Catechol-containing adhesive polymer

Abstract

A catechol-containg adhesive polymer comprising (i) a poly (vinylcatechol-styrene), (ii) an organic solvent, wherein the organic solvent is partially miscible with water and is less dense than water, and (ii) optionally a filler; and a method of use in moist, wet, and underwater adhesion.

Description

70938-02CATECHOL-CONTAINING ADHESIVE POLYMERCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. provisional patent application no. 63 / 727,821, which was filed December 4, 2024, and which is hereby incorporated by reference in its entirety.STATEMENT OF GOVERNMENT SUPPORT

[0002] This invention was made with government support under N00014-22-C-2017 awarded by the Office of Naval Research. The government has certain rights in the invention.TECHNICAL FIELD

[0003] The present disclosure relates to a catechol-containing adhesive polymer that can be used on moist, wet, and underwater surfaces and is suitable for large-scale use in industrial settings.BACKGROUND

[0004] This section introduces aspects that may help facilitate a better understanding of the disclosure. Accordingly, these statements are to be read in this light and are not to be understood as admissions about what is or is not prior art.

[0005] Pendant catechol groups can be found in the post-translationally modified amino acid 3,4- dihydroxyphenylalanine (DOPA). This catechol-containing amino acid allows marine mussels to adhere to surfaces underwater. Catechols can form multiple chemical interactions with substrates, ranging from weak dispersion forces to covalent bonds. Catechol-containing polymers can have potential applications in various fields due to their diverse chemistry and functionalities (Science 1979, 212, 1038-1040; J Biol Chem 1983, 258, 2911-2915), e.g., adhesives, coatings, drug delivery systems, and hydrogels for tissue engineering. These adhesives have incorporated catechol moieties into different polymeric backbones to achieve strong adhesive properties in both dry and underwater environments. For instance, poly(thioctic acylamino catechol) was reported to display good adhesion strength aided by the hydrophobic nature of the polymer backbone as well as via the formation of iron-catechol complexes responsible for cross-linking70938-02(Natl Sci Review 2023, 10). The epoxy resins show stronger adhesion to aluminum and stainless- steel substrates when the surface of metal substrates is prepared with a polyfglycidyl methacrylate-co-(N-(3,4-dihydroxyphenethyl)methacrylamide] copolymer containing 15% catechol units (ACS Appl Polym Mater 2020, 2, 1500-1507). Polyhydroxyurethane thermoset adhesives were shown to have enhanced mechanical and adhesive properties in dry conditions by incorporating 3.9 mol% dopamine into the formulation (Chem Eng 2018, 6, 14936-14944). However, the translation of any novel adhesive chemistry from academic research to real-world applications remains challenging, particularly given the lack of substantial advancements in adhesive chemistry beyond acrylates, epoxies, and urethanes introduced to markets over half a century ago. The selection of a well-defined catechol-containing polymer system, its facile synthesis, and evaluation of performance closer to real-world uses beyond the confines of the research lab are still needed.

[0006] It is an object of the present disclosure to provide a catechol-containing adhesive polymer that maintains strong adhesion underwater at various temperatures, extended durations, and flow conditions. This and other objects and advantages, as well as inventive features, will be apparent from the detailed description.SUMMARY

[0007] Provided is an adhesive polymer comprising (i) a poly(vinylcatechol-styrene) (PVCS) copolymer comprising a 3, 4-dihydroxy styrene monomer and a styrene monomer, (ii) an organic solvent, wherein the organic solvent is partially miscible with water and is less dense than water and (iii) optionally a filler.

[0008] In some embodiments, the PVCS can be present in a concentration at or about 0.1 g / mL - 1.5 g / mL of the polymer. In some embodiments, the PVCS can be present in a concentration at or about 0.3 g / mL - 1.2 g / mL of the polymer. The filler can be an inorganic filler. Any suitable inorganic filler can be used. The inorganic filler is selected from the group consisting of natural clay, calcium carbonate (CaCCh), zinc oxide (ZnO), synthetic clay, and a combination of two or more thereof. In some embodiments, the inorganic filler is CaCCh. In some embodiments, the filler is a polymeric material. Any suitable polymeric material can be used. In some embodiments, the polymeric material is selected from the group consisting of protein, polysaccharide, rubber, and any combination thereof. In some embodiments, the polymeric material is a rubber selected from a natural rubber or a synthetic rubber. In some embodiments, the rubber can be a recycled70938-02 tire rubber (crumb rubber) or acrylate-butadiene rubber (ABR). In some embodiments, the inorganic filler can be present at or about 1 wt% - 20 wt% of the adhesive polymer.

[0009] Any suitable organic solvent, which is partially miscible with water and is less dense than water can be used. The organic solvent can be selected from the group consisting of a ketone, a hydrophobic solvent, and a mixture of a ketone and a hydrophobic solvent. In some embodiments, the ketone is acetone, butanone, or methyl ethyl ketone (MEK). Desirably, the ketone is MEK. In some embodiments, the hydrophobic solvent is hexane, cyclohexane, butane, isobutane, or pentane. In some embodiments, the organic solvent can be a mixture of MEK and hexane. In some embodiments, the MEK and hexane can be present in a ratio of about 6: 1 to about 15: 1. Desirably, the ratio is about 9: 1.

[0010] In some embodiments, the adhesive polymer exhibits an adhesion value on a wet surface from about 0.5 MPa to about 3 MPa. In some embodiments, the adhesive polymer has a viscosity of about 0.05 Pa.s to about 10 Pa.s. In some embodiments, the adhesive polymer has a wet peel strength of about 0.4 N / mm to about 1 N / mm at a peel angle of 90 °.

[0011] Provided is a method of using the adhesive polymer, which method comprises applying the adhesive polymer to at least a first substrate, which is to be adhered to at least a second substrate, and adhering the first substrate and the second substrate to each other such that the adhesive polymer is sandwiched therebetween. The method can further comprise applying the adhesive polymer to the second substrate prior to adhering to the first substrate and the second substrate. At least one of the substrates can be (or has been) exposed to dry, moist, wet, or underwater conditions. In some embodiments, the first substrate and / or the second substrate comprise a metal, wood, plastic, ceramic, polyurethane, rubber, Teflon®, polypropylene, or a combination of two or more thereof. In some embodiments, the first substrate and / or the second substrate is a metal selected from steel or aluminum. In some embodiments, the first substrate and / or the second substrate is polyurethane.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The present disclosure will be more readily understood from the detailed description of embodiments presented below, considered in conjunction with the attached drawings of which:

[0013] FIG. 1A shows the graph of the effect of a solvent, such as chloroform, methyl ethyl ketone (MEK), and a mixture of MEK and hexane, on the underwater adhesion of poly(vinylcatechol-styrene) (PVCS) adhesive polymer at a concentration of 0.3 g / mL after 3 days.70938-02

[0014] FIG. IB shows the influence of the addition of solvent, e.g., various hexanes, to MEK and the effect of MEK / hexanes mixture on the underwater adhesion of PVCS adhesive polymer.

[0015] FIG. 2A shows the effect of PVCS adhesive polymer concentration in solution on underwater adhesion when the adhesive polymer was dissolved into chloroform. The consistent adhesion was observed throughout the range of adhesive polymer concentrations.

[0016] FIG 2B shows the effect of PVCS adhesive polymer concentration in solution on underwater adhesion when the adhesive polymer was dissolved into MEK. The consistent adhesion was observed throughout the range of adhesive polymer concentrations.

[0017] FIG 2C shows the effect of PVCS adhesive polymer concentration in solution on underwater adhesion when dissolved into a mixture of MEK and hexane present in the ratio of 9: 1. PVCS dissolved into the MEK / hexane (9: 1) mixture exhibited the highest adhesion values, with increased bonding at higher concentrations. The highest adhesion value of 0.73 ± 0.10 MPa was achieved with a 1.0 g / mL adhesive polymer concentration in MEK / hexanes. The adhesion value with concentrations 0.8 g / mL and 1.2 g / mL was 0.71 ± 0.08 MPa and 0.69 ± 0.07 MPa, respectively.

[0018] FIG. 3A shows graphs of viscosity versus a shear rate of PVCS solutions at concentrations of 0.3 g / mL, 0.5 g / mL, 0.8 g / mL, 1.0 g / mL, and 1.2 g / mL of PVCS dissolved into MEK / hexanes (9: 1) mixture.

[0019] FIG 3B shows graphs of viscosity versus a shear rate of polystyrene (PS) solutions at concentrations of 0.3 g / mL, 0.5 g / mL, 0.8 g / mL, 1.0 g / mL, and 1.2 g / mL of PS dissolved into MEK / hexanes (9: 1) mixture.

