Coatings containing photonic particles for UV absorption

Abstract

Disclosed in certain embodiments is a coating composition and coating formed therefrom comprising a solvent, a binder, a UVA absorbing compound, and photonic particles such as porous metal oxide particles, hybrid metal oxide particles, closed-cell metal oxide particles, or a combination thereof. The coating compositions form a coating that exhibits a UV attenuation boost.

Description

240878W001COATINGS CONTAINING PHOTONIC PARTICLES FOR UV ABSORPTIONCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority from U.S. Provisional Patent Application No. 63 / 712,884, filed October 28, 2024, the disclosure of which is incorporated herein by reference.TECHNICAL FIELD

[0002] Disclosed are coatings compositions that incorporate materials for absorbance or attenuation of ultraviolet radiation.BACKGROUND

[0003] Traditional UV absorbers, such as benzotriazoles, have been widely used in coatings to provide protection from ultraviolet (UV) radiation. These absorbers work by absorbing UV light and converting it into less harmful forms of energy, typically heat, preventing UV-induced degradation such as fading, cracking, or yellowing. Benzotriazoles, in particular, are effective because they absorb a broad range of UV light and provide long-lasting protection for coatings on various surfaces, including automotive coatings. However, such materials raise environmental and toxicological concerns, which may impact their future use in coating systems.

[0004] These concerns have driven the exploration of alternative UV protection technologies that are more environmentally friendly and safe. There is thus a desire to develop more sustainable materials for UV absorption in view of increasing regulatory pressure and consumer demand for greener products.SUMMARY OF THE DISCLOSURE

[0005] The following presents a simplified summary of various aspects of the present disclosure in order to provide a basic understanding of such aspects. This summary is not an extensive overview of the disclosure. It is intended to neither identify key or critical elements of the disclosure, nor delineate any scope of the particular embodiments of the disclosure or any scope of the claims. Its sole purpose is to present some concepts of the disclosure in a simplified form as a prelude to the more detailed description that is presented later.

[0006] In at first aspect, a coating composition comprises: a solvent; a binder; a UVA absorbing compound; and photonic particles selected from porous metal oxide particles, hybrid metal oxide particles, closed-cell metal oxide particles, or a combination thereof, wherein a240878W001 coating formed from the coating composition exhibits a UV attenuation boost of at least about 50%.

[0007] In at least one embodiment, the UV attenuation boost is at least about 60%, at least about 70%, at least about 80%, at least about 90%, at least about 100%, at least about 110%, at least about 120%, at least about 130%, at least about 140%, at least about 150%, at least about 160%, at least about 170%, at least about 180%, at least about 190%, or at least about 200%.

[0008] In at least one embodiment, the photonic particles are present in the coating from about 0.5 wt% to about 2 wt% based on total dry weight of the coating.

[0009] In at least one embodiment, the UVA absorbing compound is present in the coating at less than about 3 wt%, less than about 2 wt%, less than about 1 wt%, or less than about 0.5 wt% based on total dry weight of the coating.

[0010] In at least one embodiment, the UVA absorbing compound comprises a hindered amine light stabilizer compound.

[0011] In at least one embodiment, the composition further comprises a component selected from: a dispersant; a surfactant; a defoaming agent; a co-dispersant; an acrylic binder; a rheology modifier; a coalescing agent; or a combination thereof.

[0012] In at least one embodiment, the composition further comprises the porous metal oxide particles, wherein the porous metal oxide particles have: an average diameter of from about 0.5 pm to about 100 pm; an average porosity of from about 0.45 to about 0.8; and at least one population of pores each having an average pore diameter of from about 100 nm to about 800 nm.

[0013] In at least one embodiment, the porous metal oxide particles have: an average diameter of from about 1 pm to about 75 pm; an average porosity of from about 0.45 to about 0.8; and at least one population of pores each having an average pore diameter of from about 100 nm to about 800 nm.

[0014] In at least one embodiment, the metal oxide of the porous metal oxide particles is selected from the group consisting of silica, titania, alumina, zirconia, ceria, iron oxide, zinc oxide, indium oxide, tin oxide, chromium oxide, and combinations thereof.

[0015] In at least one embodiment, the pores of the porous metal oxide particles form an ordered array or a disordered array.

[0016] In at least one embodiment, the composition comprises the hybrid metal oxide particles, wherein the hybrid metal oxide particles comprise a continuous matrix of a first metal oxide having embedded therein an array of metal oxide particles, the metal oxide particles240878W001 comprising a second metal oxide, wherein the hybrid metal oxide particles are substantially non- porous.

[0017] In at least one embodiment, the hybrid metal oxide particles have: an average diameter of from about 0.5 pm to about 50 pm; and an average diameter of the metal oxide particles of from about 100 nm to about 600 nm.

[0018] In at least one embodiment, the first metal oxide and the second metal oxide independently comprise a metal oxide selected from silica, titania, alumina, zirconia, ceria, iron oxides, zinc oxide, indium oxide, tin oxide, chromium oxide, and combinations thereof.

[0019] In at least one embodiment, the array of the metal oxide particles is an ordered array or a disordered array.

[0020] In at least one embodiment, the composition comprises the closed-cell metal oxide particles, wherein each closed-cell metal oxide particle comprises a metal oxide matrix defining an array of closed-cells, wherein each closed-cell encapsulates a media-inaccessible void volume, wherein the outer surface of the closed-cell metal oxide particle is defined by the array of closed-cells.

[0021] In at least one embodiment, the closed-cell metal oxide particles have: an average diameter of from about 1 pm to about 75 pm; an average void volume diameter of from about 50 nm to about 800 nm; and an average porosity of from about 0.45 to about 0.65.

[0022] In at least one embodiment, the closed-cell metal oxide particles have: an average diameter of from about 0.5 pm to about 50 pm; an average void volume diameter of from about 100 nm to about 800 nm; and an average porosity of from about 0.45 to about 0.65.

[0023] In at least one embodiment, the metal oxide matrix comprises a metal oxide selected from silica, titania, alumina, zirconia, ceria, iron oxides, zinc oxide, indium oxide, tin oxide, chromium oxide, and combinations thereof.

[0024] In at least one embodiment, the array of the closed-cells is an ordered array or a disordered array.

[0025] In a further aspect, a coating is derived from the composition of any preceding embodiment.

[0026] In a further aspect, a coating comprises a photosensitive colorant layer; and a clear coat layer disposed above the colorant layer to provide UV protection thereto, the clear coat laying being formed from the coating composition of any one of the preceding embodiments.

[0027] In at least one embodiment, the coating further comprises one or more additional layers (i) between a ground layer and the colorant layer, (ii) between the colorant layer and the clear coat layer, (iii) over the clear coat layer, or a combination thereof.240878W001

[0028] In a further aspect, an article of manufacture comprises a substrate and any of the preceding coatings. In at least one embodiment, the substrate is an automotive part. In at least one embodiment, the automotive part is an external panel or an interior part.

[0029] In a further aspect, a method of preparing a coating composition comprises mixing a solvent, a binder, and a photonic particles to obtain the coating composition of any of the preceding embodiments.

[0030] In a further aspect, a method of coating a substrate comprises layering the coating composition of any of the preceding embodiments onto a substrate.BRIEF DESCRIPTION OF DRAWINGS

[0031] The disclosure described herein is illustrated by way of example and not by way of limitation in the accompanying figures.

[0032] FIG. l is a schematic illustrating the morphology of porous metal oxide particles according to certain embodiments of the present disclosure.

[0033] FIG. 2A is a schematic illustrating a metal oxide particle with a closed-cell morphology according to certain embodiments of the present disclosure.

[0034] FIG. 2B illustrates a process of preparing metal oxide particles having closed-cell morphologies according to certain embodiments of the present disclosure.

[0035] FIG. 3 is a schematic illustrating a metal oxide particle with a hybrid metal oxide morphology according to certain embodiments of the present disclosure.

[0036] FIG. 4 shows an exemplary coating system comprising a photosensitive color layer having a clear coat layer for UV absorption deposited thereon according to certain embodiments of the present disclosure.

[0037] FIG. 5 is a UV-attenuation plot comparing the various clear coat formations.

[0038] FIG. 6A and 6B show the absorbance profiles measured for each of the clear coat samples.

[0039] FIG. 7 shows a visual comparison of coated samples.

