amorphous, semi-amorphous, crystalline or semi-crystalline states. Polymer side chains capable of cross linking polymers (e.g., physical cross linking) may be useful for some applications.

[0063] As used herein, the term “polymeric material” refers to a substance or material comprising at least one polymer, such as a copolymer. In some aspects, polymeric material is formed through the chemical reaction of two or more subcomponents, such as monomers, oligomers, or prepolymers. In some aspects, the polymeric material is a thermosetting material, a thermoplastic material, an elastomer, a resin, or a blend thereof. In some aspects, polymeric material refers to a material comprising two or more polymer components. In some aspects, for example, a polymeric material comprises ablock copolymer and one or more additional block copolymers, homopolymers, copolymers, brush copolymers, brush block copolymers, oligomers, solvent, small molecules (e.g., molecular weight less than 500 Da, optionally less than 100 Da), or any combination of these. In aspects, polymeric material comprises a first block copolymer, and one or more additional components comprising polymers, block copolymers, brush polymers, linear block copolymers, random copolymers, homopolymers, or any combinations of these. Polymeric material includes mixtures of two, three, four, five and more polymer subcomponents. Polymeric material includes both natural and synthetic polymers. Polymeric material may be unmodified or chemically or physical modified, such as through cross-linking or functionalization. Polymeric material includes, but is not limited to, materials such as polyurethane, polyolefins, polyesters, polyamides, polycarbonates, and blends thereof.

[0064] An “oligomer” refers to a molecule composed of repeating structural units, also referred to as base units, connected by covalent chemical bonds often characterized by a number of repeating units less than that of a polymer (e.g., equal to or less than 100 repeating units) and a lower molecular weights (e.g. less than or equal to 10,000 Da) than polymers. Oligomers may be the polymerization product of one or more monomer precursors. Polymerization of one or more monomers, or monomer precursors, resulting in formation of an oligomer may be referred to as oligomerization. An oligomer optionally includes 100 or less, 50 or less, 15 or less, 12 or less, 10 or less, or 5 or less repeating units (or, “base units”). An oligomer may be characterized has having a molecular weight of 10,000 Da or less, 5,000 Da or less, 1 ,000 Da or less, 500 Da or less, or 200 Da or less. A dimer, a trimer, a tetramer, or a pentamer is an oligomer having two, three, four, or five, respectively, repeating units, or base units.

[0065] As used herein, the term “group” may refer to a functional group of a chemical compound. Groups of the present compounds refer to an atom or a collection of atoms that are a part of the compound. Groups of the present invention may be attached to other atoms of the compound via one or more covalent bonds. Groups may also be characterized with respect to their valence state. The present invention includes groups characterized as monovalent, divalent, trivalent, etc. valence states.

[0066] The term “moiety” refers to a group, such as a functional group, of a chemical compound or molecule. A moiety is a collection of atoms that are part of the chemical compound or molecule. The present invention includes moieties characterized asmonovalent, divalent, trivalent, etc. valence states. Generally, but not necessarily, a moiety comprises more than one functional group.

[0067] As used herein, the term “subcomponent” when used in reference a polymeric material, refers to a constituent used in the preparation of a polymeric material, wherein the subcomponent reacts with one or more other subcomponents to form the polymeric material. In some aspects, a subcomponent is a monomer, an oligomer, a prepolymer, or other reactive species. For example, in the context of polyurethane materials, the subcomponents may comprise an isocyanate subcomponent and a polyol subcomponent.

[0068] As used herein, the term “substituted” refers to a compound wherein one or more hydrogens is replaced by another functional group, provided that the designated atom’s normal valence is not exceeded. An exemplary substituent includes, but is not limited to: a halogen or halide, an alkyl, a cycloalkyl, an aryl, a heteroaryl, an acyl, an alkoxy, an alkenyl, an alkynyl, an alkylaryl, an arylene, a heteroarylene, an alkenylene, a cycloalkenylene, an alkynylene, a hydroxyl (-OH), a carbonyl (RCOR’), a sulfide (e.g., RSR’), a phosphate (ROP(=O)(OH)2), an azo (RNNR’), a cyanate (ROCN), an amine (e.g., primary, secondary, or tertiary), an imine (RC(=NH)R'), a nitrile (RON), a pyridinyl (or pyridyl), a diamine, a triamine, an azide, a diimine, a triimine, an amide, a diimide, or an ether (ROR’); where each of R and R’ is independently a hydrogen or a substituted or unsubstituted alkyl group, aryl group, alkenyl group, or a combination of these. Optional substituent functional groups are also described below. In some embodiments, the term substituted refers to a compound wherein each of more than one hydrogen is replaced by another functional group, such as a halogen group. For example, when the substituent is oxo (i.e., =0), then two hydrogens on the atom are replaced. The substituent group can be any substituent group described herein. For example, substituent groups can include one or more of a hydroxyl, an amino (e.g., primary, secondary, or tertiary), an aldehyde, a carboxylic acid, an ester, an amide, a ketone, nitro, an urea, a guanidine, cyano, fluoroalkyl (e.g., trifluoromethane), halo (e.g., fluoro), aryl (e.g., phenyl), heterocyclyl or heterocyclic group (i.e., cyclic group, e.g., aromatic (e.g., heteroaryl) or non-aromatic where the cyclic group has one or more heteroatoms), oxo, or combinations thereof. Combinations of substituents and / or variables are permissible provided that the substitutions do not significantly adversely affect synthesis or use of the compound.

[0069] As used herein, the term “derivative” refers to a compound wherein an atom or functional group is replaced by another atom or functional group (e.g., a substituent function group as also described below), including, but not limited to: a hydrogen, a halogen or halide, an alkyl, a cycloalkyl, an aryl, a heteroaryl, an acyl, an alkoxy, an alkenyl, an alkynyl, an alkylaryl, an arylene, a heteroarylene, an alkenylene, a cycloalkenylene, an alkynylene, a hydroxyl (-OH), a carbonyl (RCOR’), a sulfide (e.g., RSR’), a phosphate (ROP(=O)(OH)2), an azo (RNNR’), a cyanate (ROCN), an amine (e.g., primary, secondary, or tertiary), an imine (RC(=NH)R'), a nitrile (RCN), a pyridinyl (or pyridyl), a diamine, a triamine, an azide, a diimine, a triimine, an amide, a diimide, or an ether (ROR’); where each of R and R’ is independently a hydrogen or a substituted or unsubstituted alkyl group, aryl group, alkenyl group, or a combination of these. Optional substituent functional groups are also described below. Optionally, the term “derivative” refers to a compound wherein one or two atoms or functional groups are independently replaced by another atom or functional group. Optionally, the term derivative does not refer to or include replacement of a chalcogen atom (S, Se) that is a member of a heterocyclic group. Optionally, and unless otherwise stated, the term derivative does not refer to or include replacement of a chalcogen atom (S, Se) nor a N (nitrogen) where the chalcogen atom and the N are members same heterocyclic group. Optionally, but not necessarily, the term derivative does not include breaking a ring structure, replacement of a ring member, or removal of a ring member.

[0070] As is customary and well known in the art, hydrogen atoms in formula, are not always explicitly shown, for example, hydrogen atoms bonded to the carbon atoms of aromatic, heteroaromatic, and alicyclic rings are not always explicitly shown. The structures provided herein, for example in the context of the description of formula and schematics and structures in the drawings, are intended to convey to one of reasonable skill in the art the chemical composition of compounds of the methods and compositions of the invention, and as will be understood by one of skill in the art, the structures provided do not indicate the specific positions and / or orientations of atoms and the corresponding bond angles between atoms of these compounds.

[0071] As used herein, the terms “alkylene” and “alkylene group” are used synonymously and refer to a divalent group derived from an alkyl group as defined herein. The invention includes compounds having one or more alkylene groups. Alkylene groups in some compounds function as linking and / or spacer groups. Compounds of the invention may have substituted and / or unsubstituted C1-C20 alkylene,Ci-C alkylene and C1-C5 alkylene groups, for example, as one or more linking groups (e.g. L1- L6).

[0072] As used herein, the terms “cycloalkylene” and “cycloalkylene group” are used synonymously and refer to a divalent group derived from a cycloalkyl group as defined herein. The invention includes compounds having one or more cycloalkylene groups. Cycloalkyl groups in some compounds function as linking and / or spacer groups. Compounds of the invention may have substituted and / or unsubstituted C3-C20 cycloalkylene, C3-C10 cycloalkylene and C3-C5 cycloalkylene groups, for example, as one or more linking groups (e.g. L1- L6).

[0073] As used herein, the terms “arylene” and “arylene group” are used synonymously and refer to a divalent group derived from an aryl group as defined herein. The invention includes compounds having one or more arylene groups. In some embodiments, an arylene is a divalent group derived from an aryl group by removal of hydrogen atoms from two intra-ring carbon atoms of an aromatic ring of the aryl group. Arylene groups in some compounds function as linking and / or spacer groups. Arylene groups in some compounds function as chromophore, fluorophore, aromatic antenna, dye and / or imaging groups. Compounds of the invention include substituted and / or unsubstituted C3-C30 arylene, C3-C20 arylene, C3-C10 arylene and C1-C5 arylene groups, for example, as one or more linking groups (e.g. L1- L6).

[0074] As used herein, the terms “heteroarylene” and “heteroarylene group” are used synonymously and refer to a divalent group derived from a heteroaryl group as defined herein. The invention includes compounds having one or more heteroarylene groups. In an embodiment, a heteroarylene is a divalent group derived from a heteroaryl group by removal of hydrogen atoms from two intra-ring carbon atoms or intra-ring nitrogen atoms of a heteroaromatic or aromatic ring of the heteroaryl group. Heteroarylene groups in some compounds function as linking and / or spacer groups. Heteroarylene groups in some compounds function as chromophore, aromatic antenna, fluorophore, dye and / or imaging groups. Compounds of the invention include substituted and / or unsubstituted C3-C30 heteroarylene, C3-C20 heteroarylene, C1-C10 heteroarylene and C3- Cs heteroarylene groups, for example, as one or more linking groups (e.g. L1- L6).

[0075] As used herein, the terms “alkenylene” and “alkenylene group” are used synonymously and refer to a divalent group derived from an alkenyl group as defined herein. The invention includes compounds having one or more alkenylene groups.Alkenylene groups in some compounds function as linking and / or spacer groups. Compounds of the invention include substituted and / or unsubstituted C2-C20 alkenylene, C2-C10 alkenylene and C2-C5 alkenylene groups, for example, as one or more linking groups (e.g. L1- L6).

[0076] As used herein, the terms “cylcoalkenylene” and “cylcoalkenylene group” are used synonymously and refer to a divalent group derived from a cylcoalkenyl group as defined herein. The invention includes compounds having one or more cylcoalkenylene groups. Cycloalkenylene groups in some compounds function as linking and / or spacer groups. Compounds of the invention include substituted and / or unsubstituted C3-C20 cylcoalkenylene, C3-C10 cylcoalkenylene and C3-C5 cylcoalkenylene groups, for example, as one or more linking groups (e.g. L1- L6).

[0077] As used herein, the terms “alkynylene” and “alkynylene group” are used synonymously and refer to a divalent group derived from an alkynyl group as defined herein. The invention includes compounds having one or more alkynylene groups. Alkynylene groups in some compounds function as linking and / or spacer groups. Compounds of the invention include substituted and / or unsubstituted C2-C20 alkynylene, C2-C10 alkynylene and C2-C5 alkynylene groups, for example, as one or more linking groups (e.g. L1- L6).

[0078] As used herein, the term “halo” refers to a halogen group such as a fluoro (- F), chloro (-CI), bromo (-Br), iodo (-I) or astato (-At).

[0079] The term "heterocyclic" refers to ring structures containing at least one other kind of atom, in addition to carbon, in the ring. Examples of such heteroatoms include nitrogen, oxygen and sulfur. Heterocyclic rings include heterocyclic alicyclic rings and heterocyclic aromatic rings. Examples of heterocyclic rings include, but are not limited to, pyrrolidinyl, piperidyl, imidazolidinyl, tetrahydrofuryl, tetrahydrothienyl, furyl, thienyl, pyridyl, quinolyl, isoquinolyl, pyridazinyl, pyrazinyl, indolyl, imidazolyl, oxazolyl, thiazolyl, pyrazolyl, pyridinyl, benzoxadiazolyl, benzothiadiazolyl, triazolyl and tetrazolyl groups. Atoms of heterocyclic rings can be bonded to a wide range of other atoms and functional groups, for example, provided as substituents.

[0080] The term “carbocyclic” refers to ring structures containing only carbon atoms in the ring. Carbon atoms of carbocyclic rings can be bonded to a wide range of other atoms and functional groups, for example, provided as substituents.

[0081] The term “alicyclic ring” refers to a ring, or plurality of fused rings, that is not an aromatic ring. Alicyclic rings include both carbocyclic and heterocyclic rings.

[0082] The term “aromatic ring” refers to a ring, or a plurality of fused rings, that includes at least one aromatic ring group. The term aromatic ring includes aromatic rings comprising carbon, hydrogen and heteroatoms. Aromatic ring includes carbocyclic and heterocyclic aromatic rings. Aromatic rings are components of aryl groups.

[0083] The term “fused ring” or “fused ring structure” refers to a plurality of alicyclic and / or aromatic rings provided in a fused ring configuration, such as fused rings that share at least two intra ring carbon atoms and / or heteroatoms.

[0084] As used herein, the term "alkoxyalkyl" refers to a substituent of the formula alkyl-O-alkyl.

[0085] As used herein, the term "polyhydroxyalkyl" refers to a substituent having from 2 to 12 carbon atoms and from 2 to 5 hydroxyl groups, such as the 2,3-dihydroxypropyl, 2,3,4-trihydroxybutyl or 2,3,4, 5-tetrahydroxypentyl residue.

[0086] As used herein, the term "polyalkoxyalkyl" refers to a substituent of the formula alkyl-(alkoxy)n-alkoxy wherein n is an integer from 1 to 10, preferably 1 to 4, and more preferably for some embodiments 1 to 3.

[0087] Amino acids include glycine, alanine, valine, leucine, isoleucine, methionine, proline, phenylalanine, tryptophan, asparagine, glutamine, glycine, serine, threonine, serine, rhreonine, asparagine, glutamine, tyrosine, cysteine, lysine, arginine, histidine, aspartic acid and glutamic acid. As used herein, reference to “a side chain residue of a natural a-amino acid” specifically includes the side chains of the above-referenced amino acids. Peptides and peptide moieties, as used and described herein, comprise two or more amino acid groups connected via peptide bonds.

[0088] Amino acids and amino acid groups refer to naturally-occurring amino acids, unnatural (non-naturally occurring) amino acids, and / or combinations of these. Naturally-occurring amino acids are those encoded by the genetic code, as well as those amino acids that are later modified, e.g., hydroxyproline, y-carboxyglutamate, and O-phosphoserine. Naturally-occurring a-amino acids include, without limitation, alanine (Ala), cysteine (Cys), aspartic acid (Asp), glutamic acid (Glu), phenylalanine (Phe), glycine (Gly), histidine (His), isoleucine (lie), arginine (Arg), lysine (Lys), leucine (Leu), methionine (Met), asparagine (Asn), proline (Pro), glutamine (Gin), serine (Ser),threonine (Thr), valine (Vai), tryptophan (Trp), tyrosine (Tyr), and combinations thereof. Stereoisomers of a naturally-occurring a-amino acids include, without limitation, D- alanine (D-Ala), D-cysteine (D-Cys), D-aspartic acid (D-Asp), D-glutamic acid (D-Glu), D-phenylalanine (D-Phe), D-histidine (D-His), D-isoleucine (D-lle), D-arginine (D-Arg), D-lysine (D-Lys), D-leucine (D-Leu), D-methionine (D-Met), D-asparagine (D-Asn), D- proline (D-Pro), D-glutamine (D-GIn), D-serine (D-Ser), D-threonine (D-Thr), D-valine (D- Val), D-tryptophan (D-Trp), D-tyrosine (D-Tyr), and combinations thereof.

[0089] Unnatural (non-naturally occurring) amino acids include, without limitation, amino acid analogs, amino acid mimetics, synthetic amino acids, / V-substituted glycines, and / V-methyl amino acids in either the L- or D-configuration that function in a manner similar to the naturally-occurring amino acids. For example, “amino acid analogs” can be unnatural amino acids that have the same basic chemical structure as naturally- occurring amino acids (i.e., a carbon that is bonded to a hydrogen, a carboxyl group, an amino group) but have modified side-chain groups or modified peptide backbones, e.g., homoserine, norleucine, methionine sulfoxide, methionine methyl sulfonium. “Amino acid mimetics” refer to chemical compounds that have a structure that is different from the general chemical structure of an amino acid, but that functions in a manner similar to a naturally-occurring amino acid. Amino acids may be referred to herein by either the commonly known three letter symbols or by the one-letter symbols recommended by the IUPAC-IUB Biochemical Nomenclature Commission.