[0020] FIG. 3C shows the linear plot of viscosity versus the shear rate of PVCS solutions at concentrations of 0.3 g / mL, 0.5 g / mL, 0.8 g / mL, 1.0 g / mL, and 1.2 g / mL of PVCS dissolved into MEK / hexanes (9: 1) mixture.

[0021] FIG 4A shows the underwater adhesion performance of PVCS adhesive polymer upon adding calcium carbonate. The addition of 2 wt.% CaCCh resulted in a maximum underwater lap shear strength of 0.67 ± 0.07 MPa.

[0022] FIG 4B shows the underwater adhesion performance of PVCS adhesive polymer upon the addition of acrylate-butadiene rubber (ABR). The addition of 6 wt.% ABR to PVCS yielded a maximum underwater lap shear strength of 0.66 ± 0.08 MPa.

[0023] FIG. 5A shows optical microscopy and scanning electron microscopy (SEM) images of adhesive failure on coated steel surfaces of (i) PVCS alone, (ii) PVCS and 2 wt% CaCCh, and (iii) PVCS and 6 wt% ABR. The adhesive polymer that includes CaCCh or ABR, showed no fracture lines.70938-02

[0024] FIG. 5B shows the lap shear curve of PVCS adhesive polymer on coated steel bonded to polyurethane substrates.

[0025] FIG. 5C shows the lap shear curve of the adhesive polymer comprising PVCS and 2 wt% CaCCh on coated steel bonded to polyurethane substrates.

[0026] FIG. 5D shows the lap shear curve of the adhesive polymer comprising PVCS and 6 wt% ABR on coated steel bonded to polyurethane substrates.

[0027] FIG. 6A shows the lap shear curve of the adhesive polymer comprising PVCS on polished aluminum substrates bonded to polished aluminum.

[0028] FIG. 6B shows the lap shear curve of the adhesive polymer comprising PVCS and 2 wt% CaCCh on polished aluminum substrates bonded to polished aluminum.

[0029] FIG. 6C shows the lap shear curve of the adhesive polymer comprising PVCS and 6 wt% ABR on polished aluminum substrates bonded to polished aluminum.

[0030] FIG. 6D shows optical microscopy and SEM images of adhesive failure on coated steel surfaces of (i) PVCS alone, (ii) PVCS and 2 wt% CaCCh, and (iii) PVCS and 6 wt% ABR.

[0031] FIG. 7 shows an SEM micrograph of an isolated CaCCh particle from the adhesive polymer.

[0032] FIG. 8 shows the effect of water temperature on adhesion of PVCS over a time period from 1 day to 28 days at a temperature of 3 °C, 25 °C, and 60 °C.

[0033] FIG. 9 shows the graphical representation of the adhesion performance of PVCS after constant water agitation.

[0034] FIG. 10A shows the peel load versus peel displacement plots for a substrate such as etched Teflon® with the different PVCS formulations. The PVCS in MEK / hexane formulation resulted in an average peel load of 20 ± 4 N on the etched Teflon® substrate.

[0035] FIG. 10B shows the peel load versus peel displacement plots for a substrate polypropylene with the different PVCS formulations. The PVCS in MEK / hexane formulation resulted in an average peel load of 13 ± 1 N on polypropylene substrate.

[0036] FIG. 11A shows the effect of water salinity on the underwater adhesion strength of PVCS. The reduction in salinity showed a decrease in adhesion. The lap shear strength dropped from 0.71 ± 0.08 MPa to 0.50 ± 0.08 MPa as specific gravity reduced from 1.025 (seawater) to 1.012 (artificial seawater).

[0037] FIG. 11B shows the effect of pH on the underwater adhesion strength of PVCS. The highest adhesion of 0.71± 0.08 MPa was observed at a neutral pH, while adhesion decreased at both lower and higher pH levels. For example, a lap shear strength of 0.51 ± 0.01 MPa was seen for acidic conditions (pH = 5), and basic conditions yielded 0.49 ± 0.12 MPa (pH = 9).70938-02DETAILED DESCRIPTION

[0038] For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. No limitation of scope is intended by the description of these embodiments. On the contrary, this disclosure is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of this application as defined by the appended claims.

[0039] The terms "adhesive polymer," "polymer," and " adhesive" are used interchangeably.

[0040] Provided is an adhesive polymer, specifically a catechol-containing adhesive polymer, which has monomer compatibility and can be used on a large scale in industrial settings for underwater applications.

[0041] Provided is an adhesive polymer comprising (i) a poly(vinylcatechol-styrene) (PVCS) copolymer comprising a 3, 4-dihydroxy styrene monomer and a styrene monomer, (ii) an organic solvent, wherein the organic solvent is partially miscible with water and less dense than water, and (iii) optionally a filler. In embodiments thereof, the adhesive polymer consists essentially of, or consists of, (i)-(iii).

[0042] PVCS, also known as poly[(3,4-dihydroxystyrene)-co-styrene], can be represented by formula (I):PVCS comprises a 3, 4-dihydroxy styrene monomer, which is a catechol-containing monomer and a styrene monomer. Catechol and styrene monomers can exhibit high compatibility due to the structural similarity between the catechol moiety and the phenyl ring in styrene. This close resemblance can facilitate monomer copolymerization, minimizing potential disruptions to the final polymer architecture. The average molecular weight of PVCS can be about 3,00070938-02 grams / mole to about 300,000 grams / mole. The average molecular weight of PVCS can be about 5,000 grams / mole to about 250,000 grams / mole.

[0043] The 3, 4-dihydroxy styrene can comprise about 1% to about 49% of the copolymer adhesive by molar percentage. In some embodiments, the 3, 4-dihydroxy styrene can comprise about 20% to about 30% of the copolymer adhesive by molar percentage. In some embodiments, the 3, 4-dihydroxy styrene can comprise about 25% of the copolymer adhesive by molar percentage. In some embodiments, the 3, 4-dihydroxy styrene can comprise less than 25% of the copolymer adhesive by molar percentage. The unsubstituted styrene can comprise about 51% to about 99% of the copolymer adhesive by molar percentage. In some embodiments, the unsubstituted styrene can comprise about 70% to about 80% of the copolymer adhesive by molar percentage. In some embodiments, the unsubstituted styrene can comprise about 75% of the copolymer adhesive by molar percentage. In some embodiments, the unsubstituted styrene can comprise more than 75% of the copolymer adhesive by molar percentage. The percent ranges specified herein are inclusive of the stated end points.

[0044] The adhesive polymer can be used in a solution form. The adhesive polymer comprises any suitable organic solvent that is partially miscible with water and is less dense than water. The completely miscible solvent with water rapidly dissipates underwater, causing polymer precipitation since PVCS is not water-soluble. It can hinder interaction between PVCS and the substrate surface and prevent the formation of adhesive bonds.

[0045] The organic solvent, partially miscible with water and less dense than water, can be selected from the group consisting of a ketonic solvent, a hydrophobic solvent, and a mixture of ketonic and hydrophobic solvents, wherein the ketonic and hydrophobic solvents are less dense than water. The ketonic solvent can be acetone, butanone, or methyl ethyl ketone (MEK). In some embodiments, the ketonic solvent is MEK. MEK is partially miscible, less dense than water, and a good solvate for PVCS. The hydrophobic solvent can be added to reduce overall miscibility with water, which can hinder water permeation into the adhesive bond during underwater application and curing. It can improve the long-term bond strength. In some embodiments, the hydrophobic solvent is an alkane selected from hexane, cyclohexane, butane, isobutane, and pentane. Desirably, the hydrophobic solvent is hexane. In some embodiments, the organic solvent can be a mixture of MEK and hexane. MEK and hexane are industrially viable solvents and can be used on a large scale. In some embodiments, the MEK and hexane can be present in a ratio between about 8: 1 to about 15: 1. In some embodiments, MEK and hexane can be present in a ratio of about 8: 1. In some embodiments, MEK and hexane can be present in a ratio of about 9: 1. In some embodiments, MEK and hexane can be present in a ratio of about 10: 1. In some70938-02 embodiments, MEK and hexane can be present in a ratio of about 11 : 1. In some embodiments, MEK and hexane can be present in a ratio of about 12: 1. In some embodiments, MEK and hexane can be present in a ratio of about 13 : 1. In some embodiments, MEK and hexane can be present in a ratio of about 14: 1. Desirably, the ratio is about 9: 1 (such as 9: 1). The ranges specified herein are inclusive of the stated end points and specifically include all 0.1 increments within the specified ranges.