[0040] FIGS. 8 and 9 show UV-attenuation curves for photonic particles in combination with various UV light absorbers.DETAILED DESCRIPTION

[0041] Embodiments of the present disclosure relate to the use of photonic particles in coatings and coating compositions for absorbance / attenuation of ultraviolet (UV) light. Such particles can be used alone or in combination with traditional UVA light absorbers to provide240878W001 enhanced UV attenuation. The effectiveness of such particles is demonstrated with coatings prepared with different formulations and measuring UV transmission, as discussed later in this disclosure.

[0042] The present embodiments demonstrates that photonic particles can attenuate UV light by themselves or exhibit synergistic effects in combination with traditional UVA light absorbers. Advantageously, the present embodiments can improve the UVA light absorber effectiveness in coating systems, including architectural, industrial, and automotive coatings applications. This enhancement allows for either increased efficiency at the same loading level or a reduction in the amount of UVA light absorber required in the system. Thus, advantages of the present disclosure include elimination, reduction and / or enhancement of traditional UVA light stabilizer materials in coating systems.

[0043] The mechanism through which the photonic particles describe herein provide UV protection depends on their structure and composition, as well as the coating system they are used in. Possible designs to achieve UV protection using photonic particles includes, but is not limited to:(1) Back-scattering: By designing the photonic particles to back-scatter the UV light, the particles near the surface can reflect UV before it reaches and damages the coating. This mechanism can work regardless of the presence of a UVA light stabilizer.(2) Total light scattering: Photonic particles can be designed to maximize total light scattering to increase the path length of light within the coating. This design is advantageous for clear coats that aim to protect a photosensitive pigment in a lower color layer. A UV absorber may also be utilized to absorb the scattered light.(3) Total internal reflection: Photonic particles can be designed to maximize total internal reflection, which would retain the photons inside the photonic particle structure until they are absorbed. A UV absorber may also be utilized in such embodiments.

[0044] In an exemplary embodiment, a coating composition comprises a solvent, a binder (e.g., an acrylic binder), a UVA absorbing compound (e.g, a benzotriazole), and any of the photonic particles described herein (e.g., porous metal oxide particles, hybrid metal oxide particles, closed-cell metal oxide particles, or a combination thereof). The concentrations of the UVA absorbing compound and the photonic particles may be selected for a target percent of the total dry weight of the coating once formed, which may result in the coating exhibiting a UV attenuation boost of at least about 50%.

[0045] As used herein the term “UV attenuation boost” is defined (Garget - C actual) / Cactual, where Garget is the concentration of the UVA absorbing compound needed to achieve a target240878W001 transmittance in a coating based on an attenuation curve for the UVA absorbing compound, and Cactuai is the actual concentration of the UVA absorbing compound in the coating. UV attenuation boost can provide a measure of increased UV attenuation performance by utilizing photonic particles in combination with lower concentrations of the UVA absorbing compound, effectively offsetting the UVA absorbing compound to achieve a similar result.

[0046] Certain embodiments are directed to coatings derived from the coating compositions disclosed herein.

[0047] Certain embodiments further comprise a clear coat layer, wherein the clear coat is layered over a pigmented coating. In at least one embodiment, photonic particles and UVA absorbing compounds are present in the clear coat.

[0048] Certain embodiments further comprise one or more additional layers (i) between a ground layer and a colorant layer, (ii) between the colorant layer and a clear coat layer, (iii) over the clear coat layer, (iv) under the ground layer, or a combination thereof. The photonic particles can be included in one or more of the ground layer, the colorant layer, the clear coat layer or any of the additional layers.

[0049] In at least one embodiment, photonic particles having similar morphologies to those described herein may also be used as structural colorants. For example, photonic particles having optical effects in the visible light spectrum (e.g., exhibiting angle-dependent or angleindependent color) may be present in a colorant layer, and photonic particles having UV absorption characteristics may be present in the colorant layer or in a clear coat layer disposed on the colorant layer.

[0050] The term “micro” or “micro-scaled” means from about 0.5 pm to about 999 pm. The term “nano” or “nano-scaled” means from about 1 nm to about 999 nm.

[0051] The term “monodisperse” in reference to a population of particles means particles having generally uniform shapes and generally uniform diameters. A present monodisperse population of particles for instance may have 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% of the particles by number having diameters within ± 7%, ± 6%, ± 5%, ± 4%, ± 3%, ± 2% or ± 1% of the average diameter of the population.

[0052] Removal of a monodisperse population of polymer particles provides porous metal oxide particles having a corresponding population of pores having an average pore diameter.

[0053] The term “substantially free of other components” means for example containing < 5 %, < 4 % ,< 3 %, < 2 %, < 1 % or < 0.5 % by weight of other components.

[0054] The articles “a” and “an” herein refer to one or to more than one (e.g. at least one) of the grammatical object. Any ranges cited herein are inclusive. The term “about” used240878W001 throughout is used to describe and account for small fluctuations. For instance, “about” may mean the numeric value may be modified by ± 5%, ± 4%, ± 3%, ±2%, ±1%, ±0.5%, ±0.4%, ±0.3%, ±0.2%, ±0.1% or ±0.05%. All numeric values are modified by the term “about” whether or not explicitly indicated. Numeric values modified by the term “about” include the specific identified value. For example “about 5.0” includes 5.0.

[0055] The terms “particles”, “microspheres”, “nanospheres”, “droplets”, etc., referred to herein may mean for example a plurality thereof, a collection thereof, a population thereof, a sample thereof or a bulk sample thereof.

[0056] The term “of’ may mean “comprising”, for instance “a liquid dispersion of’ may be interpreted as “a liquid dispersion comprising”.

[0057] U.S. patents, U.S. patent applications and published U.S. patent applicants discussed herein are hereby incorporated by reference.

[0058] Unless otherwise indicated, all parts and percentages are by weight. Weight percent (wt%), if not otherwise indicated, is based on an entire composition free of any volatiles, that is, based on dry solids content.1. Photonic Particles

[0059] Certain embodiments further relate to coating compositions that incorporate photonic particles, such as automotive coatings. As used herein, the term “photonic particles” refers to particles that exhibit light absorption characteristics due to their structural morphology / architecture rather than molecular properties. In particular, the particles can exhibit UV absorption, infrared absorption, and / or color via light interference effects, relying on microscopically structured surfaces small enough to interfere with light and exhibit optical effects as opposed to their chemical structure. The properties that result from this mechanism can be selected by alterations to the structure of a chosen material, allowing one material to exhibit various optical effects with no change to the chemical nature of the material itself. The creation of these particles through colloidal dispersion procedures and their optimization for UV absorption is discussed herein.

[0060] The term “porous,” as used herein, refers to one or more interconnected or noninterconnected pores, voids, spaces, or interstices that allow air or liquid to pass through. The term “porosity” as used herein refers to a measure of the empty spaces (or voids or pores) in the particles and is a ratio of the volume of voids to total volume of the mass of the photonic particles between 0 and 1, or as a percentage between 0 and 100%. Average porosity of the photonic particles means the total pore volume, as a fraction of the volume of the entire photonic240878W001 particle. Mercury porosimetry analysis can be used to characterize the porosity of the particles. Mercury porosimetry applies controlled pressure to a sample immersed in mercury. External pressure is applied for the mercury to penetrate into the voids / pores of the material. The amount of pressure required to intrude into the voids / pores is inversely proportional to the size of the voids / pores. A mercury porosimeter generates volume and pore size distributions from the pressure versus intrusion data generated by the instrument using the Washbum equation. Porosity, as reported herein for photonic particles, is calculated as a ratio of unoccupied space and total particle volume. For example, porous silica particles containing voids / pores with an average size of 165 nm have an average porosity of 0.8.

[0061] The average particle diameter (also referred to herein as average particle size) of the particles can be determined by scanning electron microscopy (SEM) or transmission electron microscopy (TEM). Particle size may also be measured by laser light scattering techniques with dispersions or dry powders. Average particle size is synonymous with D50, meaning half of the population resides above this point, and half below.

[0062] The term “metal oxide” refers to oxygen containing species of various metals, such as silicon, titanium, aluminum, zirconium, cerium, iron, zinc, indium, tin, chromium, antimony, bismuth, cobalt, gallium, lanthanum, molybdenum, neodymium, nickel, niobium, vanadium, or combinations thereof.