[0090] The terms “monomer unit,” “repeating monomer unit,” “repeating unit,” and “polymerized monomer” can be used interchangeably and refer to a monomeric portion of a polymer described herein which is derived from or is a product of polymerization of one individual “monomer” or “polymerizable monomer.” Each individual monomer unit of a polymer is derived from or is a product of polymerization of one polymerizable monomer. Each individual “monomer unit” or “repeating unit” of a polymer comprises one (polymerized) polymer backbone group. For example, in a polymer that comprises monomer units X and Y arranged as X-Y-X-Y-X-Y-X-Y (where each X is identical to each other X and each Y is identical to each other Y), each X and each Y is independently can be referred to as a repeating unit or monomer unit.

[0091] Alkyl groups include straight-chain, branched and cyclic alkyl groups. Alkyl groups include those having from 1 to 30 carbon atoms. Alkyl groups include small alkyl groups having 1 to 3 carbon atoms. Alkyl groups include medium length alkyl groupshaving from 4-10 carbon atoms. Alkyl groups include long alkyl groups having more than 10 carbon atoms, particularly those having 10-30 carbon atoms. The term cycloalkyl specifically refers to an alky group having a ring structure such as ring structure comprising 3-30 carbon atoms, optionally 3-20 carbon atoms and optionally 2 - 10 carbon atoms, including an alkyl group having one or more rings. Cycloalkyl groups include those having a 3-, 4-, 5-, 6-, 7-, 8-, 9- or 10- member carbon ring(s) and particularly those having a 3-, 4-, 5-, 6-, 7-, or 8- member ring(s). The carbon rings in cycloalkyl groups can also carry alkyl groups. Cycloalkyl groups can include bicyclic and tricycloalkyl groups. Alkyl groups are optionally substituted. Substituted alkyl groups include among others those which are substituted with aryl groups, which in turn can be optionally substituted. Specific alkyl groups include methyl, ethyl, n-propyl, iso-propyl, cyclopropyl, n-butyl, s-butyl, t-butyl, cyclobutyl, n-pentyl, branched-pentyl, cyclopentyl, n- hexyl, branched hexyl, and cyclohexyl groups, all of which are optionally substituted. Substituted alkyl groups include fully halogenated or semihalogenated alkyl groups, such as alkyl groups having one or more hydrogens replaced with one or more fluorine atoms, chlorine atoms, bromine atoms and / or iodine atoms. Substituted alkyl groups include fully fluorinated or semifluorinated alkyl groups, such as alkyl groups having one or more hydrogens replaced with one or more fluorine atoms. An alkoxy group is an alkyl group that has been modified by linkage to oxygen and can be represented by the formula R-0 and can also be referred to as an alkyl ether group. Examples of alkoxy groups include, but are not limited to, methoxy, ethoxy, propoxy, butoxy and heptoxy. Alkoxy groups include substituted alkoxy groups wherein the alky portion of the groups is substituted as provided herein in connection with the description of alkyl groups. As used herein MeO- refers to CH3O-. Compositions of some embodiments of the invention comprise alkyl groups as terminating groups, such as polymer backbone terminating groups and / or polymer side chain terminating groups. Substituted alkyl groups may include substitution to incorporate one or more silyl groups, for example wherein one or more carbons are replaced by Si.

[0092] Alkenyl groups include straight-chain, branched and cyclic alkenyl groups. Alkenyl groups include those having 1 , 2 or more double bonds and those in which two or more of the double bonds are conjugated double bonds. Alkenyl groups include those having from 2 to 20 carbon atoms. Alkenyl groups include small alkenyl groups having 2 to 3 carbon atoms. Alkenyl groups include medium length alkenyl groups having from 4- 10 carbon atoms. Alkenyl groups include long alkenyl groups having more than 10carbon atoms, particularly those having 10-20 carbon atoms. Cycloalkenyl groups include those in which a double bond is in the ring or in an alkenyl group attached to a ring. The term cycloalkenyl specifically refers to an alkenyl group having a ring structure, including an alkenyl group having a 3-, 4-, 5-, 6-, 7-, 8-, 9- or 10-member carbon ring(s) and particularly those having a 3-, 4-, 5-, 6- or 7-member ring(s). The carbon rings in cycloalkenyl groups can also carry alkyl groups. Cycloalkenyl groups can include bicyclic and tricyclic alkenyl groups. Alkenyl groups are optionally substituted.Substituted alkenyl groups include among others those which are substituted with alkyl or aryl groups, which groups in turn can be optionally substituted. Specific alkenyl groups include ethenyl, prop-1-enyl, prop-2-enyl, cycloprop-1 -enyl, but-1-enyl, but-2- enyl, cyclobut-1-enyl, cyclobut-2-enyl, pent-1 -enyl, pent-2-enyl, branched pentenyl, cyclopent-1 -enyl, hex-1 -enyl, branched hexenyl, cyclohexenyl, all of which are optionally substituted. Substituted alkenyl groups include fully halogenated or semihalogenated alkenyl groups, such as alkenyl groups having one or more hydrogens replaced with one or more fluorine atoms, chlorine atoms, bromine atoms and / or iodine atoms. Substituted alkenyl groups include fully fluorinated or semifluorinated alkenyl groups, such as alkenyl groups having one or more hydrogen atoms replaced with one or more fluorine atoms. Compositions of some embodiments of the invention comprise alkenyl groups as terminating groups, such as polymer backbone terminating groups and / or polymer side chain terminating groups.

[0093] Aryl groups include groups having one or more 5-, 6- 7-, or 8- member aromatic rings, including heterocyclic aromatic rings. The term heteroaryl specifically refers to aryl groups having at least one 5-, 6- 7-, or 8- member heterocyclic aromatic rings. Aryl groups can contain one or more fused aromatic rings, including one or more fused heteroaromatic rings, and / or a combination of one or more aromatic rings and one or more nonaromatic rings that may be fused or linked via covalent bonds. Heterocyclic aromatic rings can include one or more N, O, or S atoms in the ring. Heterocyclic aromatic rings can include those with one, two or three N atoms, those with one or two O atoms, and those with one or two S atoms, or combinations of one or two or three N, O or S atoms. Aryl groups are optionally substituted. Substituted aryl groups include among others those that are substituted with alkyl or alkenyl groups, which groups in turn can be optionally substituted. Specific aryl groups include phenyl, biphenyl groups, pyrrolidinyl, imidazolidinyl, tetrahydrofuryl, tetrahydrothienyl, furyl, thienyl, pyridyl, quinolyl, isoquinolyl, pyridazinyl, pyrazinyl, indolyl, imidazolyl, oxazolyl, thiazolyl,pyrazolyl, pyridinyl, benzoxadiazolyl, benzothiadiazolyl, and naphthyl groups, all of which are optionally substituted. Substituted aryl groups include fully halogenated or semihalogenated aryl groups, such as aryl groups having one or more hydrogens replaced with one or more fluorine atoms, chlorine atoms, bromine atoms and / or iodine atoms. Substituted aryl groups include fully fluorinated or semifluorinated aryl groups, such as aryl groups having one or more hydrogens replaced with one or more fluorine atoms. Aryl groups include, but are not limited to, aromatic group-containing or heterocylic aromatic group-containing groups corresponding to any one of the following: benzene, naphthalene, naphthoquinone, diphenylmethane, fluorene, anthracene, anthraquinone, phenanthrene, tetracene, tetracenedione, pyridine, quinoline, isoquinoline, indoles, isoindole, pyrrole, imidazole, oxazole, thiazole, pyrazole, pyrazine, pyrimidine, purine, benzimidazole, furans, benzofuran, dibenzofuran, carbazole, acridine, acridone, phenanthridine, thiophene, benzothiophene, dibenzothiophene, xanthene, xanthone, flavone, coumarin, azulene or anthracycline. As used herein, a group corresponding to the groups listed above expressly includes an aromatic or heterocyclic aromatic group, including monovalent, divalent and polyvalent groups, of the aromatic and heterocyclic aromatic groups listed herein are provided in a covalently bonded configuration in the compounds of the invention at any suitable point of attachment. In embodiments, aryl groups contain between 5 and 30 carbon atoms. In embodiments, aryl groups contain one aromatic or heteroaromatic six-member ring and one or more additional five- or six-member aromatic or heteroaromatic ring. In embodiments, aryl groups contain between five and eighteen carbon atoms in the rings. Aryl groups optionally have one or more aromatic rings or heterocyclic aromatic rings having one or more electron donating groups, electron withdrawing groups and / or targeting ligands provided as substituents. Compositions of some embodiments of the invention comprise aryl groups as terminating groups, such as polymer backbone terminating groups and / or polymer side chain terminating groups.

[0094] Arylalkyl groups are alkyl groups substituted with one or more aryl groups wherein the alkyl groups optionally carry additional substituents and the aryl groups are optionally substituted. Specific alkylaryl groups are phenyl-substituted alkyl groups, e.g., phenylmethyl groups. Alkylaryl groups are alternatively described as aryl groups substituted with one or more alkyl groups wherein the alkyl groups optionally carry additional substituents and the aryl groups are optionally substituted. Specific alkylaryl groups are alkyl-substituted phenyl groups such as methylphenyl. Substituted arylalkylgroups include fully halogenated or semihalogenated arylalkyl groups, such as arylalkyl groups having one or more alkyl and / or aryl groups having one or more hydrogens replaced with one or more fluorine atoms, chlorine atoms, bromine atoms and / or iodine atoms. Compositions of some embodiments of the invention comprise arylalkyl groups as terminating groups, such as polymer backbone terminating groups and / or polymer side chain terminating groups.

[0095] As to any of the groups described herein which contain one or more substituents, it is understood that such groups do not contain any substitution or substitution patterns which are sterically impractical and / or synthetically non-feasible. . In addition, the compounds of this invention include all stereochemical isomers arising from the substitution of these compounds. Optional substitution of alkyl groups includes substitution with one or more alkenyl groups, aryl groups or both, wherein the alkenyl groups or aryl groups are optionally substituted. Optional substitution of alkenyl groups includes substitution with one or more alkyl groups, aryl groups, or both, wherein the alkyl groups or aryl groups are optionally substituted. Optional substitution of aryl groups includes substitution of the aryl ring with one or more alkyl groups, alkenyl groups, or both, wherein the alkyl groups or alkenyl groups are optionally substituted.

[0096] Optional substituents for any alkyl, alkenyl and aryl group includes substitution with one or more of the following substituents, among others: halogen, including fluorine, chlorine, bromine or iodine; pseudohalides, including -ON;-COOR where R is a hydrogen or an alkyl group or an aryl group and more specifically where R is a methyl, ethyl, propyl, butyl, or phenyl group all of which groups are optionally substituted;-COR where R is a hydrogen or an alkyl group or an aryl group and more specifically where R is a methyl, ethyl, propyl, butyl, or phenyl group all of which groups are optionally substituted;-CON(R)2 where each R, independently of each other R, is a hydrogen or an alkyl group or an aryl group and more specifically where R is a methyl, ethyl, propyl, butyl, or phenyl group all of which groups are optionally substituted; and where R and R can form a ring which can contain one or more double bonds and can contain one or more additional carbon atoms;-0C0N(R)2 where each R, independently of each other R, is a hydrogen or an alkyl group or an aryl group and more specifically where R is a methyl, ethyl, propyl, butyl, or phenyl group all of which groups are optionally substituted; and where R and R can form a ring which can contain one or more double bonds and can contain one or more additional carbon atoms;-N(R)2where each R, independently of each other R, is a hydrogen, or an alkyl group, or an acyl group or an aryl group and more specifically where R is a methyl, ethyl, propyl, butyl, phenyl or acetyl group, all of which are optionally substituted; and where R and R can form a ring which can contain one or more double bonds and can contain one or more additional carbon atoms;-SR, where R is hydrogen or an alkyl group or an aryl group and more specifically where R is hydrogen, methyl, ethyl, propyl, butyl, or a phenyl group, which are optionally substituted;-SO2R, or-SOR where R is an alkyl group or an aryl group and more specifically where R is a methyl, ethyl, propyl, butyl, or phenyl group, all of which are optionally substituted;-OCOOR where R is an alkyl group or an aryl group;-SO2N(R)2where each R, independently of each other R, is a hydrogen, or an alkyl group, or an aryl group all of which are optionally substituted and wherein R and R can form a ring which can contain one or more double bonds and can contain one or more additional carbon atoms; and-OR where R is H, an alkyl group, an aryl group, or an acyl group all of which are optionally substituted. In a particular example R can be an acyl yielding -OCOR” where R” is a hydrogen or an alkyl group or an aryl group and more specifically where R” is methyl, ethyl, propyl, butyl, or phenyl groups all of which groups are optionally substituted.

[0097] Specific substituted alkyl groups include haloalkyl groups, particularly trihalomethyl groups and specifically trifluoromethyl groups. Specific substituted aryl groups include mono-, di-, tri, tetra- and pentahalo-substituted phenyl groups; mono-, di-, tri-, tetra-, penta-, hexa-, and hepta-halo-substituted naphthalene groups; 3- or 4- halo-substituted phenyl groups, 3- or 4-alkyl-substituted phenyl groups, 3- or4-alkoxy- substituted phenyl groups, 3- or 4-RCO-substituted phenyl, 5- or 6-halo-substitutednaphthalene groups. More specifically, substituted aryl groups include acetylphenyl groups, particularly 4-acetylphenyl groups; fluorophenyl groups, particularly 3- fluorophenyl and 4-fluorophenyl groups; chlorophenyl groups, particularly 3- chlorophenyl and 4-chlorophenyl groups; methylphenyl groups, particularly 4- methylphenyl groups; and methoxyphenyl groups, particularly 4-methoxyphenyl groups.

[0098] As to any of the above groups which contain one or more substituents, it is understood that such groups do not contain any substitution or substitution patterns which are sterically impractical and / or synthetically non-feasible.

[0099] Many of the molecules disclosed herein contain one or more ionizable groups. Ionizable groups include groups from which a proton can be removed (e.g.,-COOH) or added (e.g., amines) and groups that can be quaternized (e.g., amines). All possible ionic forms of such molecules and salts thereof are intended to be included individually in the disclosure herein. With regard to salts of the compounds herein, one of ordinary skill in the art can select from among a wide variety of available counterions that are appropriate for preparation of salts of this invention for a given application. In specific applications, the selection of a given anion or cation for preparation of a salt can result in increased or decreased solubility of that salt.

[0100] The compounds of this invention can contain one or more chiral centers. Accordingly, this invention is intended to include racemic mixtures, diastereomers, enantiomers, tautomers and mixtures enriched in one or more stereoisomer. The scope of the invention as described and claimed encompasses the racemic forms of the compounds as well as the individual enantiomers and non-racemic mixtures thereof.

[0101] As used herein, the term "isomers" refers to compounds having the same number and kind of atoms, and hence the same molecular weight, but differing in respect to the structural arrangement or configuration of the atoms. Isomers include, but are not limited to, structural isomers, stereoisomers, and geometric isomers. As used herein, “structural isomer” refers to a compound that has the same molecular formula as another compound but differs in the connectivity or bonding sequence of atoms.

[0102] The term "tautomer," as used herein, refers to one of two or more structural isomers which exist in equilibrium and which are readily converted from one isomeric form to another. It will be apparent to one skilled in the art that certain compounds of thisinvention may exist in tautomeric forms, all such tautomeric forms of the compounds being within the scope of the invention.

[0103] Unless otherwise stated, structures depicted herein are also meant to include all stereochemical forms of the structure; i.e., the R and S configurations for each asymmetric center. Therefore, single stereochemical isomers as well as enantiomeric and diastereomeric mixtures of the present compounds are within the scope of the invention.

[0104] Unless otherwise stated, structures depicted herein are also meant to include compounds which differ only in the presence of one or more isotopically enriched atoms. For example, compounds having the present structures except for the replacement of a hydrogen by a deuterium or tritium, or the replacement of a carbon by13C- or deenriched carbon are within the scope of this invention.