[0046] The concentration of PVCS in the organic solvent, such as a mixture of MEK and hexane(MEK / hexane, 9: 1), can be from about 0.1 g / mL to about 1.5 g / mL. In some embodiments, the concentration of PVCS in MEK / hexane can be about 0.3 g / mL. In some embodiments, the concentration of PVCS in MEK / hexane can be about 0.5 g / mL. In some embodiments, the concentration of PVCS in MEK / hexane can be about 0.8 g / mL. In some embodiments, the concentration of PVCS in MEK / hexane can be about 1.0 g / mL. In some embodiments, the concentration of PVCS in MEK / hexane can be about 1.2 g / mL. In some embodiments, the concentration of PVCS in MEK / hexane can be about 1.5 g / mL. PVCS dissolved into theMEK / hexanes (9: 1) mixture showed the highest adhesion values on a wet surface, with increased bonding at higher concentrations. The polymer concentration in a solution can be a critical parameter in adhesive development, influencing viscosity, wetting behavior, ease of application, and overall performance. The advantages of using less dense organic solvents (e.g., MEK / hexane) include the following: the polymer can provide higher adhesion at high polymer concentrations compared to the polymer comprising high dense solvents (e.g., chloroform) (Fig. 2A and Fig. 2C). It offers the polymer favorable consistency for underwater application, allowing for easy manipulation and effective adhesion to substrates with diverse shapes and geometries at higher polymer concentrations of 0.8 g / mL and above. These formulations also demonstrated minimal dripping in a vertical setting, a crucial characteristic for many practical applications.

[0047] In some embodiments, the adhesive polymer comprises a filler. Any suitable filler can be used. The filler can modify the mechanical and physical properties of the adhesive polymer. These modifications can include improved overall strength and durability, enhanced crack dissipation, distribution of mechanical stresses, increased heat resistance, and better ease of application. In some embodiments, the filler can be an inorganic filler. The inorganic filler can be selected from the group consisting of natural clay, calcium carbonate (CaCCh), zinc Oxide (ZnO), synthetic clay, and any combination thereof. In some embodiments, the inorganic filler is selected from the group consisting of Montmorillonite (MMT-K10); Montmorillonite, dimethyl dialkyl amine (MMT-DDA or MMT-amine); Montmorillonite, trimethyl stearyl ammonium (MMT-TSA or70938-02MMT-am); Laponite® RD (LRD); Laponite® XLS; ZnO, and CaCCh. Desirably, the inorganic filler is CaCCh.

[0048] In some embodiments, the filler can be a polymeric material. In some embodiments, the polymeric material is selected from the group consisting of protein, polysaccharide, rubber and any combination thereof. In some embodiments, the polymeric material is rubber. Any suitable rubber can be used. The rubber can be a natural rubber or a synthetic rubber. Examples of rubber include, but are not limited to, polyisoprene rubber (IR), polybutadiene rubber (BR), acrylated- butadiene rubber (ABR), styrene polybutadiene rubber (SBR), butyl rubber (IIR), acrylonitrile butadiene rubber (NBR), ethylene propylene diene rubber (EPDM), polychloroprene rubber (CR), chlorobutyl rubber (CIIR), bromobutyl rubber (BIIR), hydrogenated acrylonitrile butadiene rubber (HNBR), and chlorosulfonated polyethylene (CSM). In some embodiments, the rubber can be a recycled tire rubber (crumb rubber) or acrylate-butadiene rubber (ABR). In some embodiments, rubber is acrylate-butadiene rubber (ABR). It can enhance the hydrophobicity of the polymer.

[0049] In adhesive polymer, the filler can be present in a proportion of about 1 wt% of the polymer to about 30 wt % of the polymer, such as about 1 wt% of the polymer to 30 wt % of the polymer, 1 wt% of the polymer to about 30 wt % of the polymer, or 1 wt% of the polymer to 30 wt % of the polymer. In some embodiments, the filler can be present in a proportion of about 1 wt% of the polymer. In some embodiments, the filler can be present in a proportion of about 2 wt% of the polymer. In some embodiments, the filler can be present in a proportion of about 4 wt% of the polymer. In some embodiments, the filler can be present in a proportion of about 6 wt% of the polymer. In some embodiments, the filler can be present in a proportion of about 8 wt% of the polymer. In some embodiments, the filler can be present in a proportion of about 10 wt% of the polymer. In some embodiments, the filler can be present in a proportion of about 15 wt% of the polymer. In some embodiments, the filler can be present in a proportion of about 20 wt% of the polymer. In some embodiments, the CaCCh can be present in a proportion of about 2 wt% of the polymer (e.g., 2 wt% of the polymer). In some embodiments, the ABR can be present in a proportion of about 6 wt% of the polymer (e.g., 6 wt% of the polymer).

[0050] The adhesion strength of the polymer on a wet surface can be about 0.3 MPa to about 3 MPa. In some embodiments, the adhesion strength can be about 0.6 MPa. In some embodiments, the adhesion strength can be about 0.7 MPa. In some embodiments, the adhesion strength can be about 0.66 MPa. In some embodiments, the adhesion strength can be about 0.67 MPa. In some embodiments, the adhesion strength can be about 0.69 MPa. In some embodiments, the adhesion strength can be about 0.71 MPa. In some embodiments, the adhesion strength can be about 0.7370938-02MPa. In some embodiments, the adhesion strength can be about 0.8 MPa. In some embodiments, the adhesion strength can be about 0.9 MPa. In some embodiments, the adhesion strength can be about 1.1 MPa. In some embodiments, the adhesion strength can be about 1.2 MPa. In some embodiments, the adhesion strength can be about 1.3 MPa. In some embodiments, the adhesion strength can be about 1.6 MPa. In some embodiments, the adhesion strength can be about 2.0 MPa. In some embodiments, the adhesion strength can be about 2.3 MPa. In some embodiments, the adhesion strength can be about 2.6 MPa. In some embodiments, the adhesion strength can be about 3.0 MPa.

[0051] The lap shear strength of about 0.69 MPa can be achieved with a 1.2 g / mL concentration of PVCS in MEK / hexanes (9: 1). The lap shear strength of about 0.71 MPa can be achieved with a 0.8 g / mL concentration of PVCS in MEK / hexanes (9: 1). The lap shear strength of about 0.73 MPa can be achieved with a 1.0 g / mL concentration of PVCS in MEK / hexanes (9: 1).

[0052] Table 2 shows the underwater adhesion strength of the adhesive polymer. In some embodiments, the adhesive polymer has an adhesion value to etched aluminum of about 1.2 ± 0.4 (e.g., 1.2 ± 0.4) MPa. In some embodiments, the adhesive polymer has an adhesion value to steel of about 0.7 ± 0.2 (e.g., 0.7 ± 0.2) MPa. In some embodiments, the adhesive polymer has an adhesion value to coated steel of about 1.2 ± 0.1 (e.g., 1.2 ± 0.1) MPa. In some embodiments, the adhesive polymer has an adhesion value to polyurethane of about 0.1 ± 0.0 (e.g., 0.1 ± 0.00) MPa. In some embodiments, the adhesive polymer has an adhesion value to coated steel-polyurethane of about 0.7 ± 0.1 (e.g., 0.7 ± 0.1) MPa. In some embodiments, the adhesive polymer has an adhesion value to polished aluminum of about 2.3 ± 0.7 (e.g., 2.3 ± 0.7) MPa.

[0053] In some embodiments, the solid component to solvent wt.% ratio is such that substantially all of the solid components are dissolved (and remain dissolved at rest) in the solvent. In some embodiments, the solid component to solvent percent weight ratio is such that the majority of the solid components are dissolved in the solvent, albeit some solid components can remain suspended therein. It will be appreciated that the higher the wt.% of solid components of the prepared adhesive polymer prior to curing, the more viscous the solution will be. Accordingly, the wt.% ratio of solid components to solvent can be modified to achieve a particular viscosity as may be beneficial for a particular use case of the adhesive polymer.

[0054] The viscosity of the polymer can vary based on the polymer concentration. The viscosity of polymer can be increased with increasing concentration of polymer in the solvent. The adhesive polymer can exhibit a viscosity of about 0.05 Pa.s to about 10 Pa.s, such as 0.05 Pa.s to about 10 Pa.s, about 0.05 Pa.s to 10 Pa.s, or 0.05 Pa.s to 10 Pa.s.70938-02

[0055] PVCS is a copolymer prepared by polymerization of a 3, 4-dihydroxy styrene monomer and styrene monomer. In some embodiments, PVCS can be prepared using a method of radical- initiated suspension polymerization reported in Macromolecules 2023, 56, 1141-1153, which is incorporated herein by reference for its teaching regarding the same. This radical-initiated suspension polymerization can be used to synthesize PVCS on a commercial scale. In addition to the large amount of product that can be produced, radical-initiated suspension polymerization has several benefits for commercial production, including water as the primary solvent, control over polymer molecular weight, and ease of polymer cleanup. Because the monomers are kept within a micelle throughout the reaction, radical-initiated suspension polymerization results in high conversion, thus high yield and less residual monomer.