[0063] In at least one embodiment, photonic particles are produced utilizing one or more microfluidic devices. Microfluidic devices are, for example, narrow channel devices having a micron-scaled droplet junction adapted to produce uniform size droplets, with the channels being connected to a collection reservoir. Microfluidic devices, for example, contain a droplet junction having a channel width of from about 10 pm to about 100 pm. The devices are, for example, made of polydimethylsiloxane (PDMS) and may be fabricated, for example, via soft lithography. An emulsion may be prepared within the device via pumping an aqueous dispersed phase and oil continuous phase at specified rates to the device where mixing occurs to provide emulsion droplets. Alternatively, an oil-in-water emulsion may be utilized. The continuous oil phase comprises, for example, an organic solvent, a silicone oil, or a fluorinated oil. As used herein, “oil” refers to an organic phase (e.g., an organic solvent) immiscible with water. Organic solvents include hydrocarbons, for example, heptane, hexane, toluene, xylene, and the like.

[0064] In at least one embodiment, the photonic particles described herein may exhibit angle-dependent properties (e.g., color properties, or other light absorbing characteristics) or angle-independent properties. “Angle-dependent” properties means that exhibited properties have dependence on the angle of incident light on a sample or on the angle between the observer240878W001 and the sample. “Angle-independent” properties means that exhibited properties have substantially no dependence on the angle of incident light on a sample or on the angle between the observer and the sample.

[0065] The term “bulk sample” means a population of particles. For example, a bulk sample of particles is simply a bulk population of particles, for instance > 0.1 mg, > 0.2 mg, > 0.3 mg, > 0.4 mg, > 0.5 mg, > 0.7 mg, > 1.0 mg, > 2.5 mg, > 5.0 mg, > 10.0 mg or > 25.0 mg. A bulk sample of particles may be substantially free of other components.

[0066] The phrase “exhibits color observable by the human eye” means color will be observed by an average person. This may be for any bulk sample distributed over any surface area, for instance a bulk sample distributed over a surface area of from any of about 1 cm2, about 2 cm2, about 3 cm2, about 4 cm2, about 5 cm2or about 6 cm2to any of about 7 cm2, about 8 cm2, about 9 cm2, about 10 cm2, about 11 cm2, about 12 cm2, about 13 cm2, about 14 cm2or about 15 cm2. It may also mean observable by a CIE 1931 2° standard observer and / or by a CIE 1964 10° standard observer. The background for color observation may be any background, for instance a white background, black background or a dark background anywhere between white and black.

[0067] The following sections discuss photonic particles with various architectures, including porous metal oxide particles, closed-cell metal oxide particles, and hybrid metal oxide particles. It is to be understood that each of these architectures is exemplary, and any one of the photonic particles described, or various combinations thereof, could be utilized by themselves or in combination with other UV absorbing materials in coatings or coating compositions as described herein.1.1 Porous Metal Oxide Particles

[0068] FIG. l is a schematic illustrating the open architecture of porous metal oxide particles. Porous metal oxide particles with a single pore population and porous metal oxide particles with multiple pore populations may be produced, for example, as described, respectively, in International Application No. PCT / US2018 / 050168, filed September 11, 2017, and International Application No. PCT / US2018 / 050175, filed September 11, 2017, the disclosures of which are hereby incorporated by reference herein in their entireties. An emulsion droplet containing polymer template particles (or “polymer particles”) and metal oxide is dried to remove solvent, providing an assembled microsphere containing polymer particles with metal oxide particles in the interstitial spaces between the polymer particles (template microsphere or “direct structure”). The polymer particles define the interstitial space. Calcination results in240878W001 removal of the polymer, providing a present metal oxide microsphere with high porosity, or void volume (inverse structure).

[0069] The resulting porous metal oxide particles may be spherical and micrometer-scaled, for example, having average diameters from about 0.5 pm to about 100 pm. In certain embodiments, the porous metal oxide particles have an average diameter from about 0.5 pm, about 0.6 pm, about 0.7 pm, about 0.8 pm, about 0.9 pm, about 1.0 pm, about 5.0 pm, about 10 pm, about 20 pm, about 30 pm, about 40 pm, about 50 pm, about 60 pm, about 70 pm, about 80 pm, about 90 pm, about 100 pm, or within any range defined by any of these average diameters (e.g., about 1.0 pm to about 20 pm, about 5.0 pm to about 50 pm, etc.). The metal oxide employed may also be in particle form, and may be nano-scaled. The metal oxide matrix particles may have an average diameter, for example, of about 1 nm to about 120 nm. The polymer template particles may have an average diameter, for example, of about 50 nm to about 500 nm. One or more of the polymer particles or the metal oxide particles may be polydisperse or monodisperse. In certain embodiments, polymer particles corresponding to different size distributions may be utilized to produce porous metal oxide particles having multiple populations of pore sizes characterized by different average pore diameters. In certain embodiments, the metal oxide may be provided as metal oxide particles or may be formed from a metal oxide precursor, for example, via a sol-gel technique.

[0070] Certain embodiments of the porous metal oxide particles exhibit color in the visible spectrum at a wavelength range selected from the group consisting of 380 nm to 450 nm, 451 nm to 495 nm, 496 nm to 570 nm, 571 nm to 590 nm, 591 nm to 620 nm, 621 nm to 750 nm, 751 nm to 800 nm, and any range defined therebetween (e.g., 496 nm to 620 nm, 450 nm to 750 nm, etc.). In certain embodiments, the particles exhibit a wavelength range in the ultraviolet spectrum selected from the group consisting of 100 nm to 400 nm, 100 nm to 200 nm, 200 nm to 300 nm, and 300 nm to 400 nm.

[0071] In certain embodiments, the porous metal oxide particles can have, for example, one or more of an average diameter of from about 0.5 pm to about 100 pm, an average porosity of greater than about 0.1, greater than about 0.2, greater than about 0.3, greater than about 0.4, greater than about 0.5, greater than about 0.6, greater than about 0.7, greater than about 0.8, or about 0.10 to about 0.80, and an average pore diameter of from about 50 nm to about 500 nm. In other embodiments, the particles can have, for example, one or more of an average diameter of from about 1 pm to about 75 pm, an average porosity of from about 0.10 to about 0.40, and an average pore diameter of from about 50 nm to about 800 nm.240878W001

[0072] In certain embodiments, the porous metal oxide particles have an average diameter, for example, of from about 1 pm to about 75 pm, from about 2 pm to about 70 pm, from about 3 pm to about 65 pm, from about 4 pm to about 60 pm, from about 5 pm to about 55 pm, or from about 5 pm to about 50 pm; for example, from any of about 5 pm, about 6 pm, about 7 pm, about 8 pm, about 9 pm, about 10 pm, about 11 pm, about 12 pm, about 13 pm, about 14 pm, or about 15 pm to any of about 16 pm, about 17 pm, about 18 pm, about 19 pm, about 20 pm, about 21 pm, about 22 pm, about 23 pm, about 24 pm, or about 25 pm. Other embodiments can have an average diameter of from any of about 4.5 pm, about 4.8 pm, about 5.1 pm, about 5.4 pm, about 5.7 pm, about 6.0 pm, about 6.3 pm, about 6.6 pm, about 6.9 pm, about 7.2 pm, or about 7.5 pm to any of about 7.8 pm about 8.1 pm, about 8.4 pm, about 8.7 pm, about 9.0 pm, about 9.3 pm, about 9.6 pm, or about 9.9 pm.

[0073] In certain embodiments, the porous metal oxide particles have an average porosity, for example, of from any of about 0.10, about 0.12, about 0.14, about 0.16, about 0.18, about 0.20, about 0.22, about 0.24, about 0.26, about 0.28, about 0.30, about 0.32, about 0.34, about0.36, about 0.38, about 0.40, about 0.42, about 0.44, about 0.46, about 0.48 about 0.50, about0.52, about 0.54, about 0.56, about 0.58, or about 0.60 to any of about 0.62, about 0.64, about0.66, about 0.68, about 0.70, about 0.72, about 0.74, about 0.76, about 0.78, about 0.80, or about0.90. Other embodiments can have an average porosity of from any of about 0.45, about 0.47, about 0.49, about 0.51, about 0.53, about 0.55, or about 0.57 to any of about 0.59, about 0.61, about 0.63, or about 0.65. For example, the porous metal oxide particles can have an average porosity of from 0.10 to 0.90, from 0.10 to 0.80, from 0.15 to 0.80, from 0.20 to 0.70, from 0.20 to 0.60, from 0.45 to 0.70, from 0.40 to 0.65, from 0.45 to 0.65, or from 0.45 to 0.55.

[0074] The porous metal oxide particles can contain uniform or non-uniform pore diameters.