[0105] The compounds of the present invention may also contain unnatural proportions of atomic isotopes at one or more of the atoms that constitute such compounds. For example, the compounds may be radiolabeled with radioactive isotopes, such as for example tritium (3H), iodine-125 (125l), or carbon-14 (14C). All isotopic variations of the compounds of the present invention, whether radioactive or not, are encompassed within the scope of the present invention.

[0106] The symboldenotes the point of attachment of a chemical moiety, functional group, atom, ion, unpaired electron, or other chemical species to the represented molecule, compound, or chemical formula. For example, in the formula x , “X” represents a molecule or compound, the symboldenotes a point of attachment of a chemical moiety, functional group, atom, ion, unpaired electron, or other chemical species to X (where X corresponds to the represented molecule, compound, or chemical formula) via covalent bonding. As used herein, the various functional groups represented will be understood to have a point of attachment at the functional group having the hyphen or dash (-) or a dash used in combination with an asterisk (*). In other words, in the case of -CFhCF CHs or-CFhCF CHs, it will be understood that the point of attachment is the CH2 group at the far left. If a group is recited without an asterisk or a dash, then the attachment point is indicated by the plain and ordinary meaning of the recited group.

[0107] Where substituent groups are specified by their conventional chemical formulae, written from left to right, they equally encompass the chemically identical substituents that would result from writing the structure from right to left, e.g., -CH2O- is equivalent to -OCH2-.

[0108] Various potentially useful and optional descriptions, background information, applications or uses of embodiments and aspects herein, terminology (to the extent not inconsistent with the terms as defined herein), mechanisms, compositions (such as artificial melanin nanoparticles and compositions and characteristics thereof), methods, techniques, measurements, calculations, definitions, and other embodiments and aspects are found in: International Patent App. No. PCT / US2017 / 041596 (published as International Pat. Pub. No. W02018013609A2), International Patent App. No. PCT / US2020 / 039769 (published as International Pat. Pub. No. W02021021350A3), International Patent App. No. PCT / US2020 / 057902 (published as International Pat. Pub. No. W02021087076A1), International Patent App. No. PCT / US2020 / 057939 (published as International Pat. Pub. No. WO2021096692A1), International Patent App. No. PCT / US2023 / 012182 (published as International Pat. Pub. No. W02023150205A1), International Patent App. No. PCT / US2022 / 026669 (published as International Pat. Pub. No. WO2022232356A1), and International Patent App. No. PCT / US2021 / 064842 (published as International Pat. Pub. No. WO2022140532A2), each of which is incorporated herein by reference in its entirety, to the extent not inconsistent herewith.

[0109] The term “composite” or “nanocomposite” as used herein, refers to a compound or material comprising two or more distinct components. In some aspects, a composite comprises two or more distinct components where at least one component serves as a matrix material and at least one other component serves as a performance enhancing material. In embodiments, the composite exhibits improved or altered mechanical, thermal, chemical, and / or other performance characteristics due to the interaction of the components. In embodiments, the matrix material comprises a polymeric material. In embodiments, the performance enhancing material comprises an additive, such as a nanoadditive.

[0110] As used herein, the term “nanomaterial” refers to a compound or material that contains one or more components with at least one dimension on the nanoscale less than 1 pm, typically ranging from 1 to 1000 nanometers, such as 1 to 500 nanometers or 1 to 250 nanometers. The nanomaterial may be composed of particles, such asnanoparticles, fibers, tubes, or other structures. In aspects, nanomaterial refers to a material comprising two or more nanoparticles. In aspects, nanomaterial refers to a material comprising two or more melanin-like nanoparticles. In aspects, a nanomaterial may be incorporated into a matrix material, such as a polymeric material, to enhance mechanical, chemical, and / or structural properties of the matrix material.

[0111] The term "nanoparticle" as used herein, refers to a physical particle having at least one size characteristic or physical dimension less than 1 pm, typically ranging from 1 to 1000 nanometers, such as 1 to 100 nanometers. Optionally, term "nanoparticle" as used herein, refers to a physical particle whose longest size characteristic or physical dimension is less than 1 pm, typically ranging from 1 to 1000 nanometers, such as 1 to 500 nanometers or 1 to 250 nanometers.

[0112] The term, “nanoadditive” or “nanofiller” refers to a nanomaterial or a nanoparticle that may be incorporated into another material, composition, or reaction mixture to enhance or modify its properties or performance characteristics. In aspects, a nanoadditive is incorporated into another material or composition to improve properties such as mechanical strength, thermal stability, electrical conductivity, chemical reactivity, and / or other properties. In aspects, a nanoadditive is incorporated into another material or composition to improve the radiation resistance of the material or composition (e.g., by enhancing radical scavenging activity and / or improving broadband absorptive qualities). In aspects, a nanoadditive is incorporated into a reaction mixture to improve the quality of a reaction, such as by stabilizing the reaction environment or optimizing conditions to achieve more favorable or consistent results.

[0113] In the context of composites, mixtures, and / or solutions, the terms “improve”, “enhance”, and like terms refer to a measureable or perceivable (e.g., observable cracks on a surface of a material) increase or preservation in the performance of a material after it interacts, contacts, or combines with a different material in relation to a baseline. “Baseline” refers to the performance of a material before an interaction, contact, or combination with a different material. For example, contacting a polymeric material with a nanoadditive may improve or enhance the thermomechanical properties of the polymeric material by providing additional structural support, enhancing free radical scavenging activity, and / or introducing broadband absorptive qualities. For example, a protective component (e.g., a nanoparticle or nanoadditive) may disperse, adhere, or react with a matrix material component (e.g., a polymeric material), potentiallyintroducing new properties, such as improved resistance to environmental factors (e.g., radiation and / or temperature), increased conductivity, or reduced weight. In aspects, the combination of distinct materials to generate a composite synergistically enhances the overall performance of the composite beyond what either material could achieve independently. In the context of reactions, the terms “improve”, “enhance”, and like terms refer to any action or effect that results in a measurable or perceivable increase in the performance, efficiency, or outcome of the reaction. For example, an improvement in the performance of the reaction may refer to protecting a reaction from damage caused by environmental factors (e.g., radiation and / or temperature). Additionally, in some aspects, the term improve or enhance is used interchangeably with the term “maintain”, for example, to describe the preservation of a property (e.g., toughness, stability, or flexibility) under specific conditions (e.g., with and without UV exposure).

[0114] As used herein, the terms “AMNP” and “ANP” are equivalent and interchangeable and refer to artificial allomelanin nanoparticles.

[0115] As used herein, the term “SMP” refers to synthetic (or artificial) melanin particle. In some aspects and examples, an SMP is a synthetic / artificial polydopamine (PDA) particle. In some aspects and examples, an SMP is a synthetic / artificial allomelanin (ANMP or ANP) particle.

[0116] As used herein, the terms “melanin-inspired” and “melanin-like” are equivalent and interchangeable to describe certain compounds and materials disclosed herein. A melanin-inspired or melanin-like compound or material refers to a compound or material that contains one or more melanin precursors or a structural isomer thereof, such as a structural isomer of one or more melanin monomers (e.g., dopamine). For example, contacting a plurality of structural isomers of one or more melanin precursor with an oxidizing agent can result in oxidative oligomerization (or, polymerization) among the structural isomers thereby forming a melanin-inspired material.

[0117] As used herein, the terms “allomelanin-inspired” and “allomelanin-like” are equivalent and interchangeable to describe certain compounds and materials disclosed herein. Allomelanin refers to a group of melanins that consist of nitrogen-free precursors such as catechol and 1 ,8-dihydroxynaphthalene (1 ,8-DHN). An allomelanin-inspired or allomelanin-like compound or material refers to a compound or material that contains a structural isomer of one or more allomelanin precursors, such as a structural isomer ofone or more allomelanin monomers (e.g., 1 ,8-DHN). In some aspects, the structural isomer of the allomelanin precursor refers to 1 ,7-DHN or 2,3-DHN. For example, contacting a plurality of structural isomers of one or more allomelanin precursor with an oxidizing agent can result in oxidative oligomerization (or, polymerization) among the structural isomers thereby forming an allomelanin-inspired material.

[0118] In an embodiment, a composition or compound of the invention, such as an alloy or precursor to an alloy, is isolated or substantially purified. In an embodiment, an isolated or purified compound is at least partially isolated or substantially purified as would be understood in the art. In an embodiment, a substantially purified composition, compound or formulation of the invention has a chemical purity of 95%, optionally for some applications 99%, optionally for some applications 99.9%, optionally for some applications 99.99%, and optionally for some applications 99.999% pure.DETAILED DESCRIPTION OF THE INVENTION

[0119] In the following description, numerous specific details of the devices, device components and methods of the present invention are set forth in order to provide a thorough explanation of the precise nature of the invention. It will be apparent, however, to those of skill in the art that the invention can be practiced without these specific details.

[0120] Various aspects are contemplated herein, several of which are set forth in the paragraphs below. It is explicitly contemplated that any aspect or portion thereof can be combined to form an aspect. Moreover, for example, the term “any preceding aspect” means any aspect that appears prior to the aspect that contains such phrase is referenced (for example, the clause “Aspect 10: the method of any preceding aspect...” means that any aspect prior to Aspect 10 is referenced, including Aspects 1-9). In addition, it is explicitly contemplated that any reference to Aspect X, where X is an integer corresponding to one of the below Aspects (e.g., Aspect 11), includes reference to Aspects AXa, AXb, and / or AXc, if present, etc. (e.g., Aspect 11 a, Aspect 11 b, Aspect 11 c, and / or Aspect 11 d).

[0121] Aspect 1 : A nanoadditive comprising a synthetic melanin-inspired nanoparticle, wherein: the synthetic melanin-inspired nanoparticle comprises a plurality of covalently- linked artificial melanin precursors, andeach artificial melanin precursor independently comprises an artificial allomelanin precursor, an artificial eumelanin precursor, or a structural isomer thereof.

[0122] Aspect 2: The nanoadditive of aspect 1 , wherein each artificial melanin precursor independently comprises a substituted or unsubstituted catechol-based compound, a substituted or unsubstituted dihydroxynaphthalene-based compound, a substituted or unsubstituted indole-based compound, a substituted or unsubstituted dopamine-based compound, or any combination thereof.

[0123] Aspect 3: The nanoadditive of any preceding aspect, wherein each artificial melanin precursor is independently a substituted or unsubstituted dihydroxynaphthalene-based compound, or a substituted or unsubstituted dopamine- based compound.

[0124] Aspect 4: The nanoadditive of any preceding aspect, wherein each artificial melanin precursor is independently a substituted or unsubstituted: dopamine monomer, 1 ,8-dihydroxynaphthalene monomer, tyrosine monomer, tyramine monomer, catecholamine, or any combination thereof.

[0125] Aspect 5: The nanoadditive of any preceding aspect, wherein each artificial melanin precursor independently comprises substituted or unsubstituted naphthalene.

[0126] Aspect 6: The nanoadditive of any preceding aspect, wherein each artificial melanin precursor independently comprises a structural isomer of a substituted or unsubstituted 1 ,8-dihydroxynaphthalene monomer.

[0127] Aspect 7: The nanoadditive of aspect 6, or any preceding aspect, wherein the structural isomer of the substituted or unsubstituted 1 ,8-dihydroxynaphthalene monomer is a 1 ,7-dihydroxynaphthalene monomer or a 2,3-dihydroxynaphthalene monomer.

[0128] Aspect 8: The nanoadditive of aspect 6 or aspect 7, or any preceding aspect, wherein the structural isomer is more hydrophobic than the substituted or unsubstituted 1 ,8-dihydroxynaphthalene monomer.

[0129] Aspect 9: The nanoadditive of any preceding aspect, wherein each artificial melanin precursor is independently a substituted or unsubstituted 1 ,7- dihydroxynaphthalene monomer.

[0130] Aspect 10: The nanoadditive of any preceding aspect, wherein each artificial melanin precursor is independently a substituted or unsubstituted 2,3- dihydroxynaphthalene monomer.

[0131] Aspect 11 : The nanoadditive of any one of aspects 6-10, or any preceding aspect, wherein the synthetic melanin-inspired nanoparticle is characterized by a radical scavenging activity greater than that of a nanoparticle consisting of a plurality of covalently-linked 1 ,8-dihydroxynaphthalene monomers or polydopamine monomers having the same diameter as the synthetic melanin-inspired nanoparticle under otherwise identical conditions.

[0132] Aspect 12: The nanoadditive of any preceding aspect, wherein each artificial melanin precursor independently comprises a structure having the formula FX1 , FX2, FX3, or FX4:

[0133] Aspect 12a: The nanoadditive of any preceding aspect, wherein each artificial melanin precursor independently is a structure of formula FX1 , FX2, FX3, or FX4:

[0134] Aspect 12b: The nanoadditive of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle is a block copolymer or a random copolymer, and wherein each artificial melanin precursor independently comprises a structure having the formula FX2 or FX3

[0135] Aspect 12c: The nanoadditive of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle is a homopolymer, wherein each artificial melanin precursor comprises a structure having the formula FX2:

[0136] Aspect 12d: The nanoadditive of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle is a homopolymer, wherein each artificial melanin precursor comprises a structure having the formula FX3:

[0137] Aspect 13: The nanoadditive of any preceding aspect, wherein each artificial melanin precursor is free of nitrogen.

[0138] Aspect 14: The nanoadditive of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle comprises between 3 and 50 (e.g., between 3 and 50, between 3 and 40, between 3 and 30, between 5 and 50, or between 5 and 30) covalently-linked artificial melanin precursors.

[0139] Aspect 15: The nanoadditive of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle comprises between 3 and 25 (e.g., between 3 and 25 or between 3 and 20) covalently-linked artificial melanin precursors.

[0140] Aspect 16: The nanoadditive of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle comprises between 5 and 20 (e.g., 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16, 17, 18, 19, or 20) covalently-linked artificial melanin precursors.

[0141] Aspect 17: The nanoadditive of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle is hydrophobic.

[0142] Aspect 18: The nanoadditive of any preceding aspect, wherein the nanoadditive comprises between 0 wt.% and 5 wt.%, between 0 wt.% and 1 wt.%, between 0 wt.% and 0.5 wt.%, preferably between 0 wt.% and 0.25%, more preferably between 0 wt.% and 0.1 wt.%, of non-covalently-linked artificial melanin precursors or monomers based on the total weight of the nanoadditive.

[0143] Aspect 19: The nanoadditive of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle has a shape characterized by a sphere having a diameter selected from the range of 100 nm to 300 nm (e.g., 100 nm to 300 nm, 150 nm to 300 nm, 100 nm to 200 nm, or 150 nm to 200 nm).

[0144] Aspect 19a: The nanoadditive of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle has a size (or, characteristic size, such as diameter) selected from the range of 100 nm to 300 nm (e.g., 100 nm to 300 nm, 150 nm to 300 nm, 100 nm to 200 nm, or 150 nm to 200 nm).

[0145] Aspect 19b: The nanoadditive of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle forms a mixture of aggregates having a size (or, characteristic size, such as diameter) selected from the range of 200 nm to 2000 nm (e.g., 200 nm to 2000 nm, 200 nm to 1500 nm, 250 nm to 2000 nm, or 250 nm to 1500 nm).

[0146] Aspect 20: The nanoadditive of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle is a porous synthetic melanin-inspired nanoparticle.

[0147] Aspect 21 : The nanoadditive of any preceding aspect being dispersed in a solvent or solvent mixture, thereby forming a nanoadditive dispersion.

[0148] Aspect 22: The nanoadditive of aspect 21 , or any preceding aspect, wherein the solvent or solvent mixture is at least 50% water (optionally at least 50%, optionally at least 60%, optionally at least 70%, optionally at least 80%, optionally at least 90%, or optionally at least 95% water).

[0149] Aspect 23: The nanoadditive of aspect 21 or 22, or any preceding aspect, wherein the synthetic melanin-inspired nanoparticle in the nanoadditive dispersion is characterized by a zeta potential, or an average zeta potential, selected from the range of -50 mV to -10 mV (e.g., -50 mV to -10 mV, -40 mV to -10 mV, or -40 mV to -20 mV).

[0150] Aspect 23a: The nanoadditive of aspect 23, or any preceding aspect, wherein the synthetic melanin-inspired nanoparticle in the nanoadditive dispersion is characterized by a zeta potential, or an average zeta potential, of about -33 mV.

[0151] Aspect 23b: The nanoadditive of aspect 23, or any preceding aspect, wherein the synthetic melanin-inspired nanoparticle in the nanoadditive dispersion is characterized by a zeta potential, or an average zeta potential, of about -35 mV.