[0056] The radical-initiated suspension polymerization in water was employed to copolymerize 3, 4-dimethoxy styrene and styrene using poly(vinyl alcohol) and sodium dodecyl sulfate as stabilizing agents, and benzyl peroxide as a thermal initiator. The resulting poly(3,4- dimethoxystyrene-styrene) was demethylated using iodocyclohexane to yield poly(vinylcatechol- styrene) as a light brown powder.

[0057] Provided is a method of using the above-described adhesive polymer, which method comprises applying the adhesive polymer to at least a first substrate, which is to be adhered to at least a second substrate, and adhering the at least first substrate and the at least second substrate to each other. The method further comprises applying the adhesive polymer to the at least second substrate prior to adhering the at least first substrate and the at least second substrate.

[0058] Adhered substrates are also provided. In some embodiments, an adhered substrate can comprise a substrate comprising any of the adhesive polymers hereof applied thereto. The substrate can be exposed to dry, wet, moist, or underwater conditions. The first substrate and / or second substrate can comprise metal, wood, plastic, ceramic, polyurethane, rubber, polytetrafluoroethylene (Teflon®), polypropylene or any combination thereof. The metal substrate can be steel or aluminum. In some embodiments, the substrate can be epoxy-coated steel. In some embodiments, the substrate can be polyurethane. In some embodiments, the substrate can be etched aluminum or polished aluminum. In some embodiments, the at least first substrate and the at least second substrate are subjected to the underwater conditions prior to, subsequent to, or during adhering.

[0059] In some embodiments, when cured on the substrate, the adhesive polymer chemically bonds and / or adheres to the substrate. The adhesive polymer can be used to adhere substrates in a dry, wet, moist, or underwater environment. The substrates can be selected from metal substrates such as steel or aluminum, wood, plastic such as polyvinyl chloride (PVC), polyurethane, or70938-02Teflon®, polypropylene and any combination thereof. In some embodiments, the metal substrates are steel or aluminum. The aluminum can be polished aluminum or etched aluminum. The steel can be sanded steel or coated steel. In some embodiments, the adhesive polymer shows about six to seven-fold improved underwater adhesion strength than reported (ACS Appl Mater Interfaces 2017, 9, 7866-7872) for etched aluminum and steel. The substrates that adheres to each other can be the same or different from each other.

[0060] The adhesive polymer can have strong adhesion for coated steel-to-polyurethane bonds and aluminum. The catechol moieties within the PVCS can promote favorable interactions with metal surfaces. The adhesive polymer on an etched aluminum surface can show significantly enhanced (e.g., at least double the known adhesive) bond strength underwater. The adhesive polymer can be pressure-sensitive. The adhesive polymer was subjected to a peel test at an angle of 90 ° to evaluate its performance under various stress conditions. In some embodiments, the rigid substrate can be coated steel. In some embodiments, the flexible substrates can be Teflon® and polypropylene. In some embodiments, the peel strength of the adhesive polymer on Teflon® is about 0.8 ± 0.2 N / mm. In some embodiments, the peel strength of the adhesive polymer on polypropylene is about 0.5 ± 0.1 N / mm. The PVCS in MEK / hexane formulation resulted in an average peel load of about 20 ± 4 N on etched Teflon®. The PVCS in MEK / hexane formulation resulted in an average peel load of about 13 ± 1 N on polypropylene.

[0061] The bonding strength of the polymer underwater can be affected by the temperature of the water. The bonding strength at or about 3 °C, room temperature (RT), and 60 °C was studied after 1, 3, 7, and 28 days underwater. The bonding remained constant at RT after 1, 3, and 7 days of application, followed by a decrease of 0.15 MPa (21% decrease) after 28 days. At 3 °C, a gradual increase in adhesion strength over the first week can be observed. This behavior can be attributed to the combined effects of lower temperatures, reducing polymer chain mobility, and slowing solvent loss rates. These phenomena potentially extended the curing time of the adhesive. After 28 days, the adhesion strength achieved at 3 °C was comparable to the bonding observed at room temperature after the same period of time. Testing at an elevated temperature of 60 °C revealed a decrease in adhesion values compared to room temperature and 3 °C water, and an overall trend of decrease in adhesion over time.

[0062] The pH value of water can influence the performance of catechol-containing adhesive polymer. Catechol oxidation can be promoted at higher pH values in the presence of oxygen. Thus, the oxidative cross-linking, which is a primary adhesive mechanism of catechol-containing moieties, can be impacted by pH variations. The adhesion strength of the adhesive polymer was tested at pH values 5, 7, and 9. In some embodiments, the adhesion value at pH 7 is about 0.71 ±70938-020.08 MPa (such as 0.71 ± 0.08 MPa). In some embodiments, the adhesion value at pH 5 is about 0.51 ± 0.01 MPa (such as 0.51 ± 0.01 MPa). In some embodiments, the adhesion value at pH 9 is about 0.49 ± 0.12 MPa (such as 0.49 ± 0.12 MPa).

[0063] Advantageously, the adhesive polymer can work in a dry environment, underwater, or on moist or wet surfaces. Typical adhesives known in the art work in dry environments but do not work when applied underwater or on wet surfaces. Dry adhesives known in the art do not show strong bonding underwater or on wet surfaces. The adhesive polymer can be used in any kind of water, such as fresh water or salt water. The substrates can be submerged underwater during the application of the polymer adhesive or after the application. It is hypothesized that the potential chemical interactions between the adhesive and water - which are not present in dry bonding - increase the importance of intra-adhesive surface attachment relative to dry bonding and result in an optimized wet bonding adhesive, which differs significantly in catechol content and molecular weight from the optimized dry bonding adhesive.

[0064] It will nevertheless be understood that no limitation of the scope of this disclosure is thereby intended. Any alterations and further modifications of the described or illustrated embodiments and any further applications of the principles of the invention as illustrated herein are contemplated as would normally occur to one skilled in the art to which the invention relates. At least one embodiment of the invention is shown in great detail, although it will be apparent to those skilled in the relevant art that some features or some combinations of features may not be shown for the sake of clarity.EXAMPLESThe following experimental section serves to illustrate the present disclosure. The experimental section is not intended to limit the scope of the claimed invention in any way.Materials

[0065] Solvents were purchased from Sigma-Aldrich or Fisher Scientific and used without additional purification. Calcium carbonate (Vicron® 15-15) with an average particle size of 3.5 pm was used. Recycled tire rubber, ABR mesh size 80-99, was obtained from Entech, Inc. (Middlebury, IN).Example-1: Polymer synthesis70938-02

[0066] Poly(vinylcatechol-styrene) was synthesized following a method reported in Macromolecules 2023, 56, 1141-1153, which is specifically incorporated herein by reference for its teaching regarding the same. A radical-initiated suspension copolymerization in water was employed to copolymerize 3, 4-dimethoxy styrene and styrene using poly(vinyl alcohol) and sodium dodecyl sulfate as stabilizing agents, and benzyl peroxide as thermal initiator. The resulting poly(3,4-dimethoxystyrene-styrene) was demethylated using iodocyclohexane to yield poly(vinylcatechol-styrene) as a light brown powder.‘HNMR (CDCh, 300 MHz): 8 (ppm) 7.07 (m, 2.28H, 3HAr-styr), 6.58 (m, 1.76H, 2HAr-styr+ IHAT- cat), 6.00 (m, 0.48H, 2HAr-cat), 1.78 (m, 1H, -CHPh-CH2-), 1.44 (m, 2H, -CHPh-CH2-). Average molecular weight (Mn): 39.4kDa. The weight average molecular weight (Mw): 156.2 kDa.Example-2: Substrate preparation

[0067] Steel panels HR SP5 (12” x 6” x 1 / 8” and 4” x 1” x 1 / 8”) were coated with a 2-part epoxy coating, Hycote 151. Steel substrates were coated to prevent corrosion in aqueous environments. Epoxy organic coatings effectively address this challenge, offering exceptional adhesion to steel, superior chemical resistance, and ease of application. Polyurethane sheets (1” x 24” x 24” and 1 / 4" x 24” x 24”) cut into 2” x 1” x 1” and 2” x 1” x 1 / 4” pieces using a 10” Saw Stop Table Saw with a Diablo 10” 90 teeth saw blade. Three ft. long 6061 aluminum sheets (1 / 8" x 1 / 2") cut into 3.5” long pieces. Aluminum substrates were polished using a buffing wheel with a sequence of Tripoli brown buffing compound followed by a green buffing compound. Subsequently, the substrates underwent solvent cleaning with hexanes, acetone, methanol, and water. Etching of aluminum substrates was performed following the ASTM D2651 method, utilizing boiling base and acid baths, followed by cleaning steps in methanol and boiling water. Etched Teflon® (48” x 24” x 0.02”) and polypropylene (45” x 24” x 0.02”) sheets were cut into 7” x 1” strips using a paper trimmer.Example-3: Water preparation