[0075] In some embodiments, the metal oxide particles have an average pore diameter, for example, of from any of about 100 nm, about 120 nm, about 140 nm, about 160 nm, about 180 nm, about 200 nm, about 220 nm, about 240 nm, about 260 nm, about 280 nm, about 300 nm, about 320 nm, about 340 nm, about 360 nm, about 380 nm, about 400 nm, about 420 nm, or about 440 nm to any of about 460 nm, about 480 nm, about 500 nm, about 520 nm, about 540 nm, about 560 nm, about 580 nm, about 600 nm, about 620 nm, about 640 nm, about 660 nm, about 680 nm, about 700 nm, about 720 nm, about 740 nm, about 760 nm, about 780 nm, or about 800 nm. Other embodiments can have an average pore diameter of from any of about 220 nm, about 225 nm, about 230 nm, about 235 nm, about 240 nm, about 245 nm, or about 250 nm to any of about 255 nm, about 260 nm, about 265 nm, about 270 nm, about 275 nm, about 280240878W001 nm, about 285 nm, about 290 nm, about 295 nm, or about 300 nm. Average pore diameter can be determined by electron microscopy.

[0076] In certain embodiments, the polymer of the polymer particles is selected from poly(meth)acrylic acid, poly(meth)acrylates, polystyrenes, polyacrylamides, polyvinyl alcohol, polyvinyl acetate, polyesters, polyurethanes, polyethylene, polypropylene, polylactic acid, polyacrylonitrile, polyvinyl ethers, derivatives thereof, salts thereof, copolymers thereof, or combinations thereof. For example, the polymer is selected from the group consisting of polymethyl methacrylate, polyethyl methacrylate, poly(n-butyl methacrylate), polystyrene, poly(chloro-styrene), poly (alpha-methyl styrene), poly(N-methylolacrylamide), styrene / methyl methacrylate copolymer, polyalkylated acrylate, polyhydroxyl acrylate, polyamino acrylate, polycyanoacrylate, polyfluorinated acrylate, poly(N-methylolacrylamide), polyacrylic acid, polymethacrylic acid, methyl methacrylate / ethyl acrylate / acrylic acid copolymer, styrene / methyl methacrylate / acrylic acid copolymer, polyvinyl acetate, polyvinylpyrrolidone, polyvinylcaprolactone, polyvinylcaprolactam, a co-polymer of methyl methacrylate and [2- (methacryloyloxy)ethyl]trimethylammonium chloride, derivatives thereof, salts thereof, or combinations thereof.

[0077] In certain embodiments, the metal oxide material of the porous metal oxide particles is selected from silica, titania, alumina, zirconia, ceria, iron oxides, zinc oxide, indium oxide, tin oxide, chromium oxide, or combinations thereof. In certain embodiments, the metal oxide comprises SiCh, TiCh, Ti20s, AI2O3, or Fe2C>3.

[0078] In certain embodiments, a weight to weight ratio of the metal oxide particles to the polymer particles is from about 1 / 10, about 2 / 10, about 3 / 10, about 4 / 10, about 5 / 10 about 6 / 10, about 7 / 10, about 8 / 10, about 9 / 10, to about 10 / 9, about 10 / 8, about 10 / 7, about 10 / 6, about 10 / 5, about 10 / 4, about 10 / 3, about 10 / 2, or about 10 / 1. In certain embodiments, the weight to weight ratio of the metal oxide particles to the polymer particles is 1 / 3, 2 / 3, 1 / 1, or 3 / 2.

[0079] In further embodiments, the porous metal oxide particles can have, e.g., from about 60.0 wt% to about 99.9 wt% metal oxide, based on the total weight of the porous metal oxide particles. In other embodiments, the porous metal oxide particles comprise from about 0.1 wt% to about 40.0 wt% of one or more light absorbers, based on the total weight of the porous metal oxide particles. In other embodiments, the metal oxide is from any of about 60.0 wt%, about 64.0 wt%, about 67.0 wt%, about 70.0 wt%, about 73.0 wt%, about 76.0 wt%, about 79.0 wt%, about 82.0 wt% or about 85.0 wt% to any of about 88.0 wt%, about 91.0 wt%, about 94.0 wt%, about 97.0 wt%, about 98.0 wt%, about 99.0 wt% or about 99.9 wt% metal oxide, based on the total weight of the porous metal oxide particles.240878W001

[0080] In certain embodiments, the porous metal oxide particles are prepared by a process comprising forming a liquid dispersion of polymer particles and metal oxide particles; forming liquid droplets of the dispersion; drying the liquid droplets to provide polymer template particles comprising polymer and metal oxide; and removing the polymer to provide porous metal oxide particles. In such embodiments, the resulting pores are monodisperse.

[0081] In certain embodiments, the porous metal oxide particles are prepared by a method comprising: generating liquid droplets from a particle dispersion comprising metal oxide particles and polymer particles; drying the liquid droplets to provide dried particles; and calcining or sintering the dried particles to densify the metal oxide particle matrix and remove the polymer particles, resulting in porous metal oxide particles.

[0082] In certain embodiments, the evaporation of the liquid medium may be performed in the presence of self-assembly substrates such as conical tubes or silicon wafers. In certain embodiments, dried particle mixtures may be recovered, e.g., by filtration or centrifugation. In certain embodiments, the drying comprises microwave irradiation, oven drying, drying under vacuum, drying in the presence of a desiccant, or a combination thereof.

[0083] In certain embodiments utilizing liquid droplets, the droplets are formed with a microfluidic device. The microfluidic device can contain a droplet junction having a channel width, for example, of from any of about 10 pm, about 15 pm, about 20 pm, about 25 pm, about 30 pm, about 35 pm, about 40 pm, or about 45 pm to any of about 50 pm, about 55 pm, about 60 pm, about 65 pm, about 70 pm, about 75 pm, about 80 pm, about 85 pm, about 90 pm, about 95 pm, or about 100 pm.

[0084] In certain embodiments, generating and drying the liquid droplets is performed using a spray-drying process. In certain embodiments of spray-drying techniques, a feed of a liquid solution or dispersion is fed (e.g. pumped) to an atomizing nozzle associated with a compressed gas inlet through which a gas is injected. The feed is pumped through the atomizing nozzle to form liquid droplets. The liquid droplets are surrounded by a pre-heated gas in an evaporation chamber, resulting in evaporation of solvent to produce dried particles. The dried particles are carried by the drying gas through a cyclone 314 and deposited in a collection chamber. Gases include nitrogen and / or air. In an embodiment of an exemplary spray-drying process, a liquid feed contains a water or oil phase, the metal oxide, and the polymer particles.

[0085] Air may be considered a continuous phase with a dispersed liquid phase (a liquid-ingas emulsion). In certain embodiments, spray-drying comprises an inlet temperature of from any of about 100°C, about 105°C, about 110°C, about 115°C, about 120°C, about 130°C, about 140°C, about 150°C, about 160°C, or about 170°C to any of about 180°C, about 190°C, about240878W001200°C, about 210°C, about 215°C, or about 220°C. In certain embodiments a pump rate (feed flow rate) of from any of about 1 mL / min, about 2 mL / min, about 5 mL / min, about 6 mL / min, about 8 mL / min, about 10 mL / min, about 12 mL / min, about 14 mL / min, or about 16 mL / min to any of about 18 mL / min, about 20 mL / min, about 22 mL / min, about 24 mL / min, about 26 mL / min, about 28 mL / min, or about 30 mL / min is utilized.

[0086] In certain embodiments, vibrating nozzle techniques may be employed. In such techniques, a liquid dispersion is prepared, and then droplets are formed and dropped into a bath of a continuous phase. The droplets are then dried. Vibrating nozzle equipment is available from BUCHI and comprises, for example, a syringe pump and a pulsation unit. Vibrating nozzle equipment may also comprise a pressure regulation valve.

[0087] In certain embodiments, polymer removal may be performed, for example, via calcination, pyrolysis, or with a solvent (solvent removal). Calcination is performed in certain embodiments at temperatures of at least about 200°C, at least about 500°C, at least about 1000°C, from about 200°C to about 1200°C, or from about 200°C to about 700°C. The calcining can be for a suitable period, e.g., from about 0.1 hour to about 12 hours or from about 1 hour to about 8.0 hours. In other embodiments, the calcining can be for at least about 0.1 hour, at least about 1 hour, at least about 5 hours, or at least about 10 hours. In other embodiments, the calcining can be from any of about 200°C, about 350°C, about 400°C, 450°C, about 500°C or about 550°C to any of about 600°C, about 650°C, about 700°C, or about 1200°C for a period of from any of about 0.1 h (hour), about 1 h, about 1.5 h, about 2.0 h, about 2.5 h, about 3.0 h, about 3.5 h, or about 4.0 h to any of about 4.5 h, about 5.0 h, about 5.5 h, about 6.0 h, about 6.5 h, about 7.0 h, about 7.5 h about 8.0 h, or about 12 h.