[0152] Aspect 24: The nanoadditive of aspect 21 , or any preceding aspect, wherein the solvent or solvent mixture is an inorganic solvent or inorganic solvent mixture and the synthetic melanin-inspired nanoparticle is miscible in the inorganic solvent or inorganic solvent mixture.

[0153] Aspect 24a: The nanoadditive of aspect 24, or any preceding aspect, wherein the inorganic solvent is, or the inorganic solvent mixture comprises, ethyl acetate, acetone, methyl acetate, isopropyl acetate, diethyl ether, tetrahydrofuran, dichloromethane, ethanol, or any combination thereof.

[0154] Aspect 25: The nanoadditive of any preceding aspect, wherein the nanoadditive is non-toxic, biocompatible, degradable, or any combination thereof.

[0155] Aspect 26: The nanoadditive of any preceding aspect, wherein the nanoadditive is characterized by a green pigmentation, a black pigmentation, a pink pigmentation, or a tan pigmentation.

[0156] Aspect 26a: The nanoadditive of any preceding aspect, wherein the nanoadditive is characterized by a green pigmentation, a black pigmentation, or a green-black pigmentation.

[0157] Aspect 26b: The nanoadditive of any preceding aspect, wherein the nanoadditive is characterized by a pink pigmentation, a tan pigmentation, or a pink-tan pigmentation.

[0158] Aspect 27: A polymer nanocomposite comprising: the nanoadditive of any preceding aspect; and a polymeric material.

[0159] Aspect 28: A polymer nanocomposite comprising: a nanoadditive, wherein the nanoadditive comprises: a synthetic melanin-inspired nanoparticle comprising a plurality of covalently-linked artificial melanin precursors, wherein each artificial melanin precursor independently comprises an artificial allomelanin precursor, an artificial eumelanin precursor, or a structural isomer thereof; and a polymeric material.

[0160] Aspect 29: The polymer nanocomposite of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle is present in the polymer nanocomposite in an amount of between 0.01 wt.% and 10 wt.%, optionally between 0.05 wt.% and 10 wt.%, optionally between 0.05 wt.% and 7.5 wt.%, optionally between 0.05 wt.% and 5 wt.%, optionally between 0.05 wt.% and 2.5 wt.%, optionally between 0.05 wt.% and 2 wt.%, optionally between 0.05 wt.% and 1 .5 wt.%, optionally between 0.1 wt.% and 10 wt.%, optionally between 0.1 wt.% and 7.5 wt.%, optionally between 0.1 wt.% and 5 wt.%, optionally between 0.1 wt.% and 2.5 wt.%, optionally between 0.1 wt.% and 2 wt.%, optionally between 0.1 wt.% and 1.5 wt.%, or optionally between 0.1 wt.% to 1 wt.% based on the total weight of the polymer nanocomposite.

[0161] Aspect 29a: The polymer nanocomposite of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle is present in the polymer nanocomposite in an amount of between 0.1 wt.% and 1 wt.% (e.g., 0.1 wt.%, 0.25 wt.%, 0.5 wt.%, 0.75 wt.%, or 1 wt.%) based on the total weight of the polymer nanocomposite.

[0162] Aspect 30: The polymer nanocomposite of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle is present in the polymer nanocomposite in an amount of between 0.25 wt.% to 0.5 wt.% based on the total weight of the polymer nanocomposite.

[0163] Aspect 31 : The polymer nanocomposite of any preceding aspect, wherein the polymer nanocomposite is characterized by at least one mechanical property that is enhanced (e.g., enhanced, improved, or maintained) as compared to a baseline mechanical property of the polymeric material without the nanoadditive.

[0164] Aspect 32: The polymer nanocomposite of aspect 31 , or any preceding aspect, wherein the at least one mechanical property comprises: (i) ultimate tensile strength; (ii) elongation; (iii) toughness; (iv) elasticity; (v) resistance to crack formation; (vi) preservation of the polymer nanocomposite surface chemistry; (vii) radiation resistance; (viii) broadband absorption; (ix) radical scavenging behavior; (x) light energy quenching; or (xi) any combination thereof.

[0165] Aspect 33: The polymer nanocomposite of aspect 32, or any preceding aspect, wherein the radiation resistance comprises resistance to UV radiation, gamma ray radiation, and / or x-ray radiation.

[0166] Aspect 34: The polymer nanocomposite of any preceding aspect, wherein the polymeric material comprises a plurality of cross-linked polymers.

[0167] Aspect 35: The polymer nanocomposite of any preceding aspect, wherein the polymeric material comprises a block copolymer.

[0168] Aspect 36: The polymer nanocomposite of any preceding aspect, wherein the polymeric material comprises an elastomer, a resin, or a silicone.

[0169] Aspect 37: The polymer nanocomposite of any preceding aspect, wherein the polymeric material comprises polyurethane, polyolefins, polyesters, polyamides, polycarbonates, polysiloxanes, or a blend thereof.

[0170] Aspect 38: The polymer nanocomposite of any preceding aspect, wherein the polymeric material comprises a thermoplastic polymer or a thermosetting polymer.

[0171] Aspect 39: The polymer nanocomposite of any preceding aspect, wherein the polymeric material is selected from the group consisting of epoxy resins, silicone elastomers, bismaleimide resins, cyanate ester resins, and epoxy-amine thermosets.

[0172] Aspect 40: The polymer nanocomposite of any preceding aspect, wherein the polymeric material comprises polyurethane.

[0173] Aspect 41 : The polymer nanocomposite of any preceding aspect, wherein the polymeric material is or comprises a polyurethane elastomer or a polyurethane resin.

[0174] Aspect 41 a: The polymer nanocomposite of any preceding aspect, wherein the polymeric material is a polyurethane elastomer or a polyurethane resin.

[0175] Aspect 42: The polymer nanocomposite of any preceding aspect, wherein each artificial melanin precursor independently comprises a structure having the formula FX1 , FX2, FX3, or FX4:

[0176] Aspect 42a: The polymer nanocomposite of any preceding aspect, wherein each artificial melanin precursor independently is a structure of formula FX1 , FX2, FX3, or FX4:

[0177] Aspect 42b: The polymer nanocomposite of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle is a block copolymer or a random copolymer, and wherein each artificial melanin precursor independently comprises a structure having the formula FX2 or FX3:

[0178] Aspect 42c: The polymer nanocomposite of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle is a homopolymer, wherein each artificial melanin precursor comprises a structure having the formula FX2:

[0179] Aspect 42d: The polymer nanocomposite of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle is a homopolymer, wherein each artificial melanin precursor comprises a structure having the formula FX3:

[0180] Aspect 43: A method of protecting a polymeric material from ionizing radiation, the method comprising incorporating the nanoadditive of any preceding aspect into the polymeric material.

[0181] Aspect 44: A radiation protective nanoadditive for a polyurethane nanocomposite comprising the nanoadditive or the synthetic melanin-inspired nanoparticle of any preceding aspect.

[0182] Aspect 45: A method of generating a polymer nanocomposite, the method comprising: providing a plurality of artificial melanin monomers comprising artificial allomelanin precursors, artificial eumelanin precursors, and / or structural isomers thereof; polymerizing the plurality of artificial melanin monomers to form a synthetic melanin-inspired nanoparticle; and contacting at least a portion of a polymeric material with the synthetic melanin- inspired nanoparticle to generate a polymer nanocomposite; wherein the synthetic melanin-inspired nanoparticle is present in the polymer nanocomposite in an amount of between 0.01 wt.% and 10 wt.%, optionally between 0.05 wt.% and 10 wt.%, optionally between 0.05 wt.% and 7.5 wt.%, optionally between 0.05 wt.% and 5 wt.%, optionally between 0.05 wt.% and 2.5 wt.%, optionally between 0.05 wt.% and 2 wt.%, optionally between 0.05 wt.% and 1 .5 wt.%, optionally between 0.1 wt.% and 10 wt.%, optionally between 0.1 wt.% and 7.5 wt.%, optionally between 0.1 wt.% and 5 wt.%, optionally between 0.1 wt.% and 2.5 wt.%, optionally between 0.1 wt.% and 2 wt.%, optionally between 0.1 wt.% and 1 .5 wt.%, or optionally between 0.1 wt.% to 1 wt.% based on the total weight of the polymer nanocomposite; thereby generating a polymer nanocomposite.

[0183] Aspect 45a: A method of generating a polymer nanocomposite, the method comprising: providing a plurality of artificial melanin monomers comprising artificial allomelanin precursors, artificial eumelanin precursors, and / or structural isomers thereof; polymerizing the plurality of artificial melanin monomers to form a synthetic melanin-inspired nanoparticle; and contacting at least a portion of a polymeric material with the synthetic melanin- inspired nanoparticle to generate a polymer nanocomposite; wherein the synthetic melanin-inspired nanoparticle is present in the polymer nanocomposite in an amount of between 0.1 wt.% and 1 wt.% (e.g., 0.1 wt.%, 0.25 wt.%, 0.5 wt.%, 0.75 wt.%, or 1 wt.%) based on the total weight of the polymer nanocomposite; thereby generating a polymer nanocomposite.

[0184] Aspect 46: The method of aspect 45, or any preceding aspect, wherein the contacting step comprises: contacting a first subcomponent of the polymeric material with the synthetic melanin-inspired nanoparticle to generate a nanoparticle-containing subcomponent; and combining the nanoparticle-containing subcomponent with a second subcomponent of the polymeric material to generate the polymer nanocomposite.

[0185] Aspect 47: The method of aspect 45 or 46, or any preceding aspect, wherein the polymerizing step comprises oxidative oligomerization or polymerization.

[0186] Aspect 48: The method of any one of aspects 45-47, or any preceding aspect, further comprising lyophilizing the synthetic melanin-inspired nanoparticle prior to the contacting step to generate a lyophilized synthetic melanin-inspired nanoparticle.

[0187] Aspect 49: The method of any one of aspects 45-48, or any preceding aspect, wherein the polymeric material comprises an elastomer, a resin, or a silicone.

[0188] Aspect 50: The method of any one of aspects 45-49, or any preceding aspect, wherein the polymeric material comprises polyurethane, polyolefins, polyesters, polyamides, polycarbonates, polysiloxanes, or a blend thereof.

[0189] Aspect 51 : The method of any one of aspects 45-50, or any preceding aspect, wherein the polymeric material comprises a thermoplastic polymer or a thermosetting polymer.

[0190] Aspect 52: The method of any one of aspects 45-51 , or any preceding aspect, wherein the polymeric material is selected from the group consisting of epoxy resins, silicone elastomers, bismaleimide resins, cyanate ester resins, and epoxy-amine thermosets.

[0191] Aspect 53: The method of any one of aspects 46-52, or any preceding aspect, wherein the polymeric material comprises polyurethane, and the first subcomponent of the polymeric material comprises isocyanate.

[0192] Aspect 54: The method of aspect 53, or any preceding aspect, wherein the second subcomponent of the polymeric material comprises polyols.

[0193] Aspect 55: The method of any one of aspects 45-54, or any preceding aspect, wherein the contacting step does not comprise an organic solvent, a surfactant, or an additional additive.

[0194] Aspect 55a: The method of any one of aspects 45-54, or any preceding aspect, wherein the contacting step does not comprise an organic solvent.

[0195] Aspect 55b: The method of any one of aspects 45-54, or any preceding aspect, wherein the contacting step does not comprise an organic solvent or a surfactant.

[0196] Aspect 56: The method of any one of aspects 45-55, or any preceding aspect, wherein each artificial melanin precursor independently comprises a structure having the formula FX1 , FX2, FX3, or FX4:

[0197] Aspect 56a: The method of any preceding aspect, wherein each artificial melanin precursor independently is a structure of formula FX1 , FX2, FX3, or FX4:

[0198] Aspect 56b: The method of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle is a block copolymer or a random copolymer, and wherein each artificial melanin precursor independently comprises a structure having the formula FX2 or FX3

[0199] Aspect 56c: The method of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle is a homopolymer, wherein each artificial melanin precursor comprises a structure having the formula FX2:

[0200] Aspect 56d: The method of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle is a homopolymer, wherein each artificial melanin precursor comprises a structure having the formula FX3:

[0201] Aspect 57: A method of enhancing a mechanical property of a polymeric material, the method comprising: providing a plurality of artificial melanin monomers comprising a substituted or unsubstituted 1 ,8-dihydroxynaphthalene monomer or a structural isomer thereof; polymerizing the plurality of artificial melanin monomers to form a synthetic melanin-inspired nanoparticle; and contacting at least a portion of a polymeric material with the synthetic melanin- inspired nanoparticle to generate a polymer nanocomposite characterized by at least one enhanced mechanical property; wherein the synthetic melanin-inspired nanoparticle is present in the polymer nanocomposite in an amount of between 0.01 wt.% and 10 wt.%, optionally between 0.05 wt.% and 10 wt.%, optionally between 0.05 wt.% and 7.5 wt.%, optionally between 0.05 wt.% and 5 wt.%, optionally between 0.05 wt.% and 2.5 wt.%, optionally between 0.05 wt.% and 2 wt.%, optionally between 0.05 wt.% and 1 .5 wt.%, optionally between 0.1 wt.% and 10 wt.%, optionally between 0.1 wt.% and 7.5 wt.%, optionallybetween 0.1 wt.% and 5 wt.%, optionally between 0.1 wt.% and 2.5 wt.%, optionally between 0.1 wt.% and 2 wt.%, optionally between 0.1 wt.% and 1 .5 wt.%, or optionally between 0.1 wt.% to 1 wt.% based on the total weight of the polymer nanocomposite; thereby enhancing a mechanical property of a polymeric material.

[0202] Aspect 57a: A method of enhancing a mechanical property of a polymeric material, the method comprising: providing a plurality of artificial melanin monomers comprising a substituted or unsubstituted 1 ,8-dihydroxynaphthalene monomer or a structural isomer thereof; polymerizing the plurality of artificial melanin monomers to form a synthetic melanin-inspired nanoparticle; and contacting at least a portion of a polymeric material with the synthetic melanin- inspired nanoparticle to generate a polymer nanocomposite characterized by at least one enhanced mechanical property; wherein the synthetic melanin-inspired nanoparticle is present in the polymer nanocomposite in an amount of between 0.1 wt.% and 1 wt.% (e.g., 0.1 wt.%, 0.25 wt.%, 0.5 wt.%, 0.75 wt.%, or 1 wt.%) based on the total weight of the polymer nanocomposite; thereby enhancing a mechanical property of a polymeric material.

[0203] Aspect 58: The method of aspect 57, or any preceding aspect, wherein the contacting step comprises: contacting a first subcomponent of the polymeric material with the synthetic melanin-inspired nanoparticle to generate a nanoparticle-containing subcomponent; and combining the nanoparticle-containing subcomponent with a second subcomponent of the polymeric material to generate the polymer nanocomposite characterized by at least one enhanced mechanical property.

[0204] Aspect 59: The method of aspect 58, or any preceding aspect, wherein the polymeric material comprises polyurethane, the first subcomponent of the polymericmaterial comprises isocyanates, and the second subcomponent of the polymeric material comprises polyols.

[0205] Aspect 60: The method of any one of aspects 57-59, or any preceding aspect, wherein the at least one enhanced mechanical property comprises: (i) ultimate tensile strength; (ii) elongation; (iii) toughness; (iv) elasticity; (v) resistance to crack formation;(vi) preservation of the polymer nanocomposite surface chemistry; (vii) radiation resistance; (viii) broadband absorption; (ix) radical scavenging behavior; (x) light energy quenching; or (xi) any combination thereof.

[0206] Aspect 61 : The method of any one of aspects 57-60, or any preceding aspect, wherein each artificial melanin monomer independently comprises a structure having the formula FX1 , FX2, or FX3:

[0207] Aspect 61a: The method of any preceding aspect, wherein each artificial melanin monomer independently is a structure of formula FX1 , FX2, or FX3:

[0208] Aspect 61 b: The method of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle is a block copolymer or a random copolymer, and wherein each artificial melanin monomer independently comprises a structure having the formula FX2 or FX3:

[0209] Aspect 61c: The method of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle is a homopolymer, wherein each artificial melanin monomer comprises a structure having the formula FX2:

[0210] Aspect 61 d: The method of any preceding aspect, wherein the synthetic melanin-inspired nanoparticle is a homopolymer, wherein each artificial melanin monomer comprises a structure having the formula FX3:

[0211] The invention can be further understood by the following non-limiting examples.

[0212] EXAMPLES

[0213] The following Examples comprise some exemplary but not limiting methods, materials, processes, techniques, compositions, formulations, etc., useful in the practice of the invention as well as exemplary but not limiting data, discussion, and hypotheses,without wishing to be bound by any particular theory. It is recognized that regardless of the ultimate correctness of any mechanistic explanation or hypothesis, an embodiment of the invention can nonetheless be operative and useful.