[0068] Adhesion experiments were set up in artificial seawater prepared at least 24 hours prior with a specific gravity of 1.025, using Marine Environment® dual-phase formula.Example-4: Lap shear adhesion testing

[0069] Lap shear bonding was employed for all adhesion tests in this disclosure, and each experiment utilized seven replicate samples. For coated steel bonded to polyurethane, seven 0.5” x 1” rectangles were marked on 12” x 6” x 1 / 8” coated plates. The coated steel surfaces were lightly sanded with 80 grit aluminum oxide abrasive paper and cleaned with butyl alcohol before submersion in artificial seawater. The designated adhesive, either a formulated solution or commercial glue, was applied to the submerged steel in the marked 0.5” x 1” area. Individual 2”70938-02 x 1” x 1” polyurethane pieces, also submerged, were then bonded to the marked areas to achieve bonding underwater. Coated steel to coated steel (4” x 1” x 1 / 8”) and polyurethane to polyurethane (2” x 1” x 1 / 4”) bonding followed the same procedure with the same overlap area. Aluminum substrates (3.5” x 1 / 8” x 0.5”) utilized a modified version of the ASTM D1002 standard for lap shear bonding, with a 0.5” x 0.5” overlap area. In most cases, a 20 g dead weight was applied on top of the adhesive joints to aid curing. Unless otherwise stated, all samples were cured underwater for 3 days. Following underwater curing, samples were removed from the artificial seawater and tested in tension using an Instron 5544 materials testing system equipped with a 2 kN load cell. Each sample was subjected to a constant crosshead speed of 2 mm / min until failure. The maximum force required to break the bond was recorded. Lap shear strength was determined by dividing the maximum force by the bonded overlap area for each sample. The data were subsequently averaged and the error bars represent 90% confidence intervals.Example-5: Water content analysis

[0070] Following lap shear testing, the persistent water content of the adhesives was quantified usingJH nuclear magnetic resonance spectroscopy (NMR). Deuterated chloroform was the reference solvent.Example-6: Viscosity experiments

[0071] Rheological properties of poly(vinylcatechol-styrene) solutions at various concentrations were investigated using a rheometer. Control experiments were performed on polystyrene samples (average Mw = 90,000 g / mol) at corresponding concentrations. Viscosity measurements were obtained using a Peltier recessed concentric cylinder geometry at a constant temperature of 25 °C. A solvent trap was employed throughout the experiments to minimize solvent evaporation. Triplicate measurements were conducted at each concentration with a shear rate sweep from 0.01 to 100 s’1, recording five data points per decade.Example-7: Imaging

[0072] Failed bond surfaces were characterized using optical microscopy and scanning electron microscopy. Optical images were acquired using an Olympus BX-51 Optical Microscope. High- resolution micrographs of the fracture surfaces were obtained using a Quanta 3D FEG dual-beam electron microscope.Example-8: Water temperature range study

[0073] For room temperature experiments, joints were set up in the laboratory without further temperature modification. For experiments at 3 °C, artificial seawater was cooled down in a refrigerator set to 3 °C and verified with a thermometer. After reaching the desired temperature, seawater was removed from the refrigerator, experiments were set up immediately, and samples70938-02 were returned to the refrigerator until testing. For experiments at 60 °C, seawater was heated using an Anova Culinary Sous Vide Precision Cooker Nano 3.0 and maintained at that temperature until testing.Example-9: Contact angle goniometry

[0074] Contact angle measurements were conducted using an optical tensiometer. For each measurement, a 3 pL droplet of deionized water was deposited onto the substrate using a micropipette, and the tensiometer captured images of the droplet at video rates. The images were subsequently analyzed with the software in sessile droplet mode, employing the Young-Laplace equation. Each contact angle measurement is based on the average of 152 data points, with four measurements taken on each sample. Reported errors correspond to one standard deviation.Example-10: 90° Peel Testing

[0075] Coated steel substrates (6” x 2” x 1 / 8”) were lightly sanded with 80-grit aluminum oxide abrasive paper, cleaned with butyl alcohol, and submerged under artificial seawater. Adhesive formulations were then applied to a 5” x 1” area of etched Teflon® or polypropylene strips (7” x 1” x 0.02”) in air and bonded to the submerged coated steel substrates. A 2” section of the flexible adherend was left unbonded. A 380 g weight was placed on top of the strips while the adhesive cured underwater for 7 days. Four samples were prepared for each adhesive formulation and flexible substrate type. After curing, the specimens were removed from the water and placed into the 90° peel test fixture of an Instron® 3340TM-30 testing machine equipped with a 2 kN load cell. The unbonded 2” end of the flexible adherend was bent perpendicular to the steel substrate and clamped into the grip. The samples were then peeled at a constant crosshead speed of 254 mm / min, following the ASTM 6862 standard.

[0076] Results:

[0077] Solvent selectionThe reported underwater work with PVCS adhesives used chloroform as the solvent of choice, given its ability to prevent polymer precipitation during underwater application due to its high density and immiscibility with water (ACS Appl Mater Interfaces, 2017, 9, 7866-7872). However, toxicity associated with chloroform poses an obstacle to commercialization. This challenge was addressed by exploring alternative solvents that maintain the desired adhesive properties of PVCS while prioritizing industrial viability. To facilitate initial investigations and ensure consistency with established protocols for underwater adhesive applications, a PVCS concentration of 0.3 g / mL was selected in the chosen solvent.70938-02

[0078] Acetone was initially explored due to its good solubility for PVCS. However, the complete miscibility of acetone with water led to rapid dissipation underwater. Since PVCS is not water- soluble, polymer precipitation was observed upon acetone dissipation. The interaction between PVCS and the substrate surface was hindered, preventing the formation of adhesive bonds. Methyl ethyl ketone (MEK) was explored as a potential replacement due to similar properties and good solvating abilities for PVCS. Unlike the complete miscibility of acetone with water, MEK exhibits only partial water compatibility. This partial miscibility of MEK allowed for some water ingress into the adhesive bond during the curing process. This water presence, observed at the interface of the substrates following mechanical testing, could compromise the long-term bond strength of the PVCS adhesive. This issue was addressed by the minor addition of a hydrophobic solvent, such as hexanes, to the MEK solution. The addition of hexanes reduced the overall miscibility with water, thereby hindering water permeation into the adhesive bond during underwater application and curing. This strategy did not impact the performance of the PVCS adhesive (FIG. 1A). An investigation was conducted to determine the optimal hexanes concentration, revealing that a 9: 1 v / v MEK / hexanes ratio yielded the most favorable results (FIG. IB)

[0079] To quantify water content within the adhesive bonds, samples were analyzed through 'H NMR spectroscopy after lap shear testing. Two distinct sample preparation methods were employed. First, an immediate test was designed so that samples were retrieved directly from the underwater environment and subjected to lap shear testing without any drying step. This approach captured the entire adhesive layer, including any interfacial water, for subsequent analysis. A second test was carried out by retrieving samples from the underwater environment and allowing them to dry for one hour under ambient conditions before lap shear testing. The adhesive polymer was then isolated for 'H NMR analysis, excluding any residual water at the interface. Data obtained from the 'H NMR analyses are summarized in Table 1. Table 1 presents the initial molar composition of PVCS and the corresponding solvents used in the formulations, as well as the molar ratios of PVCS, solvent, and water measured after both the immediate test and dried test for each sample.

[0080] Analysis of samples retrieved immediately after testing revealed a significant influence of solvent selection on water uptake into the adhesive interface. Samples prepared with the MEK / hexane mixture exhibited a 29% reduction in water content compared to those dissolved in solely MEK. Samples prepared with chloroform displayed the lowest interfacial water content. This observation can be attributed to the inherent hydrophobicity of chloroform, which minimized water permeation into the adhesive. Samples allowed to dry for one hour before testing showed70938-02 similar water content across all solvent formulations. This result suggests that the permeation of water within the inner part of the adhesive bulk was similar regardless of the initial solvent composition. Based on the combined analysis of these results and the adhesion performance of the formulations, a MEK / hexanes (9: 1) solvent system was selected for use in subsequent studies.

[0081] Table 1. H NMR analysis of water content in adhesive samples using different solvents.