[0088] In certain embodiments, a particle size ratio of the metal oxide particles to the polymer particles is from 1 / 50 to 1 / 5 (e.g., 1 / 10).

[0089] In certain embodiments, the metal oxide particles have an average diameter of from about 1 nm, about 5 nm, about 10 nm, about 15 nm, about 20 nm, about 25 nm, about 30 nm, about 35 nm, about 40 nm, about 45 nm, about 50 nm, about 55 nm, or about 60 nm to about 65 nm, about 70 nm, about 75 nm, about 80 nm, about 85 nm, about 90 nm, about 95 nm, about 100 nm, about 105 nm, about 110 nm, about 115 nm, or about 120 nm. In other embodiments, the matrix nanoparticles have an average diameter of about 5 nm to about 150 nm, about 50 to about 150 nm, or about 100 to about 150 nm.

[0090] In certain embodiments, the polymer particles have an average diameter of from about 50 nm to about 990 nm. In other embodiments, the particles have an average diameter of from any of about 50 nm, about 75 nm, about 100 nm, about 130 nm, about 160 nm, about240878W001190 nm, about 210 nm, about 240 nm, about 270 nm, about 300 nm, about 330 nm, about 360 nm, about 390 nm, about 410 nm, about 440 nm, about 470 nm, about 500 nm, about 530 nm, about 560 nm, about 590 nm, or about 620 nm to any of about 650 nm, about 680 nm, about 710 nm, about 740 nm, about 770 nm, about 800 nm, about 830 nm, about 860 nm, about 890 nm, about 910 nm, about 940 nm, about 970 nm, or about 990 nm.

[0091] In certain embodiments, removing the polymer particles comprises calcination, pyrolysis, or solvent removal. The calcining of the polymer particles can be, e.g., at temperatures of from about 300°C to about 800°C for a period of from about 1 hour to about 8 hours.

[0092] In certain embodiments, the porous metal oxide particles comprise mainly metal oxide, that is, they may consist essentially of or consist of metal oxide. Advantageously, depending on the particle compositions, relative sizes, and shapes of the metal oxide particles used, a bulk sample of the porous metal oxide particles may exhibit color observable by the human eye, may appear white, or may exhibit properties in the UV spectrum. A light absorber may also be present within (e.g., encapsulated by or embedded within) the particles or physically mixed with the particles, such as a UV-absorbing compound. Absorbers include inorganic and organic materials, for example, a broadband absorber such as carbon black. Absorbers may, for example, be added by physically mixing the particles and the absorbers together or by including the absorbers in the droplets to be dried.

[0093] Angle-dependent optical properties may be achieved, for example, with the use of monodisperse polymer particles. Angle-dependent optical properties may also be achieved when a step of drying the liquid droplets is performed slowly, allowing the particles to become ordered. Angle-independent optical properties may be achieved when a step of drying the liquid droplets is performed quickly, not allowing the particles to become ordered.

[0094] In certain embodiments, the metal oxide particles can comprise combinations of different types of particles. For example, the metal oxide particles may be a mixture of two different metal oxides (i.e., discrete distributions of metal oxide particles), such as a mixture of alumina particles and silica particles with each species being characterized by the same or similar size distributions.

[0095] In certain embodiments, the metal oxide particles may comprise more complex compositions and / or morphologies. For example, the metal oxide particles may comprise particles such that each individual particle comprises two or more metal oxides (e.g., silica- titania particles). Such particles may comprise, for example, a mixture of two or more metal oxides.240878W001

[0096] In certain embodiments, the metal oxide particles and / or the polymer particles may comprise surface functionalization. An example of a surface functionalization is a silane coupling agent (e.g., silane-functionalized silica). In certain embodiments, the surface functionalization is performed on the metal oxide particles prior to self-assembly and densification.

[0097] To obtain reflectance over a wide spectral range, more than one type (a blend) of porous metal oxide particles can be incorporated in the coating compositions. A combination of two porous metal oxide particles can increase the spectral range over which reflectance is observed. In certain embodiments, the porous metal oxide particles exhibit an ability to disperse well into the coating compositions and thus uniformly coat a surface. In particular, the porous metal oxide particles are compatible with all types of solvent and coating systems such as acrylics and styrene-acrylic systems.1.2 Closed-Cell Metal Oxide Particles

[0098] Certain embodiments relate to coating compositions that incorporate closed-cell metal oxide particles as photonic particles, for example, for UV absorption. Closed-cell metal oxide particles comprise a metal oxide matrix having an array of pores (referred to as “void volumes” or “voids,” which may comprise air) formed therein of substantially uniform sizes, as illustrated by a cross-sectional view in FIG. 2A. As illustrated, the closed-cell metal oxide particle is formed from a metal oxide matrix which defines an array of “closed-cells” that encapsulate media-inaccessible void volumes. An outer surface of the closed-cell metal oxide particle (depicted as an overcoated surface formed by the metal oxide) is defined by the array of closed- cells such that there are substantially no open pores of similar size to the closed-cells at the surface.

[0099] Advantageously, the closed-cell metal oxide particles of the present embodiments are impermeable to polymers, large molecules, or other viscous materials frequently used in coating formulations, and thus can prevent penetration into the pores and retaining air in the pores.Thus, the close-cell metal oxide particles advantageously maintain a constant net refractive index between the matrix and voids regardless of the surrounding media in the application.

[0100] Closed-cell metal oxide particles have physical parameters that can be tuned to enhance performance properties of their corresponding coating compositions. By way of example, and not to be considered limiting, physical parameters that can be adjusted include the particle size diameters, particle size distributions, particle shapes, void volume (pore) diameter within the particles, porosity, packing density, surface texture, and the degree of order with240878W001 regard to the spatial arrangement of the closed-cells of the particles. Chemical parameters that can be adjusted include the chemical make-up of the particles, including the composition of the matrix and surface functionalizations. When used in coating compositions, the particles can be added in a sufficient amount to enhance reflective properties and optionally replace existing components such as pigments and / or fillers in the coating compositions. The terms “tuned,” “adjusted,” and “configured” can be used interchangeably and refer to an adjustment to a physical and / or chemical parameter of the particles to change their reflectance properties. The closed-cell metal oxide particles described herein can exhibit high stability and thus can be formulated into coating compositions as a replacement for less stable and / or less environmentally friendly components.

[0101] Depending upon the physical parameters of the closed-cell metal oxide particles, they can have a broad range of uses in coating compositions. The closed-cell metal oxide particles can be synthesized as to adjust (1) the microsphere size diameter, (2) the void volume diameters within the closed-cell metal oxide particles (3) the degree of order with regards to the spatial arrangement of the voids in the closed-cell metal oxide particles, and (4) the average distance between the void volumes.

[0102] Closed-cell metal oxide particles may be produced, for example, as described in International Application No. PCT / IB2021 / 000499, filed on July 21, 2021, the disclosure of which is hereby incorporated by reference herein in its entirety. FIG. 2B illustrates an exemplary process for forming the closed-cell metal oxide particles. In certain embodiments, the closedcell metal oxide particles are produced by drying droplets of a formulation comprising a matrix of metal oxide particles on the order of 1 to 120 nm in diameter, and polymer particles on the order of 50 to 500 nm which will serve as the template. In certain embodiments, the two particle species are oppositely charged (e.g., positively charged polymer particles and negatively charged metal oxide particles) to facilitate formation of a coating of the metal oxide particles on the polymer particles. In certain embodiments, a spray drying or microfluidics process is used to generate the droplets (e.g., aqueous droplets), and the droplets are dried to remove their solvent. In certain embodiments that utilize a spray drying process, the generation of droplets and drying is performed in rapid succession. During the drying process, the polymer particles and the metal oxide particles self-assemble to form a microsphere containing polymer particles embedded in a metal oxide matrix. By sintering the matrix nanoparticles, for example, in a muffle furnace, the matrix nanoparticles densify and form a stable matrix around the polymer particles. During this process, the polymer particles are removed via calcination, resulting in a final closed-cell particle having an array of closed-cells formed therein.240878W001

[0103] The resulting closed-cell metal oxide particles may be spherical and micrometer- scaled, for example, having average diameters from about 0.5 pm to about 50 pm. In certain embodiments, the closed-cell metal oxide particles have an average diameter from about 0.5 pm, about 0.6 pm, about 0.7 pm, about 0.8 pm, about 0.9 pm, about 1.0 pm, about 5.0 pm, about 10 pm, about 20 pm, about 30 pm, about 40 pm, about 50 pm, or within any range defined by any of these average diameters (e.g., about 1.0 pm to about 20 pm, about 5.0 pm to about 50 pm, etc.). The metal oxide employed may also be in particle form, and may be nano-scaled. The metal oxide matrix particles may have an average diameter, for example, of about 1 nm to about 120 nm. The polymer template particles may have an average diameter, for example, of about 50 nm to about 500 nm. One or more of the polymer particles or the metal oxide particles may be polydisperse or monodisperse. In certain embodiments, the metal oxide may be provided as metal oxide particles or may be formed from a metal oxide precursor, for example, via a sol-gel technique.