[0214] Example 1A - Synthesis and Characterization of Eumelanin and Allomelanin Nanoparticle.

[0215] Allomelanin is a lesser studied type of melanin compared to polydopamine derivatives which is nitrogen-free and found primarily in plants and fungi. Here, it was hypothesized that the over expression of allomelanin could be used to protect against the high exposure to ionizing radiation.26-31While attempts to isolate allomelanin from natural samples have been previously published on, its highly adhesive properties make it difficult to separate from covalently bound aliphatic molecules.32Thus, we sought to develop synthetic analogues of allomelanin with the same favorable properties of natural melanin but without any impurities.

[0216] The oxidative polymerization of 1 ,8 dihydroxynapthalene (1 ,8DHN) has been reported to yield well-defined spherical synthetic allomelanin nanoparticles that exhibit radical scavenging, UV-protective properties, and high surface area3334Thus, synthetic allomelanin nanoparticles derivatives as well as eumelanin were selected as candidate nanofillers for Pll elastomer nanocomposites to investigate their structural support properties and radiation protection of polymeric material.

[0217] Synthetic eumelanin and allomelanin were oxidatively polymerized from dopamine and 1 ,8DHN to yield well-defined spherical nanoparticles, polydopamine (PDA) (FIG. 6A) and poly-1 ,8DHN (p-1 ,8DHN) (FIG. 7A), respectively. A commercial PU elastomer kit (Smooth-On VytaFlex20) was used and is composed of a part A mixture of polyols and a part B component of isocyanates. A general PU synthesis scheme with polyol and isocyanate is depicted in FIG. 18. To incorporate the synthetic PDA and p- 1 ,8DHN melanin nanoparticles into the PU elastomer, the particles were lyophilized, added to the less viscous part B component, and sonicated for 1.5 hours. Then, part A and part B components were centrifugally mixed in a 1 :1 mass ratio, cured at room temperature for 16 hours, then heat cured in the oven for 8 hours at 65 °C, yielding PDA-PU and p-1 ,8DHN-PU composites (FIGs. 6B & 7B, respectively).

[0218] These composites, however, had poor tensile mechanical properties in comparison to the neat PU control, as shown in FIGs. 6C & 6D for PDA-PU compositesand FIGs. 7C & 7D for p-1 ,8DHN-PU composites. This is likely due to poor dispersion of the nanoparticles and poor interfacial interactions between the hydrophilic nanoparticles and the relatively hydrophobic PU resin. Thus, to address the low compatibility of the PDA-NPs and p-1 ,8DHN with the PU, alternative allomelanin-inspired materials were pursued.

[0219] Example 1B - Synthesis and Characterization of Allomelanin-Like Nanomaterials.

[0220] The 1 ,8DHN monomer precursor to allomelanin has a variety of structural isomers that can also be oxidatively polymerized to form allomelanin-like nanomaterials. However, unlike PDA and synthetic allomelanin precursors, polymerization of DHN isomers and their resulting melanin-like nanomaterials has not been sufficiently characterized in the literature in the context of radiation protection in polymeric materials. Thus, we sought to investigate the properties of certain 1 ,8DHN monomer precursors to evaluate their potential for protecting polymeric materials.

[0221] Through a solvent partitioning screening procedure, 1 ,7DHN and 2,3DHN monomers were selected and oxidatively polymerized to form poly-1 ,7DHN (p-1 ,7DHN) (FIG. 1A) and poly-2, 3DHN (p-2,3DHN) (FIG. 1B), respectively. In water, p-1 ,7DHN formed well-defined spherical nanoparticles around -170 nm in diameter, while p- 2,3DHN formed a mixture of aggregates around -300 nm in diameter and larger aggregates > 1000 nm (Table 1).Table 1. Size and zeta potential of p-1,7DHN, p-2,3DHN, PDA, and p-1,8DHN.

[0222] Notably, the p-1 ,7DHN exhibited a dark green-black color while the p-2,3DHN exhibited a lighter-colored, pink, tan pigmentation. The pigmentation of p-2,3DHN was unexpected. This color is not typical of melanin and melanin-like materials, which are typically dark black / brown pigments. The simultaneous efficient dispersion of p-2,3DHN and light pigmentation is believed to enable the resulting composite to have tunable transparency, as shown in FIGs. 2D and 2E and as discussed in more detail below.

[0223] Matrix assisted laser desorption / ionization coupled with time-of-f light mass spectrometry (MALDI-TOF) spectra show that p-1 ,7DHN (FIG. 1C, top) and p-2,3DHN (FIG. 1C, bottom) are made up of self-assembled oligomers of up to 18- and 14-mers, respectively. Within the MALDI, the distance between each of the respective peaks in both p-1 ,7DHN and p-2,3DHN are around 158-160 Da, which corresponds to an “inchain” DHN unit that has been previously observed in the literature for the p-1 ,8DHN.33Fourier Transform Infrared (FT-IR) spectroscopy confirmed the polymerization of the 1.7DHN and 2,3DHN monomers indicated by broadening of peaks in between 1000- 1500 cm-1and shift in -OH peak from -3300 cm-1to -3500 cm-1(FIG. 1D).

[0224] UV-Vis spectra showed that both the p-1 ,7DHN and p-2,3DHN nanoparticles are broadband absorbers, which is characteristic of melanin-like materials (FIG. 1E). This broadband absorptive quality enables melanin to protect against UV-light through the photothermal effect in which light is absorbed and converted non-radiatively to heat.35A standard 1 , 1 -diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay also showed that p-1 ,7DHN and p-2,3 DHN both have exceptional radical scavenging behavior, significantly outperforming p-1 ,8DHN, the canonical synthetic allomelanin analogue (FIG. 1F). We hypothesized that the broadband absorption and enhanced radical scavenging behavior of p-1 ,7DHN and p-2,3DHN nanomaterials would make them useful as ionizing radiation protectants. Another characteristic feature of melanin is its aromaticity and intrinsic radical content, which also plays a role in photoprotection by dissipating and trapping recoil electrons generated by Compton scattering of incident radiation.3637Electron paramagnetic resonance (EPR) spectra tests of the p-1 ,7DHN and p-2,3DHN were conducted. EPR spectra of 4-hydroxy TEMPO at 5, 10, 100, and 500 pM in water is shown in FIG. 8A. Radical content of p-1 ,7DHN and p-2,3DHN was determined using the 4-hydroxy TEMPO calibration curve depicted in FIG. 8B and expressed in units pmol of radical per mg of DHN-nanoparticles. EPR spectra of p- 1 ,7DHN showed that these materials have an intrinsic stable radical content, however p-2.3DHN does not (compare results depicted in FIG. 8C (p-1 ,7DHN) with FIG. 8D (p- 2.3DHN)). While p-2,3DHN seems to have very little intrinsic radical content, it still has the highest radical scavenging activity, which may be attributed to the lesser degree of intermolecular crosslinking upon self-assembly that allows for better accessibility between redox active functional groups and free radicals. Nevertheless, we hypothesized that both p-1 ,7DHN and p-2,3DHN would facilitate radiation protection and provide an avenue for tunability in pigment of the resulting composite.

[0225] Example 2A - Evaluation of Mechanical Properties of Polyurethane Composites; Hydrophobicity.

[0226] Beyond its broadband absorption and radical scavenging properties, these p- 1 ,7DHN and p-2,3DHN were specifically selected based off their interesting solvent partitioning into ethyl acetate over water in contrast to p-1 ,8DHN and PDA. (FIG. 9). While the more hydrophilic PDA-NPs and p-1 ,8DHN selectively partitioned into the water layer, p-1 ,7DHN partially partitioned into the ethyl acetate and water layer while the p-2,3DHN entirely partitioned into the ethyl acetate layer. This partitioning into ethyl acetate is likely due to the increased hydrophobicity of these nanoparticles, which we hypothesized would enhance their incorporation into the Pll elastomer resin.

[0227] To test our hypothesis, the p-1 ,7DHN and p-2,3DHN were added in various weight percents into a commercial Pll resin kit in the same fashion as the p-1 ,8DHN and PDA composites (see, Example 1A, above). Optically, the p-1 ,7DHN seemed to incorporate well into the PU at all observed weight percents (wt%) (FIG. 2A), but as expected, lacked optical transparency particularly in the visible wavelengths due to its dark pigmentation as seen in the UVA / is / NIR transmission spectra (FIG. 2B). The p- 2.3DHN also optically incorporated well into the PU matrix at all observed weight percents (wt%). In contrast to p-1 ,7DHN, incorporation of p-2,3DHN into the PU maintained optical transparency as shown in the images (FIG. 2D) and in the UV- Vis / NIR transmission spectra (FIG. 2E).

[0228] Example 2B - Evaluation of Mechanical Properties of Polyurethane Composites; Tensile Mechanical Properties.

[0229] To test the effect of adding the p-1 ,7DHN on the mechanical properties, tensile testing was performed on the composites (results depicted in Table 2). The neat PU achieved a toughness of 2.43 MJ / m3(FIG. 2C), which corresponds well with valuespreviously reported in the literature.14The addition of p-1 ,7DHN to the composites led to an enhancement in the resulting toughness of the elastomer, with the stress-strain curve showing an inverse relationship between the weight percent of p-1 ,7DHN added and the resulting toughness (FIG. 2C). Adding p-2,3DHN also showed an inverse relationship between wt% of p-2,3DHN added and the resulting toughness (FIG. 2F). This inverse relationship between wt% of nanoparticles added and the resulting toughness is likely attributed to the aggregation of the p-1 ,7DHN and p-2,3DHN within the PU at higher wt%, leading to premature failure of these composites. In both the p-1 ,7DHN-PU and p- 2,3DHN-PU composites, the enhancement in ultimate tensile strength (UTS) and extensibility at such low wt% is likely due to the covalent bonding between the particles and the matrix, which can not only improve the strength of the material, but also facilitate crack blunting effects rather than solely delamination from the matrix.38The 0.1wt% p-1 ,7DHN-PU and 0.25wt% p-2,3DHN-PU composites demonstrated the highest toughness at 3.80 ± 0.47and 4.49 ± 0.63 MJ / m3, respectively. Notably, the 0.25wt% and 0.5wt% p-1 ,7DHN-PU composites as well as 0.5wt% p-2,3DHN-PU composite also outperformed the tensile mechanical properties of the neat PU material (Table 2)

[0230] Indeed, the interesting and unexpected partitioning of p-1 ,7DHN and p- 2.3DNH into organic solvents, as compared to PDA and p-1 ,8DHN (FIG. 9), is believed to contribute to the enhanced incorporation into the hydrophobic matrix of PU. This better incorporation and dispersion of these nanomaterials into the PU matrix contributes to the maintained or enhanced tensile mechanical properties and uniform protection of the composite upon radiation application. The PDA and p-1 ,8DHN were not able to incorporate as well into the composite, leading to aggregation within the PU and decrease in tensile mechanical properties (see, e.g., FIGs. 6A-6D & FIGs. 7A-7D).Table 2. Tensile mechanical properties of all UVB irradiated and non-irradiated PU composites.

[0231] To confirm the importance of DHN monomer polymerization and selfassembly into nanoparticles for the enhancement in the PU mechanical properties, the 1 ,7DHN and 2,3DHN monomers were copolymerized into the PU composite. These hydrophobic monomers incorporated quite readily into the resin forming an optically transparent material (FIG. 10A showing (i) 0.25wt% 1 ,7DHN-PU composite (ii) 0.25wt% 2.3DHN-PU composite). Despite facile incorporation, addition of the monomer into the PU lead to significant embrittlement of the composite as shown in the representative stress-strain curves (FIG. 10B showing stress-strain curves for (i) 0.25wt% 1 ,7DHN-PU composite (ii) 0.25wt% 2.3DHN-PU composite as compared to the control of 0wt% DHN monomers) and UTS, elongation at failure and toughness values of the same (FIG. 10C). These results demonstrate the importance of the polymerization and selfassembly of the p-1 ,7DHN and p-2,3DHN nanomaterials for the enhancement of mechanical properties.

[0232] Example 2C - Evaluation of Mechanical Properties of Polyurethane Composites; UVB Radiation Resistance.

[0233] To test the resistance of these Pll composites from radiation, these composites and the neat Pll elastomers were irradiated with a UVB light (15 W, 312 nm, 30h). The tensile mechanical properties of the p-1 ,7DHN-PU and p-2,3DHN-PUcomposites were measured pre- and post-irradiation. The neat Pll showed a significant, 60% decrease in tensile properties post-irradiation, going from a toughness of 2.43 ± 0.09 to 0.96 ± 0.18 MJ / m3(FIG. 3A). Of all the composites, the 0.25wt% p-1 .7DHN-PU and 0.25wt% p-2,3DHN-PU performed the best, showing both high initial tensile mechanical properties while maintaining those properties the best both pre- and post- UVB irradiation (FIG. 3B (0.25wt% p-1 ,7DHN-PU), & FIG. 3C (0.25wt% p-2,3DHN-PU)). While the neat Pll elastomers upon irradiation underwent a significant decrease in UTS, elongation, and toughness, both 0.25wt% p-1 ,7DHN-PU and 0.25wt% p-2,3DHN-PU showed only slight changes in UTS, elongation and toughness post-irradiation (FIGs. 3D, 3E, & 3F, respectively). For instance, the 0.25wt% p-1 ,7DHN-PU composite underwent a 12% decrease in toughness from 3.73 ± 0.37 to 3.28 ± 0.31 MJ / m3’ and the 0.25wt% p-2,3DHN-PU composite underwent a 7% decrease in toughness from 4.49 ± 0.63 to 4.18 ± 0.15 MJ / m.3Moreover, both 0.25wt% p-1 ,7DHN-PU and 0.25wt% p- 2.3DHN-PU showed only slight changes in Young’s Modulus (MPa) post-irradiation, as shown in FIG. 3G.

[0234] Notably, while the 0.1wt% p-1 ,7DHN-PU composite achieved a higher toughness than the 0.25wt% p-1 ,7DHN-PU pre-irradiation, after UVB irradiation was applied the 0.1wt% p-1 ,7DHN-PU composite showed a significant decrease in mechanical properties (FIGs. 11A-11 E, FIGs. 13A-13C, Table 2). This showed that 0.1 wt% was likely too low of loading for the p-1 ,7DHN to effectively protect the composite from irradiation. This phenomenon was strictly seen only with the 0.1wt% p- 1.7DHN-PU composite as all other observed composites showed maintained tensile mechanical properties post-irradiation (FIGs. 11A-11 E, FIGs. 13A-13C, Table 2). Additionally, the p-2,3DHN-PU composites showed maintained tensile mechanical properties post-UVB irradiation at all observed wt% (FIGs. 12A-12E).

[0235] Example 2D - Evaluation of Mechanical Properties of Polyurethane Composites; Gamma Radiation Resistance.

[0236] To test the resistance of these PU composites, 0.25wt% and 0.5wt% of p- 1.7DHN-PU and p-2,3DHN-PU were irradiated with 5, 10, 15, and 20 kGy of gamma irradiation and their tensile mechanical properties were characterized. They were also compared against irradiated neat PU. In this example, the radiation source was Cobalt- 60 with a dose rate of 109 Gy / min. Tensile stress strain curves were measured pre- and post- gamma irradiation at the four dosages (FIG. 16A (5 kGy), FIG. 16B (10 kGy), FIG.16C (15 kGy) and FIG. 16D (20 kGy) and the tensile mechanical properties were analyzed (FIG. 17 A (ultimate tensile strength), FIG. 17B (elongation at failure), FIG.17C (toughness), and Table 3).Table 3. Tensile mechanical properties of pre- and post-Gamma irradiated PU composites.