[0082] Polymer concentrationThe polymer concentration in solution is a critical parameter in adhesive development, influencing viscosity, wetting behavior, ease of application, and ultimately, overall performance. These factors become particularly important for an adhesive that specializes in underwater bonding. It was observed that 0.3 g / mL solution consistency was thin and rolled away, potentially hindering application in quotidian scenarios. To address this challenge, investigated the underwater adhesion performance of PVCS solutions at various concentrations, ranging from 0.3 g / mL to the solubility limit of 1.2 g / mL, across the three studied formulations, i.e., PVCS dissolved into chloroform, MEK, and MEK / hexanes (9: 1). This study strived to optimize underwater adhesion strength while minimizing required polymer content and ensuring user- friendly application.70938-02

[0083] FIGs. 2A-2C shows lap shear adhesion strength as a function of polymer concentration in solution for the three different solvents. Bonding of PVCS dissolved into chloroform (FIG. 2A) and MEK (FIG. 2A) exhibited similar trends, with consistent adhesion observed throughout the range of concentrations. PVCS dissolved into the MEK / hexanes (9:1) mixture exhibited the highest adhesion values, with increased bonding at higher concentrations (FIG. 2C). Solutions at 0.8 g / mL and above displayed favorable consistency for underwater application, allowing for easy manipulation and adhesion to substrates with diverse shapes and geometries. These formulations also demonstrated minimal dripping in a vertical setting, a crucial characteristic for many practical applications. The highest lap shear strength of 0.73 MPa was achieved with a 1.0 g / mL concentration in MEK / hexanes, although a 95% confidence ANOVA revealed no statistically significant difference in adhesion performance between 0.8, 1.0, and 1.2 g / mL concentrations, respectively 0.71 MPa, 0.73 MPa, and 0.69 MPa. In order to prioritize both adhesion strength and material efficiency, a concentration of 0.8 g / mL was selected for further studies due to effectiveness and reduced polymer requirement. The substrate used was coated steel or polyurethane.

[0084] Viscosity studiesTo elucidate the handling properties, viscosity experiments were performed on PVCS solutions at varying concentrations prepared in 9: 1 MEK / hexanes mixtures. Flow curves for the solutions are presented in (FIG. 3A). A clear progressive increase in viscosity with increasing concentration was observed. Solutions at 0.3 and 0.5 g / mL displayed shear-independent viscosity behavior across the range of shear rates investigated. Solutions at concentrations ranging from 0.8 g / mL to 1.2 g / mL exhibited moderate shear thinning tendencies, evident by decreases in viscosity at higher shear rates, characteristic of non-Newtonian fluids. The shear thinning behavior was better visualized in the linear plots (FIG. 3C). For comparison purposes, control experiments were conducted using commercially available polystyrene (PS) - i.e., no catechol - dissolved in the same solvent mixture at equivalent concentrations. The corresponding flow curves are shown in (FIG. 3b) These PS solutions displayed a similar trend of increasing viscosity with concentration compared to PVCS solutions. However, PS solutions consistently exhibited lower viscosities than PVCS solutions at corresponding concentrations. The polymers possess differing molecular weights. The average molecular weight of PVCS was approximately 160 kDa, whereas the commercially obtained PS had an average molecular weight of 90 kDa. Previous literature reports demonstrated that increasing the molecular weight of polystyrene resulted in higher viscosity values at the investigated shear rates. Moreover, intra- and intermolecular interactions, such as hydrogen bonding between catechol’s hydroxyl groups, are70938-02 known to promote chain entanglements, significantly impacting viscosity. Consequently, PS solutions may exhibit lower viscosity values at identical shear rates compared to PVCS at equivalent molecular weights. Considering these factors, the behavior of PVCS solutions relative to PS solutions fell within an expected range. These findings corroborate the positive correlation between solution concentration and viscosity. The observed shear-thinning behavior at elevated shear stresses suggests potential improvements in adhesive handling while also reducing dripping and sagging when not being manipulated (i.e., at lower shear rates), compared to lower- concentration formulations.

[0085] FillersFillers are incorporated into adhesives to modify both mechanical and physical properties. These modifications can improve overall strength and durability, enhance crack dissipation, distribution of mechanical stresses, increase heat resistance, and better ease of application. Additionally, fillers offer an economic benefit by reducing the overall cost of adhesive formulations. Inorganic fillers, such as calcium carbonate particles, and polymeric fillers, like rubber powders, are commonly used in the industrial design and production of adhesives. The earlier study showed increased dry adhesion of a catechol-containing polymer from 4 to 5 MPa in aluminum substrates by adding calcium carbonate (ACS Sustain Chem Eng 2019, 7, 13315-13323). Nanometer-scale particles require surface modification, often via coating with stearic acid, to prevent agglomeration and maintain particle size. However, this modification may hinder polymer-filler interactions and reduce overall adhesion. Polish Journal of Chemical Technology 2015, 17, 41- 47 reported 180% increase in adhesion of plywood by adding 13 wt.% waste rubber powder to a melamine urea formaldehyde glue. The effect of incorporating 3.5 pm CaCCh and recycled tire rubber (ABR) at loadings of 1-20 wt.% into PVCS formulations was investigated. The addition of 2 wt.% CaCCh resulted in a mild maximum underwater lap shear strength of 0.67 ± 0.07 MPa (FIG. 4A). Statistical analysis of variance revealed no significant change to adhesion for the unfilled polymer at the 95% confidence level. However, it may be relevant to consider that the hydrophilic character of calcium carbonate could promote water migration into the adhesive over extended periods. This potential water ingress might weaken bonds over time. Consequently, the addition of ABR was examined. The presence of 6 wt.% ABR to PVCS yielded a maximum lap shear strength of 0.66 MPa (FIG. 4B). The filler changes to adhesion were not statistically significant. Perhaps ABR can enhance overall hydrophobicity of the polymer system.

[0086] Scanning electron microscopy (SEM) and optical microscopy images were taken on substrates after lap shear testing fail to investigate the influence of fillers on the mechanical behavior of PVCS. Coated steel-to-polyurethane specimens exhibited adhesive failure, with all70938-02 of the polymeric material remaining on the steel substrate. Control experiments were conducted with the optimized PVCS formulation, alongside those formulated with the fillers that achieved the highest adhesion values, i.e., PVCS + 2 wt.% CaCCh and PVCS + 6 wt.% ABR.

[0087] Brittle fracture characteristics were evident in the coated steel to polyurethane adhesive joints (FIG. 5A). Force-extension plots displayed sharp curves, also indicative of brittle behavior (FIGs. 5B-5D). Additionally, optical micrographs (FIG. 5A) revealed cracks within the adhesive surface. The SEM micrographs of PVCS alone also identified the presence of stress lines, corroborating the brittle fracture mechanism. The SEM analysis did not show CaCCh or ABR particles within the superficial adhesive layer (FIG. 5A), but ABR particles were detectable by optical microscopy. These particles were likely coated by the polymer matrix, suggesting minimal influence on the adhesive-substrate failure at the interface. Due to small sizes falling below the resolution limit, CaCCh particles were not observed in optical microscopy. The absence of CaCCh observed in SEM micrographs further indicated a lack of major presence at the surface, similar to the ABR particles.

[0088] To contrast the behavior of the fillers under regimes dominated by strong adhesive versus cohesive forces, cohesive failure was induced by repeating the experiments using polished aluminum substrates. Bonded polished aluminum adherends exhibited ductile cohesive failure. This behavior was reflected in the force-versus-extension curves, which displayed a less sudden break as well as higher area-under-the-curve (i.e., work of adhesion) and extension values compared to the coated steel -to-polyurethane joints (FIGs. 6A-C). A textured structure of the polymer matrix was seen, with stretching in the direction of pulling (Fig. 6D). These micrographs further supported the cohesive and ductile nature of the failure mode on aluminum. The SEM images revealed CaCCh particles dispersed within the various layers of the polymer matrix. For a control, SEM was performed on isolated particles, without any polymer, to confirm the identity to be CaCCh (FIG. 7). The ABR particles were predominantly located on the adhesive surface while also exhibiting a thin layer of PVCS coated on top. The disparity in particle behavior and distribution may be attributed to the size difference between fillers. The average particle size of 3.5 pm for CaCCh may have enabled sufficient mobility during testing to become embedded in the different layers of the polymer matrix while the force was exerted during testing. In contrast, the larger ABR particles (150-175 pm) might have experienced hindered movement. Differences in particle surface energies may also have influenced behavior.

[0089] Benchmarks and adhesion in different substrates saltwater adhesionTo establish a baseline for the underwater adhesion performance of the preferred PVCS formulation (i.e., PVCS dissolved into a mixture of MEK / hexanes (9: 1) at a concentration of 0.870938-02 g / mL), commercially available adhesives with diverse chemistries were evaluated for abilities to bond coated steel and polyurethane underwater. A selection encompassing established adhesive technologies was chosen, including a two-part epoxy specifically formulated for underwater use (Mr. Sticky's), a solvent-free, rubberized waterproof adhesive (Flex Glue), a water-activated polyurethane adhesive (Gorilla Glue), and a cyanoacrylate adhesive (Super Glue) representing a well-understood and widely used adhesive chemistry. Adhesion tests were conducted on bonds between substrates such as coated steel-to-coated steel, polyurethane-to-polyurethane, and also uncoated steel -to-uncoated steel. Aluminum substrates were also examined, given the common use of this material in different industrial applications. Etched aluminum and polished aluminum were further included in order to have a better understanding of different surface types and finishes.