[0104] Certain embodiments of the closed-cell metal oxide particles exhibit color in the visible spectrum at a wavelength range selected from the group consisting of 380 nm to 450 nm, 451 nm to 495 nm, 496 nm to 570 nm, 571 nm to 590 nm, 591 nm to 620 nm, 621 nm to 750 nm, 751 nm to 800 nm, and any range defined therebetween (e.g., 496 nm to 620 nm, 450 nm to 750 nm, etc.). In certain embodiments, the particles exhibit a wavelength range in the ultraviolet spectrum selected from the group consisting of 100 nm to 400 nm, 100 nm to 200 nm, 200 nm to 300 nm, and 300 nm to 400 nm.

[0105] In certain embodiments, the closed-cell metal oxide particles can have, for example, one or more of an average diameter of from about 0.5 pm to about 100 pm, an average porosity of greater than about 0.1, greater than about 0.2, greater than about 0.3, greater than about 0.4, greater than about 0.5, greater than about 0.6, greater than about 0.7, greater than about 0.8, or about 0.10 to about 0.80, and an average void volume (pore) diameter of from about 50 nm to about 500 nm. In other embodiments, the particles can have, for example, one or more of an average diameter of from about 1 pm to about 75 pm, an average porosity of from about 0.10 to about 0.40, and an average void volume (pore) diameter of from about 50 nm to about 800 nm.

[0106] In certain embodiments, the closed-cell metal oxide particles have an average diameter, for example, of from about 1 pm to about 75 pm, from about 2 pm to about 70 pm, from about 3 pm to about 65 pm, from about 4 pm to about 60 pm, from about 5 pm to about 55 pm, or from about 5 pm to about 50 pm; for example, from any of about 5 pm, about 6 pm, about 7 pm, about 8 pm, about 9 pm, about 10 pm, about 11 pm, about 12 pm, about 13 pm, about 14 pm, or about 15 pm to any of about 16 pm, about 17 pm, about 18 pm, about 19 pm,240878W001 about 20 pm, about 21 pm, about 22 pm, about 23 pm, about 24 pm, or about 25 pm. Other embodiments can have an average diameter of from any of about 4.5 gm, about 4.8 gm, about 5.1 pm, about 5.4 gm, about 5.7 gm, about 6.0 gm, about 6.3 gm, about 6.6 gm, about 6.9 gm, about 7.2 pm, or about 7.5 gm to any of about 7.8 gm about 8.1 gm, about 8.4 gm, about 8.7 pm, about 9.0 gm, about 9.3 gm, about 9.6 gm, or about 9.9 gm.

[0107] In certain embodiments, the closed-cell metal oxide particles have an average porosity, for example, of from any of about 0.10, about 0.12, about 0.14, about 0.16, about 0.18, about 0.20, about 0.22, about 0.24, about 0.26, about 0.28, about 0.30, about 0.32, about 0.34, about 0.36, about 0.38, about 0.40, about 0.42, about 0.44, about 0.46, about 0.48 about 0.50, about 0.52, about 0.54, about 0.56, about 0.58, or about 0.60 to any of about 0.62, about 0.64, about 0.66, about 0.68, about 0.70, about 0.72, about 0.74, about 0.76, about 0.78, about 0.80, or about 0.90. Other embodiments can have an average porosity of from any of about 0.45, about 0.47, about 0.49, about 0.51, about 0.53, about 0.55, or about 0.57 to any of about 0.59, about 0.61, about 0.63, or about 0.65. For example, the closed-cell metal oxide particles can have an average porosity of from 0.10 to 0.90, from 0.10 to 0.80, from 0.15 to 0.80, from 0.20 to 0.70, from 0.20 to 0.60, from 0.45 to 0.70, from 0.40 to 0.65, from 0.45 to 0.65, or from 0.45 to 0.55.

[0108] The closed-cell metal oxide particles can contain uniform or non-uniform pore diameters.

[0109] In certain embodiments, the closed-cell metal oxide particles have an average void volume (pore) diameter of, for example, about 100 nm, about 120 nm, about 140 nm, about 160 nm, about 180 nm, about 200 nm, about 220 nm, about 240 nm, about 260 nm, about 280 nm, about 300 nm, about 320 nm, about 340 nm, about 360 nm, about 380 nm, about 400 nm, about 420 nm, or about 440 nm to any of about 460 nm, about 480 nm, about 500 nm, about 520 nm, about 540 nm, about 560 nm, about 580 nm, about 600 nm, about 620 nm, about 640 nm, about 660 nm, about 680 nm, about 700 nm, about 720 nm, about 740 nm, about 760 nm, about 780 nm, or about 800 nm. Other embodiments can have an average void volume (pore) diameter of from any of about 220 nm, about 225 nm, about 230 nm, about 235 nm, about 240 nm, about 245 nm, or about 250 nm to any of about 255 nm, about 260 nm, about 265 nm, about 270 nm, about 275 nm, about 280 nm, about 285 nm, about 290 nm, about 295 nm, or about 300 nm. Average pore diameter can be determined by electron microscopy.

[0110] In certain embodiments, the polymer of the polymer particles is selected from poly(meth)acrylic acid, poly(meth)acrylates, polystyrenes, polyacrylamides, polyvinyl alcohol, polyvinyl acetate, polyesters, polyurethanes, polyethylene, polypropylene, polylactic acid, polyacrylonitrile, polyvinyl ethers, derivatives thereof, salts thereof, copolymers thereof, or240878W001 combinations thereof. For example, the polymer is selected from the group consisting of polymethyl methacrylate, polyethyl methacrylate, poly(n-butyl methacrylate), polystyrene, poly(chloro-styrene), poly (alpha-methyl styrene), poly(N-methylolacrylamide), styrene / methyl methacrylate copolymer, polyalkylated acrylate, polyhydroxyl acrylate, polyamino acrylate, polycyanoacrylate, polyfluorinated acrylate, poly(N-methylolacrylamide), polyacrylic acid, polymethacrylic acid, methyl methacrylate / ethyl acrylate / acrylic acid copolymer, styrene / methyl methacrylate / acrylic acid copolymer, polyvinyl acetate, polyvinylpyrrolidone, polyvinylcaprolactone, polyvinylcaprolactam, a co-polymer of methyl methacrylate and [2- (methacryloyloxy)ethyl]trimethylammonium chloride, derivatives thereof, salts thereof, or combinations thereof.[OHl] In certain embodiments, the metal oxide material of the closed-cell metal oxide particles is selected from silica, titania, alumina, zirconia, ceria, iron oxides, zinc oxide, indium oxide, tin oxide, chromium oxide, or combinations thereof. In certain embodiments, the metal oxide comprises SiCh, TiCh, Ti20s, AI2O3, or Fe20s.

[0112] In certain embodiments, a weight to weight ratio of the metal oxide particles to the polymer particles is from about 1 / 10, about 2 / 10, about 3 / 10, about 4 / 10, about 5 / 10 about 6 / 10, about 7 / 10, about 8 / 10, about 9 / 10, to about 10 / 9, about 10 / 8, about 10 / 7, about 10 / 6, about 10 / 5, about 10 / 4, about 10 / 3, about 10 / 2, or about 10 / 1. In certain embodiments, the weight to weight ratio of the metal oxide particles to the polymer particles is 1 / 3, 2 / 3, 1 / 1, or 3 / 2.