[0237] To better understand the effects of gamma irradiation on the composites, the toughness can be further analyzed as its value is the area under the stress-strain curve and thus, directly determined by the UTS and elongation. A paired t-test statistical analysis was applied and coded in Python using SciPy. stats package to determine the statistical significance of these differences in the toughness values pre- and postgamma irradiation. Statistical significance was defined as follows: n.s. P > 0.05, *P < 0.05. At 5kGy, only the neat PU (0 wt%) showed significant changes to the toughness, while all other p-1 ,7DHN-PU and p-2,3DHN-PU composites showed non-significant changes. At 10kGy, the neat PU and 0.25wt% p-1 ,7DHN-PU composite showed significant changes upon irradiation while all other composites showed non-significant changes. At 15 kGy dosage, the neat PU, 0.5wt% p-1 ,7DHN-PU composite, and 0.25wt% p-2,3DHN-PU composite showed significant changes upon irradiation while all other composites showed non-significant changes. Finally, at 20 kGy dosages, the 0.25wt% p-1 ,7DHN-PU, 0.25wt% p-2,3DHN-PU, and neat PU showed significant changes to the toughness while 0.5wt% p-1 ,7DHN-PU and 0.5wt% p-2,3DHN-PU still showed non-significant changes. Observation of the results at the lowest (5kGy) and highest (20kGy) doses, it’s evident that the damaging effect of the radiation has a greater impact on the composites with lower weight percent (0.25wt%) of the allomelanin-like nanofiller (p-1 ,7DHN and p-2,3DHN) than the higher weight percent (0.5wt%). Thus, the addition of a higher weight percent of the allomelanin-filler enables better protection against gamma irradiation at higher doses.

[0238] While this trend remains consistent within the p-2,3DHN-PU composites, there does seem to be some slight inconsistencies in this trend specifically in the 10kGy and 15kGy dosages, specifically of the p-1 ,7DHN-PU composites. For instance, the 0.25wt% p-1 .7DHN-PU composite shows significant differences in toughness at the lower 10 kGy, but non-significant differences at the higher 15kGy dose. Another instance of this is the 0.5wt% p-1 ,7DHN-PU shows significant differences in toughness at 15kGy but shows non-significant differences at the higher 20kGy doses. For this case, while the t-test shows significant differences at 15kGy, the relative percent change pre- and post-radiation is still quite low at around a -9% decrease. Both of these inconsistencies may be a result of a greater lack of uniformity in the distribution of p- 1.7DHN within these composites leading to uneven protection against gamma radiation that leads to these inconsistencies in the trend. It is also possible that there is a morenuanced interaction between the p-1 ,7DHN and PU upon exposure to the gamma radiation that may influence the resulting toughness.

[0239] Example 2E - Evaluation of Mechanical Properties of Polyurethane Composites; Surface Chemistry.

[0240] To probe changes in the surface chemistry of the composites, X-ray photoelectron spectroscopy (XPS) was used to analyze changes in carbon bond populations pre- and post- UVB irradiation. Carbon 1s XPS spectra of the neat Pll and the composites showed three carbon species, namely C=C (farthest right peak, observed at binding energy (B.E) = 283.8 eV), C-C (peak observed at B.E. = 284.8 eV), C-O / C-N (peak observed at B.E. = 286.5 eV), and C=O / C=N (farthest left peak at B.E. = 289 eV) (FIGs. 4A-4C). Upon 30 hours of UVB irradiation, the C1 s XPS spectra of the irradiated PU and composites consistently showed peak broadening across all bond populations in comparison to their non-irradiated controls indicated by the increase in full-width half-maximum (FWHM) values (FIGs. 4D-4F, Table 4). This peak broadening is indicative of changes to the number and environment on the respective bonds within the sample, demonstrating chemical state changes induced by UVB-irradiation. The UVB-irradiated 0.25wt% p-1 ,7DHN-PU and 0.25wt% p-2,3DHN-PU both also exhibited peak broadening within their respective peaks but to a somewhat lesser extent than the UVB-irradiated PU. This was most evident with the C=O / C=N peak within the neat PU that showed an atomic % increase from approximately 1 .4% to 5.7% upon irradiation and exhibited peak broadening with a 54% increase in FWHM value. In contrast, the 0.25wt% p-1 ,7DHN-PU and 0.25wt% p-2,3DHN-PU both showed a smaller increase in atomic % from around 1 % to 2.5% upon irradiation with only a 30% and 40% increase in FWHM value, respectively. This peak broadening was also seen within the C-N / C-0 peak in which the neat PU showed a 30% increase in FWHM value in comparison to the 0.25wt% p-1 ,7DHN-PU and 0.25wt% p-2,3DHN-PU composites which showed a 16% and 17% increase post-UVB irradiation, respectively.Table 4. Carbon 1s XPS atomic percent distributions and FWHM values for pre- and post- UVB irradiated PU composites.

[0241] To further probe the photo-induced chemical changes to the composite surface, micro-Fourier transform infrared spectroscopy (p-FTIR) was conducted on the irradiated surfaces of all PU composites and compared against non-irradiated Pll (FIG. 4G). Specifically, in the region between 1150-1900 cm'1, distinct differences between the irradiated and non-irradiated PU were observed (FIG. 4H). There was a significant decrease in peak intensity at 1280 cm-1which likely corresponds to the polyurethane C- O stretch and C-0 stretching vibrations of aromatic esters.39 40There was also a noticeable increase in the peak at 1225 cm-1in all spectra that is likely attributed to C-0 stretch for saturated esters or C-N stretch of secondary amides. These changes to the C-0 functional groups in the p-FTIR spectra were also reflected in the broadening of these bond peaks in C1 s XPS spectra. Broadening of the peak at 1455 cm-1in the irradiated PU likely corresponds to degradation to the C-C stretch within the aromatic rings.41The disappearance of the peak at 1580 cm-1corresponding C=C of aromatic rings further indicates changes to the aromatic structure in the irradiated PU, but is preserved upon the addition of the p-1 ,7DHN and p-2,3DHN. Peak broadening and peak shifts between 1600-1652 cm-1in the irradiated PU can indicate C-C stretching of the aromatic ring, photo-oxidation of methylene bridges, degradation of alkenes, and primary amine N-H bonds.39Lastly, the appearance of peaks at around 1780 cm'1coupled with peak intensity decreases and broadening between 1699-1728 cm'1in the irradiated PU indicates the degradation of urethane and ester groups coupled with the formation of new carbonyl groups,39 42which also corresponds to the increase in atomic % and broadening of the C=O / C=N peak in the C1s XPS spectra. In conclusion, the XPS coupled with p-FTIR spectral analysis showed there are indeed photo-induced changes to the surface chemistry including degradation of aromatic structures, deformation of urethane linkages, and formation of new carbonyl bonds. These changesare evident in the irradiated neat Pll as well as the 0.25wt% p-1 .7DHN-PU and 0.25wt% p-2,3DHN-PU composites.

[0242] Example 2F - Evaluation of Mechanical Properties of Polyurethane Composites; Thermodegradation Behavior.

[0243] Thermogravimetric analysis (TGA) was done on the pre- and post- irradiated composites to probe changes to thermodegradation behavior (FIGs. 13A-13C). The UVB-irradiation neat Pll seemed to thermally degrade at a faster rate than its nonirradiated counterpart (FIG. 13A). In contrast, UVB-irradiated 0.25wt% p-1 ,7DHN-PU and 0.25wt% p-2,3DHN-PU showed very little change in its thermodegradation behavior after UVB-irradiation (FIGs. 13B & 13C), indicating that these materials had mitigated damages attributed to its respective p-DHN additives. Differential scanning calorimetry (DSC) was also performed on the composites pre- and post- irradiation to analyze changes to its bulk network properties; however, relatively negligible changes to the glass transition temperature (Tg) were observed, indicating there was insufficient radiation-induced polymer chain scission or additional crosslinking to cause significant bulk network alterations (FIGs. 14A-14C).

[0244] Example 2G - Evaluation of Mechanical Properties of Polyurethane Composites; Surface Morphology.

[0245] To determine how changes to the surface chemistry manifest into changes in surface morphology upon UVB irradiation, SEM micrographs were taken at the surface of the composites post-UVB irradiation. The neat, non-irradiated PU elastomers showed a relatively flat surface with minor debris and no visible cracks at the surface (FIG. 5A). Upon irradiation, the PU elastomer surface showed large and deep cracks throughout the surface (FIG. 5B). SEM images of 0.25wt% p-1 ,7DHN-PU and 0.25wt% p-2,3DHN- PU composites also showed cracks formed at the surface upon UVB irradiation (FIGs. 5C & 5D, respectively). However, the cracks observed were qualitatively thinner and shallower than those seen in the neat, irradiated PU. To confirm this, confocal microscopy was used to determine the width and depth of the cracks at the surface. The confocal microscopy images of the irradiated unfilled PU showed cracks with average widths of 11 ± 0.7 pm and average depths of 15 ± 1 pm (FIG. 5E). In contrast, 0.25wt% p-1 .7DHN-PU composites had cracks with average width of 2.9 ± 0.5 pm and average depths of 3.1 ± 0.6 pm (FIG. 5F). The 0.25wt% p-2,3DHN-PU composites had crackswith average width of 3.6 ± 0.5 m and average depths of 4.2 ± 0.4 pm (FIG. 5G). Surface cracks serve as stress concentrators during mechanical deformation which causes premature failure, thus the UVB-irradiated PU with the deepest and widest cracks consequently led to the greatest decrease in tensile mechanical properties.43Furthermore, the 0.25wt% p-1 ,7DHN-PU and p-2,3DHN-PU composites had cracks with a lower depth to width ratio than the irradiated PU, resulting in lower radius of curvature of the crack tip and less dramatic stress concentration, thus preventing premature failure during tensile testing (Table 5).43While cracks are indeed present in the p-1 .7DHN-PU and p-2,3DHN-PU composites, they did not lead to drastic, premature failure during application of tensile stress, demonstrating the protective effect of the nanoparticle additives. Confocal images of the irradiated composites at other tested wt% also showed much shallower cracks in comparison to the neat, irradiated PU material, which was also reflected in their maintained mechanical properties (FIGs. 15A & 15B, Table 5).Table 5. Crack width and depths of UVB-irradiated composites determined by confocal microscopy.*Crack depths and widths were too small to be reliably resolved via confocal microscopy

[0246] Conclusion for Examples 1 and 2: We demonstrated the synthesis of allomelanin-inspired nanomaterials, p-2,3DHN and p-1 ,7DHN, via polymerization of DHN-isomers, which yielded nanoparticles with enhanced radical scavenging activity and broadband absorption. We showed that these materials can be facilely incorporated and dispersed into commercial PU elastomers (e.g., FIGs. 2A, 2B, 2D, & 2E). These PU composites not only showed enhanced tensile mechanical properties (e.g., FIGs. 2C &2F) but maintained those properties after extensive UVB radiation (FIGs. 3A-3G) and gamma ray irradiation (FIGs. 16A-16D and FIGs. 17A-17C). While the allomelanin- inspired Pll composites showed definite photoinduced changes to their surface chemistry by XPS and p-FTIR analysis (e.g., FIGs. 4A-4H), these composites exhibited suppressed crack formation in comparison to their neat PU counterparts (e.g., FIGs. SASH), which is believed to have influenced the preservation of their mechanical properties post-irradiation.

[0247] While the above examples demonstrate enhanced desirable properties with PU, there are other potential polymer matrices that may be compatible with DHN- additives in view of the structural and / or functional similarities to PU (Table 6).Table 6. Potential Other Polymer Matrices that Can be Compatible with DHN- Additives.

[0248] Exemplary Experimental Aspects for the above Examples:

[0249] Materials: 1 ,8 dihydroxynapthalene (1 ,8DHN) (95+%) was purchased from Matrix Scientific. 1 ,7 dihydroxynapthalene (1 ,7DHN) (>98%) and 1 , 1 -diphenyl-2- picrylhydrazyl (DPPH) was purchased from Tokyo Chemical Industry Co. Ltd. 2,3 dihydroxynapthalene (2,3DHN) (98%) was purchased from Alfa Aesar. 4-Hydroxy- 2,2,6,6-tetramethylpiperidine 1-oxyl (4-hydroxy TEMPO) was purchased from Sigma- Aldrich. Sodium periodate, dopamine hydrochloride, sodium periodate (NalO4), HPLC grade acetonitrile (ACN), HPLC grade ethanol, were purchased from ThermoFisher Scientific. All chemicals were used as received. Ultrapure water was purified using Barnstead GenPure xCAD Plus system from ThermoFisher Scientific. Grids for transmission electron microscopy (TEM) were purchased from Electron Microscopy Sciences (EMS). Commercial polyurethane (PU) elastomer kit, VytaFlex20 liquid rubber, was purchased from Smooth-On.

[0250] Instrumentation: Scanning transmission electron microscopy (STEM) micrographs were taken on Hitachi HD2300 at an accelerating voltage of 200 kV. UV- Vis spectra of the nanoparticles at 0.01 mg / mL in ultrapure water were recorded using a Thermo Scientific Nanodrop 2000c spectrophotometer. Hydrodynamic diameters of the nanoparticles were measured using dynamic light scattering (DLS) with a Wyatt DynaPro NanoStar. Zetapotential of the nanoparticles were measured using Malvern Instruments Ltd, Nano ZS in ultrapure water at room temperature. Fourier Transform Infrared (FTIR) spectra was taken on ThermoScientific Nicolet iS50 spectrometer. DPPH colorimetric radical scavenging assay measurements were acquired using PerkinElmer Enspire Multimode Plate Reader. Solid-state UV-Vis / NIR transmission spectra were taken on Perkin Elmer LAMBDA 1050+. SEM images were acquired on Hitachi SU8030 and an 18 nm osmium coating was applied to sample prior to imaging. Confocal microscopy images were taken on Olympus 3D Laser Confocal Microscope. Matrix-assisted Laser Desorption / lonization Time of Flight mass spectrometry (MALDI- TOF MS) spectra of nanoparticles were collected using a Bruker rapileX Tissuetyperconfigured with a laser source (1000-5000 shots, 1 kHz, laser beam attenuation 60- 40%) in negative ion mode. Continuous wave electron paramagnetic resonance (ERR) spectra were collected on a Bruker ELEXSYS E680 EPR spectrometer with a Bruker 4122 SHQE-W1 resonator. Tensile mechanical properties of the composites were measured on a TA Instruments RSA III. The UVB irradiation source used is a Spectronics X-15B lamp (15 W, 312 nm). XPS spectra were collected on a ThermoScientific Nexsa G2 and spectra deconvolution was done using Advantage software (version 6.6) using Smart background subtraction and peaking fitting using the Simplex algorithm. Micro-FTIR ATR spectra was acquired on Bruker LIIMOS FTIR microscope using 64 scans. Thermogravimetric analysis (TGA) was collected on TA Instruments TGA 5500 under a nitrogen atmosphere using AI2O3 pans heating from 25 °C to 500 °C at 10°C / min. Differential scanning calorimetry (DSC) was performed on a TA Instruments DSC 250 at a ramp rate of 10 °C / min in Tzero aluminum pans.

[0251] Synthesis of Melanin Nanoparticles: The synthesis of PDA was based off a previously reported procedure with modifications.44Briefly, 150 mg of dopaminehydrochloride monomer was dissolved in 100 mL of ultrapure water and injected with a solution of NaOH (1 M, 0.75 mL). The reaction was allowed to proceed for 20 hours before being centrifuged and washed three times with ultrapure water.

[0252] The synthesis of p-1 ,8DHN was based off a previously reported procedure.33Briefly, 150 mg of 1 ,8DHN was dissolved in 7.5 mL of ACN and stirred for a few minutes before adding 142.5 mL of ultrapure water to the mixture. This solution was injected with a 1 mL solution containing NalO4 (0.47 mmol, 100.15 mg). The reaction was allowed to proceed for 20 hours before being centrifuged and washed with ultrapure water (11000 rpm, 10 minutes) three times.

[0253] p-1 ,7DHN and p-2,3DHN were prepared in a similar manner to the p-1 ,8DHN.For p-1 ,7DHN, 150 mg of 1 ,7DHN monomer was dissolved in 7.5 mL of ACN and stirred for a few minutes before adding 142.5 mL of ultrapure water to the mixture. This solution was then injected with a 2 mL solution containing NalO4 (0.94 mmol, 200.3 mg). The reaction was allowed to proceed for 20 hours before being centrifuged and washed with ultrapure water (11000 rpm, 10 minutes) three times. To prepare p-2,3DHN, 150 mg of 2,3DHN monomer was dissolved in 7.5 mL of ACN and stirred for a few minutes before adding 142.5 mL of ultrapure water to the mixture. This solution was injected with a 1 mL solution containing NalO4 (0.47 mmol, 100.15 mg). The reaction was allowed toproceed for only 1 hour before being centrifuged and washed with ultrapure water (11000 rpm, 10 minutes) three times.

[0254] All nanoparticles were lyophilized overnight before the addition to the Pll composites.