[0090] Table 2 shows the underwater adhesion performance of PVCS across different substrates compared to commercial glues. Among the five adhesives evaluated, the PVCS-based formulation displayed the strongest adhesion for coated steel-to-polyurethane bonds. Mr. Sticky's surpassed all adhesives, including PVCS, when bonding steel and coated steel substrates. These results align with the well-known strength of epoxy adhesives within the spectrum of adhesive chemistries. Bonding low surface energy substrates like polyurethane poses a challenge for many or all adhesives, evidenced here by the low comparable performance observed across the commercially available options and the PVCS formulation. In contrast, the PVCS-based adhesive exhibited exceptional adhesion strength on both polished and etched aluminum. This superior performance compared to commercially available adhesives likely stems from the presence of unique catechol moieties within the PVCS polymer. These functional groups are known to promote favorable interactions with metal surfaces. Furthermore, the significantly enhanced bonding strength observed for etched aluminum, at least double that of other adhesives, suggests a contribution from mechanical interlocking between the PVCS adhesive and roughened topography of the etched surface.Table 1Underwater adhesion strength of PVCS compared to commercial glues on different substrates.70938-02

[0091] Temperature range studyTo reflect the potential versatility of PVCS adhesives in various environments, the underwater adhesion performance was evaluated under a range of conditions. The bonding strengths of the optimized PVCS formulation was studied under three distinct water temperatures: 3 °C, room temperature (about 25 °C), and 60 °C. Water at 3 °C mimicked deep ocean environments, and 60 °C water served as approximating conditions encountered in pipes within oil rigs and production facilities. The lap shear strength was assessed after 1, 3, 7, and 28 days underwater. This selection reflected the potential for weakened adhesion over time due to degradation of the adhesive and increased water absorption at the joint. Furthermore, this approach aligns with understanding how polymeric materials in service environments may be subjected to diverse environmental factors. Elevated temperatures are a critical parameter for predicting polymer aging. Concerns in such scenarios can include potential solvent loss over time as well as the proximity of the operating temperature to the glass transition temperature (Tg) of the polymer, which can impact mechanical performance. The reported Tg of PVCS is approximately 120 °C.

[0092] FIG. 8 shows results from the temperature range study. At room temperature, adhesion remained constant after 1, 3 and 7 days of application, followed by a decrease of 0.15 MPa (21% decrease) after 28 days. This trend suggested good initial bond formation followed by potential slow degradation processes at longer time scales. Specimens tested at 3 °C exhibited a gradual increase in adhesion strength over the first week. This behavior may be attributed to the combined effects of lower temperatures, reducing polymer chain mobility, and slowing solvent loss rates. These phenomena potentially extended the curing time of the adhesive. After 28 days, the adhesion strength achieved at 3 °C was comparable to the bonding observed at room temperature after the same period of time. Testing at an elevated temperature of 60 °C revealed a decrease in adhesion values compared to room temperature and 3 °C water, and an overall trend of decrease in adhesion over time. While the reported glass transition temperature Tg of PVCS is twice the evaluation temperature, the higher temperature might have enhanced the mobility of polymer chains, potentially hindering their ability to form strong interfacial interactions. Furthermore, the adhesion strength of the PVCS formulation at 60 °C decreased from 0.62 ± 0.11 MPa at 1 day to 0.34 ± 0.02 MPa after one month, potentially due to the initiation of oxidation or thermal decomposition of the polymer at prolonged high temperatures. Nonetheless, the ability of PVCS70938-02 to form quantifiable, durable bonds for four weeks under what can be considered harsh conditions (under artificial seawater, and at 60 °C) remains remarkable. These results illustrate the relevance of considering both temperature and immersion time for optimizing the underwater adhesion performance of adhesives for various applications.

[0093] Moving water study

[0094] Real-world underwater environments often experience dynamic water movement due to currents, waves, or tidal forces. Applying adhesives to such surfaces does not always benefit from immobile substrates. A simplified experiment was designed to simulate these conditions and assess the performance of the optimized adhesive. In this experiment, samples were bonded underwater while the water container was placed on an orbital shaker set at 50 revolutions per minute to replicate the effects of dynamic water movement. No weights were placed on top of the samples during this test. While a decrease in adhesion strength was anticipated due to less precise placement, water movement, and an absence of curing weights, the observed decrease was less than 30% compared to the values obtained in still water after up to 1 week of curing (FIG. 8) seen here in FIG. 9. This result suggests promising potential for uses of PVCS in dynamic underwater environments.

[0095] Salinity and pHSalinity and pH are also important factors to consider when bonding substrates underwater. Potential applications of PVCS could extend to brackish waters, which have lower salinity than seawater but higher than fresh water. To investigate the impact of reduced salinity on adhesion performance, water salinity was decreased in adhesion studies from a specific gravity of 1.025, typical for seawater, to 1.012, common for brackish waters. This reduction in salinity resulted in a decrease in adhesion, with lap shear strength dropping to 0.50 ± 0.08 MPa, compared to 0.71 ± 0.08 MPa in specific gravity 1.025 artificial seawater (FIG. HA). These findings align with previous reports showing a decrease in adhesion when using deionized water instead of artificial seawater (salinity = 35 g / L).Similarly, water pH values may influence the performance of catechol-containing adhesives. Catechol oxidation is promoted at higher pH values in the presence of oxygen. Conversely, this moiety becomes less reactive under more acidic conditions (Desalination 2020, 491, 114445). Oxidative cross-linking, a primary adhesive mechanism in catecholic species (Chem Soc Rev 2014, 43, 8271-9888), may therefore be impacted by pH variations, affecting the adhesive performance of poly(vinylcatechol-styrene). FIG. 11B shows the lap shear strength of the optimized formulation cured in waters at pH values of 5, 7, and 9. The highest adhesion was observed at neutral pH (0.71 ± 0.08 MPa), while adhesion decreased at both lower and higher pH70938-02 levels. Specifically, a lap shear strength of 0.51 ± 0.01 MPa was seen for acidic conditions (pH = 5) and basic conditions yielded 0.49 ± 0.12 MPa (pH = 9).

[0096] 90° Peel Tests

[0097] Joints are often subjected to a variety of mechanical stresses, particularly in underwater environments. To evaluate the performance of PVCS under different stress conditions, 90° peel tests were conducted. Coated steel was used for the rigid substrate. Etched Teflon® and polypropylene provided the complementary flexible adherends. The adhesive was applied underwater between coated steel and Teflon® or coated steel and polypropylene. Joints were cured for seven days before 90° peel testing. Bonding used both the control formulation (PVCS dissolved in chloroform at 0.3 g / mL) and the optimized formulation (PVCS dissolved in MEK / hexanes (9: 1) at 0.8 g / mL). Table 3 presents the average peel loads, peel strengths, and maximum loads. The optimized formulation demonstrated superior peel strength compared to the 0.3 g / mL PVCS in chloroform formulation. Peel strengths were greater when etched Teflon® was used for the flexible adherend, as compared to polypropylene, likely due to the scuffed texture of the etched Teflon® substrate, which facilitated adhesive bonding. When using the optimized formulation on etched Teflon®, the peel strength was 0.8 ± 0.2 N / mm, compared to 0.5 ± 0.1 N / mm with the control formulation. In contrast, when polypropylene was used for the flexible adherend with the MEK / hexanes (9: 1) formulation, the peel strength was 0.5 ± 0.1 N / mm, compared to 0.3 ± 0.1 N / mm for the chloroform formulation. FIG. 10A-B presents the peel load versus displacement plots for both substrates (etched Teflon®, FIG. 10A; and polypropylene, FIG. 10B) with the different formulations. The PVCS in MEK / hexanes formulation resulted in an average peel load of 20 ± 4 N on etched Teflon® and 13 ± 1 N on polypropylene. In comparison, the PVCS in chloroform formulation yielded average peel loads of 13 ± 3 N and 8 ± 1 N for Teflon® and polypropylene, respectively. Visual inspection revealed that polypropylene substrates exhibited wrinkling and swelling after seven days of exposure to the chloroform-based adhesive formulation.Table 2. 90° peel test results for PVCS formulations on different substrates.70938-02Enumerated Embodiments:The following list of enumerated embodiments presents claims with multiply dependent claims depending from multiply dependent claims for presentation in those jurisdictions where such dependencies are allowed as well as additional claims, which may be pursued during the examination of the application or a divisional thereof.