[0113] In further embodiments, the closed-cell metal oxide particles can have, e.g., from about 60.0 wt% to about 99.9 wt% metal oxide, based on the total weight of the closed-cell metal oxide particles. In other embodiments, the closed-cell metal oxide particles comprise from about 0.1 wt% to about 40.0 wt% of one or more light absorbers, based on the total weight of the closed-cell metal oxide particles. In other embodiments, the metal oxide is from any of about 60.0 wt%, about 64.0 wt%, about 67.0 wt%, about 70.0 wt%, about 73.0 wt%, about 76.0 wt%, about 79.0 wt%, about 82.0 wt% or about 85.0 wt% to any of about 88.0 wt%, about 91.0 wt%, about 94.0 wt%, about 97.0 wt%, about 98.0 wt%, about 99.0 wt% or about 99.9 wt% metal oxide, based on the total weight of the closed-cell metal oxide particles.

[0114] In certain embodiments, the closed-cell metal oxide particles are prepared by a process comprising forming a liquid dispersion of polymer particles and metal oxide particles; forming liquid droplets of the dispersion; drying the liquid droplets to provide polymer template particles comprising polymer and metal oxide; and removing the polymer to provide closed-cell metal oxide particles. In such embodiments, the resulting closed-cells (and thus the encapsulated voids) are monodisperse.240878W001

[0115] In certain embodiments, the closed-cell metal oxide particles are prepared by a method comprising: generating liquid droplets from a particle dispersion comprising metal oxide particles and polymer particles; drying the liquid droplets to provide dried particles comprising a matrix of the metal oxide particles embedded with the polymer particles; and calcining or sintering the dried particles to densify the metal oxide particle matrix and remove the polymer particles, resulting in closed-cell metal oxide particles.

[0116] In other embodiments, the closed-cell metal oxide particles are prepared by a process comprising: generating liquid droplets from a particle dispersion comprising polymer particles and a sol-gel of a metal oxide; drying the liquid droplets to provide dried particles comprising a matrix of the metal oxide with the polymer particles; and calcining or sintering the dried particles to remove the polymer particles, resulting in closed-cell metal oxide particles. An exemplary process is described as follows: liquid droplets are generated from a particle dispersion (e.g., an aqueous particle dispersion with a pH of 3-5) comprising polymer particles and a precursor of a metal oxide. The precursor may be, for example, tetraethyl orthosilicate (TEOS) or tetramethyl orthosilicate (TMOS) as a silica precursor, titanium propoxide as a titania precursor, or zirconium acetate as a zirconium precursor. The liquid droplets are dried to provide dried particles comprising a hydrolyzed precursor of metal oxide that surrounds and coats the polymer particles. The dried particles are then heated to sinter the metal oxide via a condensation reaction of the hydrolyzed precursor, and to remove the polymer particles via calcination.

[0117] In certain embodiments, the evaporation of the liquid medium may be performed in the presence of self-assembly substrates such as conical tubes or silicon wafers. In certain embodiments, dried particle mixtures may be recovered, e.g., by filtration or centrifugation. In certain embodiments, the drying comprises microwave irradiation, oven drying, drying under vacuum, drying in the presence of a desiccant, or a combination thereof.

[0118] In certain embodiments utilizing liquid droplets, the droplets are formed with a microfluidic device. The microfluidic device can contain a droplet junction having a channel width, for example, of from any of about 10 pm, about 15 pm, about 20 pm, about 25 pm, about 30 pm, about 35 pm, about 40 pm, or about 45 pm to any of about 50 pm, about 55 pm, about 60 pm, about 65 pm, about 70 pm, about 75 pm, about 80 pm, about 85 pm, about 90 pm, about 95 pm, or about 100 pm.

[0119] In certain embodiments, generating and drying the liquid droplets is performed using a spray-drying process. In certain embodiments of spray-drying techniques, a feed of a liquid solution or dispersion is fed (e.g. pumped) to an atomizing nozzle associated with a compressed gas inlet through which a gas is injected. The feed is pumped through the atomizing nozzle 304240878W001 to form liquid droplets. The liquid droplets are surrounded by a pre-heated gas in an evaporation chamber, resulting in evaporation of solvent to produce dried particles. The dried particles are carried by the drying gas through a cyclone and deposited in a collection chamber. Gases include nitrogen and / or air. In an embodiment of an exemplary spray-drying process, a liquid feed contains a water or oil phase, the metal oxide, and the polymer particles. The dried particles comprise a self-assembled structure of each polymer particle surrounded by metal oxide particles.

[0120] Air may be considered a continuous phase with a dispersed liquid phase (a liquid-ingas emulsion). In certain embodiments, spray-drying comprises an inlet temperature of from any of about 100°C, about 105°C, about 110°C, about 115°C, about 120°C, about 130°C, about 140°C, about 150°C, about 160°C, or about 170°C to any of about 180°C, about 190°C, about 200°C, about 210°C, about 215°C, or about 220°C. In certain embodiments a pump rate (feed flow rate) of from any of about 1 mL / min, about 2 mL / min, about 5 mL / min, about 6 mL / min, about 8 mL / min, about 10 mL / min, about 12 mL / min, about 14 mL / min, or about 16 mL / min to any of about 18 mL / min, about 20 mL / min, about 22 mL / min, about 24 mL / min, about 26 mL / min, about 28 mL / min, or about 30 mL / min is utilized.

[0121] In certain embodiments, vibrating nozzle techniques may be employed. In such techniques, a liquid dispersion is prepared, and then droplets are formed and dropped into a bath of a continuous phase. The droplets are then dried. Vibrating nozzle equipment may comprise, for example, a syringe pump and a pulsation unit. Vibrating nozzle equipment may also comprise a pressure regulation valve.

[0122] In certain embodiments, polymer removal may be performed, for example, via calcination, pyrolysis, or with a solvent (solvent removal). Calcination is performed in certain embodiments at temperatures of at least about 200°C, at least about 500°C, at least about 1000°C, from about 200°C to about 1200°C, or from about 200°C to about 700°C. The calcining can be for a suitable period, e.g., from about 0.1 hour to about 12 hours or from about 1 hour to about 8.0 hours. In other embodiments, the calcining can be for at least about 0.1 hour, at least about 1 hour, at least about 5 hours, or at least about 10 hours. In other embodiments, the calcining can be from any of about 200°C, about 350°C, about 400°C, 450°C, about 500°C or about 550°C to any of about 600°C, about 650°C, about 700°C, or about 1200°C for a period of from any of about 0.1 h (hour), about 1 h, about 1.5 h, about 2.0 h, about 2.5 h, about 3.0 h, about 3.5 h, or about 4.0 h to any of about 4.5 h, about 5.0 h, about 5.5 h, about 6.0 h, about 6.5 h, about 7.0 h, about 7.5 h about 8.0 h, or about 12 h. While the polymer is removed during240878W001 this process, an array of void volumes will be substantially maintained by the closed-cells left behind after the calcination.

[0123] In certain embodiments, a particle size ratio of the metal oxide particles to the polymer particles is from 1 / 50 to 1 / 5 (e.g., 1 / 10).

[0124] In certain embodiments, the metal oxide particles have an average diameter of from about 1 nm, about 5 nm, about 10 nm, about 15 nm, about 20 nm, about 25 nm, about 30 nm, about 35 nm, about 40 nm, about 45 nm, about 50 nm, about 55 nm, or about 60 nm to about 65 nm, about 70 nm, about 75 nm, about 80 nm, about 85 nm, about 90 nm, about 95 nm, about 100 nm, about 105 nm, about 110 nm, about 115 nm, or about 120 nm. In other embodiments, the matrix nanoparticles have an average diameter of about 5 nm to about 150 nm, about 50 to about 150 nm, or about 100 to about 150 nm.

[0125] In certain embodiments, the polymer particles have an average diameter of from about 50 nm to about 990 nm. In other embodiments, the particles have an average diameter of from any of about 50 nm, about 75 nm, about 100 nm, about 130 nm, about 160 nm, about 190 nm, about 210 nm, about 240 nm, about 270 nm, about 300 nm, about 330 nm, about 360 nm, about 390 nm, about 410 nm, about 440 nm, about 470 nm, about 500 nm, about 530 nm, about 560 nm, about 590 nm, or about 620 nm to any of about 650 nm, about 680 nm, about 710 nm, about 740 nm, about 770 nm, about 800 nm, about 830 nm, about 860 nm, about 890 nm, about 910 nm, about 940 nm, about 970 nm, or about 990 nm.