[0255] DPPH Radical Scavenging Assay: An DPPH radical scavenging activity of the melanin nanoparticles was based off a previously reported procedure with modifications.33Briefly, DPPH (0.2 mM) stock solution was prepared in 95% (v / v) ethanol. The melanin nanoparticles were aged 2 weeks post-synthesis to be utilized in the assay. Two duplicate sets of melanin nanoparticle solutions made up of 10, 20, 30, 40, and 50 pg of nanoparticles in 100pL of ultrapure water were prepared. In one set, 1.8 mL of the DPPH stock solution (0.2 mM) was added, pipette mixed, and left to sit in the dark for 20 minutes. After 20 minutes, all solutions were read on a plate reader at 516 nm (A!) To the other set of melanin nanoparticle solutions, 1.8 mL of 95% (v / v) ethanol was added to each make “blank” solutions and its absorbance at 516 nm was measured (A2). Finally, 1 .8 mL of the diluted DPPH stock solution (0.2 mM) was added to 100 pL of ultrapure water and its absorbance at 516 nm was measured (40) To calculate the radical scavenging activity at each concentration, the following equation was utilized:

[0256] Fabrication of PU Composites: The PU elastomer composites were made from a commercial PU kit (VytaFlex20, Smooth-On) composed of a part A mixture of polyols and a part B component of isocyanates. The appropriate lyophilized nanoparticle additives were added to the less viscous part B component, sonicated for 1.5 hours, and centrifugally mixed (2500 rpm, 1 min) to ensure even dispersion. Then, the part A mixture and part B component were added together and centrifugally mixed in a 1 :1 mass ratio in a centrifugal mixer (2500 rpm, 1 min), poured into a silicone mold, cured at room temperature for 16 hours, then heat cured in the oven for 8 hours at 65°C. The neat PU elastomer was fabricated in the same procedure, omitting addition of lyophilized nanoparticles.

[0257] Tensile Mechanical Testing of Composites: To prepare samples for tensile testing, the Pll composites were cut into rectangular strips (3 mm x 15 mm) and inserted between two clamps with an initial gap of 10 mm and were stretched at a rate of 0.2 mm / s.

[0258] UVB Irradiation of Composites: PU elastomer samples were situated 8 cm away from a UVB lamp (15 W, 312 nm) and irradiated for 30 hours. The output of the lamp was measured to be 3500 W / cm2.

[0259] MALDI-TOF MS: Nanoparticles were dissolved in ethyl acetate (1 mg / ml) and added to a solution of a-cyano-4-hydroxycinnamic acid (50% acetonitrile, 0.1 % TFA in DI water, saturated) in a ratio of 1 :10. Sample-matrix solution (1 pL ) was dropcasted and allowed to dry prior to mass analysis. Samples were then analyzed using a Bruker rapileX Tissuetyper in negative ion mode (1000-5000 shots, 1 kHz, laser beam attenuation 60-40%).

[0260] EPR Spectroscopy: Nanoparticle samples were prepared in 5mg / mL solutions in water and added to quartz capillaries (1 .50 mm i.d., 1 .80 mm o.d.) at equal volumes. Continuous wave EPR spectra were collected at X-band (~9.6 GHz) on a Bruker ELEXSYS E680 EPR spectrometer with a Bruker 4122 SHQE-W1 resonator and measurements were performed with a magnetic field modulation amplitude of 2 G, modulation frequency of 100 kHz, and non-saturating microwave power of 1.586 mW. The reported spectra are an average of 32 scans as was subsequently baseline corrected and doubly integrated in Origin 2022. A calibration curve was prepared by measuring EPR spectra of 4-hydroxy TEMPO at various concentrations (5,10,100, 500 pM) and utilized to determine concentration of radicals.

[0261] References:(1 ) Lindsley, W. G.; Martin, S. B.; Thewlis, R. E.; Sarkisian, K.; Nwoko, J. O.; Mead, K. R.; Noti, J. D. Effects of Ultraviolet Germicidal Irradiation (UVGI) on N95 Respirator Filtration Performance and Structural Integrity. Journal of Occupational and Environmental Hygiene 2015, 12 (8), 509-517.(2) Tapia-Guerrero, Y. S.; Del Prado-Audelo, M. L.; Borbolla-Jimenez, F. V.; Giraldo Gomez, D. M.; Garcia- Aguirre, I.; Colin-Castro, C. A.; Morales-Gonzalez, J. A.; Leyva- Gomez, G.; Magana, J. J. Effect of UV and Gamma Irradiation Sterilization Processes inthe Properties of Different Polymeric Nanoparticles for Biomedical Applications.Materials 2020, 73 (5), 1090.(3) Nambiar, S.; Yeow, J. T. W. Polymer-Composite Materials for Radiation Protection. ACS Appl. Mater. Interfaces 2012, 4 (11), 5717-5726.(4) Decker, C.; Zahouily, K. Photodegradation and Photooxidation of Thermoset and UV-Cured Acrylate Polymers. Polymer Degradation and Stability 1999, 64 (2), 293-304.(5) Korkmaz, Y.; Giiltekin, K. Effect of UV Irradiation on Epoxy Adhesives and Adhesively Bonded Joints Reinforced with BN and B4C Nanoparticles. Polymer Degradation and Stability 2022, 202, 110004.(6) Abbas, M. I.; Alahmadi, A. H.; Elsafi, M.; Alqahtani, S. A.; Yasmin, S.; Sayyed, M. I.; Gouda, M. M.; El-Khatib, A. M. Effect of Kaolin Clay and ZnO-Nanoparticles on the Radiation Shielding Properties of Epoxy Resin Composites. Polymers 2022, 14 (22), 4801.(7) Muthamma, M. V.; Bubbly, S. G.; Gudennavar, S. B.; Narendranath, K. C. S. Poly(Vinyl Alcohol)-Bismuth Oxide Composites for X-ray and F-ray Shielding Applications. J of Applied Polymer Sci 2019, 736 (37), 47949.(8) Zhao, Y.; Li, G.; Dai, X.; Liu, F.; Dong, Z.; Qiu, X. AO-Resistant Properties of Polyimide Fibers Containing Phosphorous Groups in Main Chains. Chin J Polym Sci 2016, 34 (12), 1469-1478.(9) Murphy, J. Additives for Plastics Handbook', Elsevier Science, 2001.(10) Kurahatti, R.; Surendranathan, A.; Kori, S.; Singh, N.; Kumar, A.; Srivastava, S. Defence Applications of Polymer Nanocomposites. DSJ 2010, 60 (5), 551-563.(11) Tiwari, V. K.; Kulriya, P. K.; Avasthi, D. K.; Maiti, P. Radiation-Resistant Behavior of Poly(Vinylidene Fluoride) / Layered Silicate Nanocomposites. ACS Appl. Mater.Interfaces 2009, 7 (2), 311-318.(12) Naveed Ul Haq, A.; Nadhman, A.; Ullah, I.; Mustafa, G.; Yasinzai, M.; Khan, I. Synthesis Approaches of Zinc Oxide Nanoparticles: The Dilemma of Ecotoxicity. Journal of Nanomaterials 2017 , 2017, 1-14.(13) Verma, S.; Sarma, B.; Chaturvedi, K.; Malvi, D.; Srivastava, A. K. Emerging Graphene and Carbon Nanotube-Based Carbon Composites as Radiations Shielding Materials for X-Rays and Gamma Rays: A Review. Composite Interfaces 2023, 30 (2), 223-251.(14) Kuo, L.; Luijten, B. J.; Li, S.; De Moraes, A. C. M.; Silvaroli, A. J.; Wallace, S. G.; Hui, J.; Downing, J. R.; Shull, K. R.; Hersam, M. C. Sterilizable and Reusable UV- Resistant Graphene-Polyurethane Elastomer Composites. ACS Appl. Mater. Interfaces 2022, 14 (47), 53241-53249.(15) Fan, W.; Wang, J.; Zhang, Z.; Li, Z. Synergistic Enhancement of UV-Resistance and Electrical Conductivity of Waterborne Polyurethane Composite with Combination of Functionalized 2D Graphene Oxide and 1 D Nanocellulose. Progress in Organic Coatings 2021 , 151, 106017.(16) Bussy, C.; Ali-Boucetta, H.; Kostarelos, K. Safety Considerations for Graphene: Lessons Learnt from Carbon Nanotubes. Acc. Chem. Res. 2013, 46 (3), 692-701.(17) Deng, Q.; He, B.; Shen, M.; Ge, J.; Du, B.; Zeng, L. First Evidence of Hindered Amine Light Stabilizers As Abundant, Ubiquitous, Emerging Pollutants in Dust and Air Particles: A New Concern for Human Health. Environ. Sci. Technol. 2024, 58 (2), 1349- 1358.(18) Brenner, M.; Hearing, V. J. The Protective Role of Melanin Against UV Damage in Human Skin t Photochem & Photobiology 2008, 84 (3), 539-549.(19) Moses, D. N.; Harreld, J. H.; Stucky, G. D.; Waite, J. H. Melanin and Glycera Jaws. Journal of Biological Chemistry 2006, 281 (46), 34826-34832.(20) Zhang, X.; Peng, Y.; Wang, X.; Ran, R. Melanin-lnspired Conductive Hydrogel Sensors with Ultrahigh Stretchable, Self-Healing, and Photothermal Capacities. ACS Appl. Polym. Mater. 2021 , 3 (4), 1899-1911.(21) Zhou, Z.; Wang, X.; Yu, H.; Yu, C.; Zhang, F. Dynamic Cross-Linked Polyurea / Polydopamine Nanocomposites for Photoresponsive Self-Healing and Photoactuation. Macromolecules 2022, 55 (6), 2193-2201.(22) Yang, L.; Phua, S. L.; Toh, C. L.; Zhang, L.; Ling, H.; Chang, M.; Zhou, D.; Dong, Y.; Lu, X. Polydopamine-Coated Graphene as Multifunctional Nanofillers in Polyurethane. RSC Adv. 2013, 3 (18), 6377.(23) Kim, Y.; Kim, J. Carbonization of Polydopamine-Coating Layers on Boron Nitride for Thermal Conductivity Enhancement in Hybrid Polyvinyl Alcohol (PVA) Composites. Polymers 2020, 12 (6), 1410.(24) Lv, J.; Wang, H.; Liu, Y.; Chen, J.; Chen, H.; Xu, J.; Sun, J.; Zhao, H.; Zhu, C. Nanocomposite Enhanced Radiation Resistant Effects in Polyurethane Elastomer with Low Fraction of Polydopamine Nanoparticles. Composites Science and Technology 2020, 186, 107908.(25) Cordero, R. J. B.; Casadevall, A. Functions of Fungal Melanin beyond Virulence. Fungal Biology Reviews 2017, 31 (2), 99-112.(26) Dadachova, E.; Casadevall, A. Ionizing Radiation: How Fungi Cope, Adapt, and Exploit with the Help of Melanin. Current Opinion in Microbiology 2008, 11 (6), 525-531.(27) Dadachova, E.; Casadevall, A. Melanin and Resistance to Ionizing Radiation in Fungi. In Extremophiles Handbook; Horikoshi, K., Ed.; Springer Japan: Tokyo, 2011 ; pp 1147-1157.(28) Cassaro, A.; Pacelli, C.; Baque, M.; Cavalazzi, B.; Gasparotto, G.; Saladino, R.; Botta, L.; Bdttger, U.; Rabbow, E.; De Vera, J.; Onofri, S. Investigation of Fungal Biomolecules after Low Earth Orbit Exposure: A Testbed for the next Moon Missions. Environmental Microbiology 2022, 24 (7), 2938-2950.(29) Zhdanova, N. N.; Zakharchenko, V. A.; Vember, V. V.; Nakonechnaya, L. T. Fungi from Chernobyl: Mycobiota of the Inner Regions of the Containment Structures of the Damaged Nuclear Reactor. Mycological Research 2000, 104 (12), 1421-1426.(30) Dadachova, E.; Bryan, R. A.; Huang, X.; Moadel, T.; Schweitzer, A. D.; Aisen, P.; Nosanchuk, J. D.; Casadevall, A. Ionizing Radiation Changes the Electronic Properties of Melanin and Enhances the Growth of Melanized Fungi. PLoS ONE 2007, 2 (5), e457.(31) Pacelli, C.; Bryan, R. A.; Onofri, S.; Selbmann, L.; Zucconi, L.; Shuryak, I.;Dadachova, E. Survival and Redox Activity of Friedmanniomyces Endolithicus, anAntarctic Endemic Black Meristematic Fungus, after Gamma Rays Exposure. Fungal Biology 2018, 722 (12), 1222-1227.(32) Singla, S.; Htut, K. Z.; Zhu, R.; Davis, A.; Ma, J.; Ni, Q. Z.; Burkart, M. D.; Maurer, C.; Miyoshi, T.; Dhinojwala, A. Isolation and Characterization of Allomelanin from Pathogenic Black Knot Fungus— a Sustainable Source of Melanin. ACS Omega 2021 , 6 (51 ), 35514-35522.(33) Zhou, X.; McCallum, N. C.; Hu, Z.; Cao, W.; Gnanasekaran, K.; Feng, Y.; Stoddart, J. F.; Wang, Z.; Gianneschi, N. C. Artificial Allomelanin Nanoparticles. ACS Nano 2019, 73 (10), 10980-10990.(34) McCallum, N. C.; Son, F. A.; Clemons, T. D.; Weigand, S. J.; Gnanasekaran, K.; Battistella, C.; Barnes, B. E.; Abeyratne-Perera, H.; Siwicka, Z. E.; Forman, C. J.; Zhou, X.; Moore, M. H.; Savin, D. A.; Stupp, S. I.; Wang, Z.; Vora, G. J.; Johnson, B. J.; Farha, O. K.; Gianneschi, N. C. Allomelanin: A Biopolymer of Intrinsic Microporosity. J. Am. Chem. Soc. 2021 , 143 (10), 4005-4016.(35) Riley, P. A. Melanin. The International Journal of Biochemistry & Cell Biology 1997, 29 (11 ), 1235-1239.(36) Panzella, L.; Gentile, G.; D’Errico, G.; Della Vecchia, N. F.; Errico, M. E.;Napolitano, A.; Carfagna, C.; d’Ischia, M. Atypical Structural and n-Electron Features of a Melanin Polymer That Lead to Superior Free-Radical-Scavenging Properties. Angew. Chem. Int. Ed. 2013, 52 (48), 12684-12687.(37) Schweitzer, A. D.; Howell, R. C.; Jiang, Z.; Bryan, R. A.; Gerfen, G.; Chen, C.-C.; Mah, D.; Cahill, S.; Casadevall, A.; Dadachova, E. Physico-Chemical Evaluation of Rationally Designed Melanins as Novel Nature-Inspired Radioprotectors. PLoS ONE 2009, 4 (9), e7229.(38) Liu, S.; Feng, Y.; Wang, Y.; Zhang, S.; Yu, M.; Wang, X.; Zhou, C. Interfacial Enhancement by Constructing a “Flexible-Rigid” Structure between High-Modulus Fillers and Low-Modulus Matrix in Carbon Fiber / Silicone Rubber Composites. Progress in Organic Coatings 2024, 797, 108468.(39) Bruckmoser, K.; Resch, K. Investigation of Ageing Mechanisms in Thermoplastic Polyurethanes by Means of IR and Raman Spectroscopy. Macromolecular Symposia 2014, 339 (1), 70-83.(40) Smith, B. C. Infrared Spectroscopy of Polymers, VIII: Polyesters and the Rule of Three. Spectroscopy 2022, 31 (11), 25-28.(41) Smith, B. C. The Infrared Spectroscopy of Alkenes. Spectroscopy 2016, 28-34.(42) Smith, B. C. Infrared Spectroscopy of Polymers XIII: Polyurethanes. Spectroscopy 2023, 14-16.(43) Creton, C.; Ciccotti, M. Fracture and Adhesion of Soft Materials: A Review. Rep. Prog. Phys. 2016, 79 (4), 046601.(44) Biyashev, D.; Siwicka, Z. E.; Onay, II. V.; Demczuk, M.; Xu, D.; Ernst, M. K.; Evans, S. T.; Nguyen, C. V.; Son, F. A.; Paul, N. K.; McCallum, N. C.; Farha, O. K.; Miller, S. D.; Gianneschi, N. C.; Lu, K. Q. Topical Application of Synthetic Melanin Promotes Tissue Repair, npj Regen Med 2023, 8 (1 ), 61 .(45) U.S. Pat. 8,334,356.(46) Gotro, J.; Prime, R.B. Thermosets. Encyclo. of Polymer Sci. and Tech. 2017.(47) Lewis, B., et al. Glassy Dynamics of Epoxy-Amine Thermosets Containing Dynamic, Aromatic Disulfides. Macromolecules. 2024, 57, 15, 7112-7122.(48) Pham, H. Q.; Marks, M. J. Epoxy Resins. Ulmann’s Encyclo. Indust. Chem. 2005.STATEMENTS REGARDING INCORPORATION BY REFERENCE AND VARIATIONS

[0262] All references throughout this application, for example patent documents including issued or granted patents or equivalents; patent application publications; and non-patent literature documents or other source material; are hereby incorporated by reference herein in their entireties, as though individually incorporated by reference, to the extent each reference is at least partially not inconsistent with the disclosure in this application (for example, a reference that is partially inconsistent is incorporated by reference except for the partially inconsistent portion of the reference).