[0098] EE1. An adhesive polymer comprising (i) a poly(vinylcatechol-styrene) (PVCS) copolymer comprising a 3, 4-dihydroxy styrene monomer and a styrene monomer, (ii) an organic solvent, wherein the organic solvent is partially miscible with water and is less dense than water, and (iii) optionally a filler.EE2. The adhesive polymer of EE1, wherein the PVCS is present in a concentration at or about 0.1 g / mL- 1.5 g / mL of the polymer.EE3. The adhesive polymer of EE1, wherein the filler is an inorganic filler.EE4. The adhesive polymer of EE3, wherein the inorganic filler is selected from the group consisting of natural clay, calcium carbonate (CaCCh), zinc oxide (ZnO), synthetic clay, and a combination of two or more thereof.EE5. The adhesive polymer of EE3, wherein the inorganic filler is CaCCh.EE6. The adhesive polymer of EE1, wherein the filler is a polymeric material.EE7. The adhesive polymer of EE6, wherein the polymeric material is selected from the group consisting of protein, polysaccharide, rubber and any combination thereof.EE8. The adhesive polymer of EE7, wherein the rubber is recycled tire rubber (crumb rubber) or acrylate-butadiene rubber (ABR).70938-02EE9. The adhesive polymer of any one of EE3-EE8, wherein the inorganic filler is present at about 1 wt% to about 20 wt% of the adhesive polymer.EE10. The adhesive polymer of EE1, wherein the organic solvent is selected from a ketone, a hydrophobic solvent and a mixture of a ketone and a hydrophobic solvent.EE11. The adhesive polymer of EE10, wherein the ketone is acetone, butanone or methyl ethyl ketone.EE12. The adhesive polymer of EE10, wherein the hydrophobic solvent is hexane, cyclohexane, butane, isobutane, or pentane.EE13. The adhesive polymer of any one of EE10-EE12, wherein the organic solvent is a mixture of methyl ethyl ketone and hexane in a ratio of about 6: 1 to about 15: 1.EE14. The adhesive polymer of EE13, wherein the methyl ethyl ketone and hexane are in a ratio of about 9: 1.EE15. The adhesive polymer of EE1, wherein the adhesive polymer exhibits an adhesion on a wet surface from about 0.5 MPa to about 3 MPa.EE16. The adhesive polymer of EE1, wherein the adhesive polymer has a viscosity of about 0.05 Pa.s to about 10 Pa.s.EE17. The adhesive polymer of EE1, wherein the adhesive polymer has a wet peel strength of about 0.4 N / mm to about 1 N / mm at a peel angle of 90 °.EE18. A method of using the adhesive polymer of EE1, which method comprises applying the adhesive polymer to at least a first substrate, which is to be adhered to at least a second substrate, and adhering the at least first substrate and the at least second substrate to each other such that the adhesive polymer is sandwiched therebetween.EE19. The method of EE18, which further comprises applying the adhesive composition to the at least second substrate prior to adhering the at least first substrate and the at least second substrate.70938-02EE20. The method of EE18 or EE19, wherein the at least first substrate and / or the at least second substrate are exposed to moist, wet, or underwater conditions.EE21. The method of EE18 or EE19, wherein the at least first substrate and / or the at least second substrate is metal, wood, plastic, rubber, polyurethane, Teflon®, polypropylene or a combination of two or more of the foregoing.EE22. The method of EE21, wherein the metal is steel or aluminum.

[0099] As used herein, the following terms and phrases shall have the meanings set forth below. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art.

[0100] The term "about" can allow for a degree of variability in a value or range, for example, within 10%, within 5%, or within 1% of a stated value or of a stated limit of a range.

[0101] The term "substantially" can allow for a degree of variability in a value or range, for example, within 90%, within 95%, or within 99% or within 99.5%, 99.9%, 99.99%, or 99.999% or more of a stated value or of a stated limit of a range, inclusive of the specified end points.

[0102] The terms "a," "an," or "the" are used to include one or more than one unless the context clearly dictates otherwise. The term "or" is used to refer to a nonexclusive "or" unless otherwise indicated. In addition, the phraseology or terminology employed herein, and not otherwise defined, is for the purpose of description only and not of limitation. Any use of section headings is intended to aid reading of the document and is not to be interpreted as limiting. Further, information that is relevant to a section heading may occur within or outside of that particular section. The terms "including" and "having" are defined as comprising (i.e., open language).

[0103] The disclosure may be suitably practiced in the absence of any element(s) or limitation(s), which is / are not specifically disclosed herein. Thus, for example, each instance herein of any of the terms “comprising,” “consisting essentially of,” and “consisting of’ (and related terms such as “comprise” or “comprises” or “having” or “including”) can be replaced with the other mentioned terms.

[0104] When ranges are used herein for physical properties, such as weight percentages, or chemical properties, such as chemical formulae, all combinations and sub-combinations of ranges and specific embodiments therein are intended to be included.70938-02

[0105] Those skilled in the art will recognize that numerous modifications can be made to the specific implementations described above. The implementations should not be limited to the particular limitations described. Other implementations may be possible.

[0106] It is intended that the scope of the present methods and apparatuses be defined by the following claims. However, it must be understood that this disclosure may be practiced otherwise than is specifically explained and illustrated without departing from its spirit or scope. It should be understood by those skilled in the art that various alternatives to the embodiments described herein may be employed in practicing the claims without departing from the spirit and scope as defined in the following claims.

[0107] All patents, patent application publications, journal articles, textbooks, and other publications mentioned in the specification are indicative of the level of skill of those in the art to which the disclosure pertains.

Claims

70938-02WHAT IS CLAIMED IS:

1. An adhesive polymer comprising (i) a poly(vinylcatechol-styrene) (PVCS) copolymer comprising a 3, 4-dihydroxy styrene monomer and a styrene monomer, (ii) an organic solvent, wherein the organic solvent is partially miscible with water and is less dense than water, and (iii) optionally a filler.

2. The adhesive polymer of claim 1, wherein the PVCS is present in a concentration at or about 0.1 g / mL- 1.5 g / mL of the polymer.

3. The adhesive polymer of claim 1, wherein the filler is an inorganic filler.

4. The adhesive polymer of claim 3, wherein the inorganic filler is selected from the group consisting of natural clay, calcium carbonate (CaCCh), zinc oxide (ZnO), synthetic clay, and a combination of two or more thereof.

5. The adhesive polymer of claim 3, wherein the inorganic filler is CaCCh.

6. The adhesive polymer of claim 1, wherein the filler is a polymeric material.

7. The adhesive polymer of claim 6, wherein the polymeric material is selected from the group consisting of protein, polysaccharide, rubber and any combination thereof.

8. The adhesive polymer of claim 7, wherein the rubber is recycled tire rubber (crumb rubber) or acrylate-butadiene rubber (ABR).

9. The adhesive polymer of any one of claims 3-8, wherein the filler is present at or about 1 wt% - 20 wt% of the adhesive polymer.

10. The adhesive polymer of claim 1, wherein the organic solvent is selected from a ketone, a hydrophobic solvent and a mixture of a ketone and a hydrophobic solvent.

11. The adhesive polymer of claim 10, wherein the ketone is acetone, butanone or methyl ethyl ketone.70938-0212. The adhesive polymer of claim 10, wherein the hydrophobic solvent is hexane, cyclohexane, butane, isobutane, or pentane.

13. The adhesive polymer of any one of claims 10-12, wherein the organic solvent is a mixture of methyl ethyl ketone and hexane in a ratio of about 6: 1 to about 15: 1.

14. The adhesive polymer of claim 13, wherein the methyl ethyl ketone and hexane are in a ratio of about 9: 1.

15. The adhesive polymer of claim 1, wherein the adhesive polymer exhibits an adhesion on a wet surface from about 0.5 MPa to about 3 MPa.

16. The adhesive polymer of claim 1, wherein the adhesive polymer has a viscosity of about 0.05 Pa.s to about 10 Pa.s.

17. The adhesive polymer of claim 1, wherein the adhesive polymer has a wet peel strength of about 0.4 N / mm to about 1 N / mm at a peel angle of 90 °.

18. A method of using the adhesive polymer of claim 1, which method comprises applying the adhesive polymer to at least a first substrate, which is to be adhered to at least a second substrate, and adhering the at least first substrate and the at least second substrate to each other such that the adhesive polymer is sandwiched therebetween.

19. The method of claim 18, which further comprises applying the adhesive composition to the at least second substrate prior to adhering the at least first substrate and the at least second substrate.

20. The method of claim 18 or 19, wherein the at least first substrate and / or the at least second substrate are exposed to moist, wet, or underwater conditions.

21. The method of claim 18 or 19, wherein the at least first substrate and / or the at least second substrate is metal, wood, plastic, rubber, polyurethane, Teflon®, polypropylene or a combination of two or more of the foregoing.

22. The method of claim 21, wherein the metal is steel or aluminum.

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