[0263] The terms and expressions which have been employed herein are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments, exemplary embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention. The specific embodiments provided herein are examples of useful embodiments of the present invention and it will be apparent to one skilled in the art that the present invention may be carried out using a large number of variations of the product, product components, methods steps set forth in the present description. As will be obvious to one of skill in the art, products and methods useful for the present invention can include a large number of optional composition and processing elements and steps.

[0264] As used herein, the singular forms "a", "an", and "the" include plural reference unless the context clearly dictates otherwise. Thus, for example, reference to "a cell" includes a plurality of such cells and equivalents thereof known to those skilled in the art. As well, the terms "a" (or "an"), "one or more" and "at least one" can be used interchangeably herein. It is also to be noted that the terms "comprising", "including", and "having" can be used interchangeably. The expression “of any of embodiments XX- YY” (wherein XX and YY refer to embodiment numbers) is intended to provide a multiple dependencies in the alternative form, and in some embodiments is interchangeable with the expression “as in any one of embodiments XX- YY.”

[0265] When a group of substituents is disclosed herein, it is understood that all individual members of that group and all subgroups, are disclosed separately. When a Markush group or other grouping is used herein, all individual members of the group and all combinations and subcombinations possible of the group are intended to be individually included in the disclosure. When a compound is described herein such that a particular isomer, enantiomer or diastereomer of the compound is not specified, for example, in a formula or in a chemical name, that description is intended to include each isomers and enantiomer of the compound described individual or in any combination.

[0266] Whenever a range is given in the specification, for example, a temperature range, a time range, or a composition or concentration range, all intermediate ranges and subranges, as well as all individual values included in the ranges given are intended to be included in the disclosure. It will be understood that any subranges or individual values in a range or subrange that are included in the description herein can be excluded from the embodiments herein.

[0267] All patents and publications mentioned in the specification are indicative of the levels of skill of those skilled in the art to which the invention pertains. References cited herein are incorporated by reference herein in their entirety to indicate the state of the art as of their publication or filing date and it is intended that this information can be employed herein, if needed, to exclude specific embodiments that are in the prior art.

[0268] As used herein, “comprising” is synonymous with "including," "containing," or "characterized by," and is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. As used herein, "consisting of" excludes any element, step, or ingredient not specified in the said embodiment. As used herein, "consisting essentially of" does not exclude materials or steps that do not materially affect the basic and novel characteristics of the embodiment. In each instance herein any of the terms "comprising", "consisting essentially of" and "consisting of" may be replaced with either of the other two terms. The invention illustratively described herein suitably may be practiced in the absence of any element or elements, limitation or limitations which is not specifically disclosed herein.

[0269] One of ordinary skill in the art will appreciate that starting materials, biological materials, reagents, synthetic methods, purification methods, analytical methods, assay methods, and biological methods other than those specifically exemplified can be employed in the practice of the invention without resort to undue experimentation. All art-known functional equivalents, of any such materials and methods are intended to be included in this invention. The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention that in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments and optional features, modification and variation of the concepts herein disclosed may beresorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by embodiments herein.

[0270] Without wishing to be bound by any particular theory, there may be discussion herein of beliefs or understandings of underlying principles relating to the products and methods disclosed herein. It is recognized that regardless of the ultimate correctness of any mechanistic explanation or hypothesis, an embodiment of the invention can nonetheless be operative and useful.

[0271] In general, the terms and phrases used herein have their art-recognized meaning, which can be found by reference to standard texts, journal references and contexts known to those skilled in the art.

Claims

WE CLAIM:

1. A nanoadditive comprising a synthetic melanin-inspired nanoparticle, wherein: the synthetic melanin-inspired nanoparticle comprises a plurality of covalently- linked artificial melanin precursors, and each artificial melanin precursor independently comprises an artificial allomelanin precursor, an artificial eumelanin precursor, or a structural isomer thereof.

2. The nanoadditive of claim 1 , wherein each artificial melanin precursor independently comprises a substituted or unsubstituted catechol-based compound, a substituted or unsubstituted dihydroxynaphthalene-based compound, a substituted or unsubstituted indole-based compound, a substituted or unsubstituted dopamine-based compound, or any combination thereof.

3. The nanoadditive of any one of the preceding claims, wherein each artificial melanin precursor independently is a substituted or unsubstituted dihydroxynaphthalene-based compound, or a substituted or unsubstituted dopamine-based compound.

4. The nanoadditive of any one of the preceding claims, wherein each artificial melanin precursor independently is a substituted or unsubstituted: dopamine monomer, 1 ,8-dihydroxynaphthalene monomer, tyrosine monomer, tyramine monomer, catecholamine, or any combination thereof.

5. The nanoadditive of any one of the preceding claims, wherein each artificial melanin precursor independently comprises substituted or unsubstituted naphthalene.

6. The nanoadditive of any one of the preceding claims, wherein each artificial melanin precursor independently comprises a structural isomer of a substituted or unsubstituted 1 ,8-dihydroxynaphthalene monomer.

7. The nanoadditive of claim 6, wherein the structural isomer of the substituted or unsubstituted 1 ,8-dihydroxynaphthalene monomer independently is a 1 ,7- dihydroxynaphthalene monomer or a 2,3-dihydroxynaphthalene monomer.

8. The nanoadditive of claim 6 or 7, wherein the structural isomer independently is more hydrophobic than the substituted or unsubstituted 1 ,8- dihydroxynaphthalene monomer.

9. The nanoadditive of any one of the preceding claims, wherein each artificial melanin precursor independently is a substituted or unsubstituted 1 ,7- dihydroxynaphthalene monomer.

10. The nanoadditive of any one of the preceding claims, wherein each artificial melanin precursor independently is a substituted or unsubstituted 2,3- dihydroxynaphthalene monomer.11 . The nanoadditive of any one of claims 6-10, wherein the synthetic melanin- inspired nanoparticle is characterized by a radical scavenging activity greater than that of a nanoparticle consisting of a plurality of covalently-linked 1 ,8- dihydroxynaphthalene monomers or polydopamine monomers having the same diameter as the synthetic melanin-inspired nanoparticle under otherwise identical conditions.

12. The nanoadditive of any one of the preceding claims, wherein each artificial melanin precursor independently comprises a structure having the formula FX1 , FX2, FX3, or FX4:

13. The nanoadditive of any one of the preceding claims, wherein each artificial melanin precursor is free of nitrogen.

14. The nanoadditive of any one of the preceding claims, wherein the synthetic melanin-inspired nanoparticle comprises between 3 and 50 covalently-linked artificial melanin precursors.

15. The nanoadditive of any one of the preceding claims, wherein the synthetic melanin-inspired nanoparticle comprises between 3 and 25 covalently-linked artificial melanin precursors.

16. The nanoadditive of any one of the preceding claims, wherein the synthetic melanin-inspired nanoparticle comprises between 5 and 20 covalently-linked artificial melanin precursors.

17. The nanoadditive of any one of the preceding claims, wherein the synthetic melanin-inspired nanoparticle is hydrophobic.

18. The nanoadditive of any one of the preceding claims, wherein the nanoadditive comprises between 0 wt.% and 0.5 wt.% of non-covalently-linked artificial melanin precursors or monomers based on the total weight of the nanoadditive.

19. The nanoadditive of any one of the preceding claims, wherein the synthetic melanin-inspired nanoparticle has a shape characterized by a sphere and a diameter selected from the range of 100 nm to 300 nm.

20. The nanoadditive of any one of the preceding claims, wherein the synthetic melanin-inspired nanoparticle is a porous synthetic melanin-inspired nanoparticle.21 . The nanoadditive of any one of the preceding claims being dispersed in a solvent or solvent mixture, thereby forming a nanoadditive dispersion.

22. The nanoadditive of claim 21 , wherein the solvent or solvent mixture is at least 50% water.

23. The nanoadditive of claim 21 or 22, wherein the synthetic melanin-inspired nanoparticle in the nanoadditive dispersion is characterized by a zeta potential, or an average zeta potential, selected from the range of -50 mV to -10 mV.

24. The nanoadditive of claim 21 , wherein the solvent or solvent mixture is an inorganic solvent or inorganic solvent mixture and the synthetic melanin-inspired nanoparticle is miscible in the inorganic solvent or inorganic solvent mixture.

25. The nanoadditive of any one of the preceding claims, wherein the nanoadditive is non-toxic, biocompatible, degradable, or any combination thereof.

26. The nanoadditive of any one of the preceding claims, wherein the nanoadditive is characterized by a green pigmentation, a black pigmentation, a pink pigmentation, or a tan pigmentation.

27. A polymer nanocomposite comprising: the nanoadditive of any one of the preceding claims; and a polymeric material.

28. A polymer nanocomposite comprising: a nanoadditive, wherein the nanoadditive comprises: a synthetic melanin-inspired nanoparticle comprising a plurality of covalently-linked artificial melanin precursors, wherein each artificial melanin precursor independently comprises an artificial allomelanin precursor, an artificial eumelanin precursor, or a structural isomer thereof; and a polymeric material.

29. The polymer nanocomposite of any one of the preceding claims, wherein the synthetic melanin-inspired nanoparticle is present in the polymer nanocomposite in an amount of between 0.05 wt.% and 10 wt.% based on the total weight of the polymer nanocomposite.

30. The polymer nanocomposite of any one of the preceding claims, wherein the synthetic melanin-inspired nanoparticle is present in the polymer nanocomposite in an amount of between 0.1 wt.% and 1 wt.% based on the total weight of the polymer nanocomposite.31 . The polymer nanocomposite of any one of the preceding claims, wherein the polymer nanocomposite is characterized by at least one mechanical property that is enhanced as compared to a baseline mechanical property of the polymeric material without the nanoadditive.

32. The polymer nanocomposite of claim 31 , wherein the at least one mechanical property comprises: (i) ultimate tensile strength; (ii) elongation; (iii) toughness; (iv) elasticity; (v) resistance to crack formation; (vi) preservation of the polymer nanocomposite surface chemistry; (vii) radiation resistance; (viii) broadband absorption; (ix) radical scavenging behavior; (x) light energy quenching; or (xi) any combination thereof.

33. The polymer nanocomposite of claim 32, wherein the radiation resistance comprises resistance to UV radiation, gamma ray radiation, and / or x-ray radiation.

34. The polymer nanocomposite of any one of the preceding claims, wherein the polymeric material comprises a plurality of cross-linked polymers.

35. The polymer nanocomposite of any one of the preceding claims, wherein the polymeric material comprises a block copolymer.

36. The polymer nanocomposite of any one of the preceding claims, wherein the polymeric material comprises an elastomer, a resin, or a silicone.

37. The polymer nanocomposite of any one of the preceding claims, wherein the polymeric material comprises polyurethane, polyolefins, polyesters, polyamides, polycarbonates, polysiloxanes, or a blend thereof.

38. The polymer nanocomposite of any one of the preceding claims, wherein the polymeric material comprises a thermoplastic polymer or a thermosetting polymer.

39. The polymer nanocomposite of any one of the preceding claims, wherein the polymeric material is selected from the group consisting of epoxy resins, silicone elastomers, bismaleimide resins, cyanate ester resins, and epoxy-amine thermosets.

40. The polymer nanocomposite of any one of the preceding claims, wherein the polymeric material comprises polyurethane.41 . The polymer nanocomposite of any one of the preceding claims, wherein the polymeric material is a polyurethane elastomer or a polyurethane resin.

42. The polymer nanocomposite of any one of the preceding claims, wherein each artificial melanin precursor independently comprises a structure having the formula FX1, FX2, FX3, or FX4:

43. A method of protecting a polymeric material from ionizing radiation, the method comprising incorporating the nanoadditive of any one of the preceding claims into the polymeric material.

44. A radiation protective nanoadditive for a polyurethane nanocomposite comprising the nanoadditive or the synthetic melanin-inspired nanoparticle of any one of the preceding claims.

45. A method of generating a polymer nanocomposite, the method comprising: providing a plurality of artificial melanin monomers comprising artificial allomelanin precursors, artificial eumelanin precursors, and / or structural isomers thereof; polymerizing the plurality of artificial melanin monomers to form a synthetic melanin-inspired nanoparticle; and contacting at least a portion of a polymeric material with the synthetic melanin- inspired nanoparticle to generate a polymer nanocomposite; wherein the synthetic melanin-inspired nanoparticle is present in the polymer nanocomposite in an amount of between 0.1 wt.% and 1 wt.% based on the total weight of the polymer nanocomposite; thereby generating a polymer nanocomposite.

46. The method of claim 45, wherein the contacting step comprises: contacting a first subcomponent of the polymeric material with the synthetic melanin-inspired nanoparticle to generate a nanoparticle-containing subcomponent; and combining the nanoparticle-containing subcomponent with a second subcomponent of the polymeric material to generate the polymer nanocomposite.

47. The method of claim 45 or 46, wherein the polymerizing step comprises oxidative oligomerization or polymerization.

48. The method of any one of claims 45-47, further comprising lyophilizing the synthetic melanin-inspired nanoparticle prior to the contacting step to generate a lyophilized synthetic melanin-inspired nanoparticle.

49. The method of any one of claims 45-48, wherein the polymeric material comprises an elastomer, a resin, or a silicone.

50. The method of any one of claims 45-49, wherein the polymeric material comprises polyurethane, polyolefins, polyesters, polyamides, polycarbonates, polysiloxanes, or a blend thereof.51 . The method of any one of claims 45-50, wherein the polymeric material comprises a thermoplastic polymer or a thermosetting polymer.

52. The method of any one of claims 45-51 , wherein the polymeric material is selected from the group consisting of epoxy resins, silicone elastomers, bismaleimide resins, cyanate ester resins, and epoxy-amine thermosets.

53. The method of any one of claims 46-52, wherein the polymeric material comprises polyurethane, and the first subcomponent of the polymeric material comprises isocyanate.

54. The method of claim 53, wherein the second subcomponent of the polymeric material comprises polyols.

55. The method of any one of claims 45-54, wherein the contacting step does not comprise an organic solvent, a surfactant, or an additional additive.

56. The method of any one of claims 45-55, wherein each artificial melanin precursor independently comprises a structure having the formula FX1 , FX2, FX3, or FX4:

57. A method of enhancing a mechanical property of a polymeric material, the method comprising: providing a plurality of artificial melanin monomers comprising a substituted or unsubstituted 1 ,8-dihydroxynaphthalene monomer or a structural isomer thereof; polymerizing the plurality of artificial melanin monomers to form a synthetic melanin-inspired nanoparticle; and contacting at least a portion of a polymeric material with the synthetic melanin- inspired nanoparticle to generate a polymer nanocomposite characterized by at least one enhanced mechanical property; wherein the synthetic melanin-inspired nanoparticle is present in the polymer nanocomposite in an amount of between 0.1 wt.% and 1 wt.% based on the total weight of the polymer nanocomposite; thereby enhancing a mechanical property of a polymeric material.

58. The method of claim 57, wherein the contacting step comprises: contacting a first subcomponent of the polymeric material with the synthetic melanin-inspired nanoparticle to generate a nanoparticle-containing subcomponent; and combining the nanoparticle-containing subcomponent with a second subcomponent of the polymeric material to generate the polymer nanocomposite characterized by at least one enhanced mechanical property.

59. The method of claim 58, wherein the polymeric material comprises polyurethane, the first subcomponent of the polymeric material comprises isocyanates, and the second subcomponent of the polymeric material comprises polyols.

60. The method of any one of claims 57-59, wherein the at least one enhanced mechanical property comprises: (i) ultimate tensile strength; (ii) elongation; (iii) toughness; (iv) elasticity; (v) resistance to crack formation; (vi) preservation of the polymer nanocomposite surface chemistry; (vii) radiation resistance; (viii) broadband absorption; (ix) radical scavenging behavior; (x) light energy quenching; or (xi) any combination thereof.61 . The method of any one of claims 57-60, wherein each artificial melanin monomer independently comprises a structure having the formula FX1 , FX2, or FX3:

Images