[0126] In certain embodiments, removing the polymer particles comprises calcination, pyrolysis, or solvent removal. The calcining of the polymer particles can be, e.g., at temperatures of from about 300°C to about 800°C for a period of from about 1 hour to about 8 hours.

[0127] In certain embodiments, the closed-cell metal oxide particles comprise mainly metal oxide, that is, they may consist essentially of or consist of metal oxide. Advantageously, depending on the particle compositions, relative sizes, and shapes of the metal oxide particles used, a bulk sample of the closed-cell metal oxide particles may exhibit color observable by the human eye, may appear white, or may exhibit properties in the UV spectrum. A light absorber may also be present within (e.g., encapsulated by or embedded within) the particles or physically mixed with the particles, such as a UV-absorbing compound. Absorbers include inorganic and organic materials, for example, a broadband absorber such as carbon black. Absorbers may, for example, be added by physically mixing the particles and the absorbers together or by including the absorbers in the droplets to be dried.240878W001

[0128] Angle-dependent optical properties may be achieved, for example, with the use of monodisperse polymer particles. Angle-dependent optical properties may also be achieved when a step of drying the liquid droplets is performed slowly, allowing the particles to become ordered. Angle-independent optical properties may be achieved when a step of drying the liquid droplets is performed quickly, not allowing the particles to become ordered.

[0129] In certain embodiments, the metal oxide particles can comprise combinations of different types of particles. For example, the metal oxide particles may be a mixture of two different metal oxides (i.e., discrete distributions of metal oxide particles), such as a mixture of alumina particles and silica particles with each species being characterized by the same or similar size distributions.

[0130] In certain embodiments, the metal oxide particles may comprise more complex compositions and / or morphologies. For example, the metal oxide particles may comprise particles such that each individual particle comprises two or more metal oxides (e.g., silica- titania particles). Such particles may comprise, for example, a mixture of two or more metal oxides.

[0131] In certain embodiments, the metal oxide particles and / or the polymer particles may comprise surface functionalization. An example of a surface functionalization is a silane coupling agent (e.g., silane-functionalized silica). In certain embodiments, the surface functionalization is performed on the metal oxide particles prior to self-assembly and densifi cation. In certain embodiments, the surface functionalization is performed on the closedcell metal oxide particles after densification. In certain embodiments, the surfacefunctionalization may be selected to impart a net positive or net negative surface charge to the particles when dispersed in an aqueous solution.

[0132] To obtain reflectance over a wide spectral range, more than one type (a blend) of closed-cell metal oxide particles can be incorporated in the coating compositions. A combination of two closed-cell metal oxide particles can increase the spectral range over which reflectance is observed. In certain embodiments, the closed-cell metal oxide particles exhibit an ability to disperse well into the coating compositions and thus uniformly coat a surface. In particular, the closed-cell metal oxide particles are compatible with all types of solvent and coating systems such as acrylics and styrene-acrylic systems.1.3 Hybrid Metal Oxide Particles

[0133] Certain embodiments relate to coating compositions that incorporate hybrid metal oxide particles as photonic particles, which are particles that comprise a metal oxide matrix in240878W001 which is embedded a template of spherical nanoparticles comprised of another metal oxide as shown in FIG. 1. Hybrid metal oxide particles have physical parameters that can be tuned to enhance performance properties of their corresponding coating compositions. By way of example, and not to be considered limiting, physical parameters that can be adjusted include the particle size diameters, particle size distributions, particle shapes, occlusion diameter within the particles, porosity, packing density, surface texture, and the degree of order with regard to the spatial arrangement of the occlusions in the particles. Chemical parameters that can be adjusted include the chemical make-up of the particles, including the composition of the matrix and surface functionalizations. When used in coating compositions, the particles can be added in a sufficient amount to enhance reflective properties and optionally replace existing components such as pigments and / or fillers in the coating compositions. The terms “tuned,” “adjusted,” and “configured” can be used interchangeably and refer to an adjustment to a physical and / or chemical parameter of the particles to change their reflectance properties. The hybrid metal oxide particles described herein can exhibit high stability and thus can be formulated into coating compositions as a replacement for less stable and / or less environmentally friendly components.

[0134] In certain embodiments, the hybrid metal oxide particles are produced by drying droplets of a formulation comprising a matrix of first metal oxide particles (referred to as “matrix” nanoparticles) on the order of 1 to 120 nm in diameter, and second metal oxide nanoparticles (e.g., spherical nanoparticles) on the order of 50 to 999 nm which will form the template (referred to as “template” nanoparticles). In certain embodiments, a spray drying or microfluidics process is used to generate the droplets (e.g., aqueous droplets), and the droplets are dried to remove their solvent. In certain embodiments that utilize a spray drying process, the generation of droplets and drying is performed in rapid succession. During the drying process, the template nanoparticles (metal oxide A of FIG. 3) self-assemble to form a microsphere containing a discrete matrix of metal oxide B particles in which are embedded the template nanoparticles of metal oxide A. The dried particles are then heated under conditions suitable for forming a continuous matrix from the metal oxide B particles in which the metal oxide A particles are embedded. For example, by sintering the matrix nanoparticles (which may contain multiple metal oxides) in a muffle furnace, the matrix nanoparticles densify and form a stable, continuous matrix with the template nanoparticles being retained within the structure. In certain embodiments, the droplets further contain a binder (e.g., a material selected from boehmite, alumina sol, silica sol, titania sol, zirconium acetate, ceria sol, or combinations thereof). The dried droplets are then heated under conditions suitable to cause the binder and the metal oxide B particles to form the continuous matrix (e.g., at a temperature of about 300°C to about 800°C for240878W001 a period of about 1 hour to about 8 hours). This final structure is a substantially non-porous solid particle.

[0135] Advantageously, the architecture of hybrid metal oxide particles prevents media infiltration into the interior of the particles. The retention of the template in the hybrid metal oxide particles helps to ensure that the media cannot infiltrate the structure as it would the voids of the porous metal oxide particle. Preventing infiltration of polymers, large molecules, or other viscous materials frequently used in such coating formulations maintains a constant net refractive index between the matrix and the embedded “occlusions” (regions of different metal oxide composition formed by the template nanoparticles) regardless of the surrounding media in the application.

[0136] Depending upon the physical parameters of the hybrid metal oxide particles, they can have a broad range of uses in coating compositions. The hybrid metal oxide particles can be synthesized as to adjust (1) the hybrid metal oxide particles diameter, (2) the template nanoparticle metal oxide composition, (3) the matrix nanoparticle metal oxide composition, (4) the diameter of the template nanoparticle metal oxide occlusions within the matrix nanoparticles, (5) the degree of order with regard to the spatial arrangement of the occlusions in the hybrid metal oxide particles, and (6) the average distance between the occlusions (template nanoparticles). When used in coating compositions, the hybrid metal oxide particles can be added as such to enhance existing properties and / or replace existing components in the coating.

[0137] An additional benefit of the hybrid metal oxide particles is the capability to add materials into the metal oxide occlusions. Since these occlusions are typically retained in the structure of the hybrid metal oxide particles, a material which enhances or imparts a desired effect (for example, a light absorber) can be incorporated into the template and be retained within the structure.

[0138] Hybrid metal oxide particles may be produced, for example, as described in International Application No. PCT / IB2021 / 000485, filed on July 21, 2021, the disclosure of which is hereby incorporated by reference herein in its entirety. Hybrid metal oxide particles may be prepared according to various methods, including, but not limited to: (1) methods utilizing colloidal metal oxide matrix particles and colloidal metal oxide template particles; (2) methods utilizing colloidal metal oxide matrix particles, colloidal metal oxide template particles, and binder particles; (3) binder particles alone or binder particles in combination with colloidal metal oxide template particles; and (4) colloidal metal oxide template particles in combination with a sol-gel synthesized metal oxide matrix.240878W001

[0139] Method (1) utilizes metal oxide template particles embedded in discrete metal oxide matrix particles. The structure can be sintered, fusing the matrix particles into a continuous matrix of metal oxide.

[0140] Method (2) utilizes metal oxide template and matrix particles in combination with binder particles. The template particles are embedded in a matrix comprising discrete metal oxide matrix particles and binder particles. The structure is heated resulting in a reaction of the binder particles, which results in the formation of a continuous matrix in which are embedded the metal oxide template particles. In an illustrative example, silica particles are used as the template particles, alumina particles are used as the matrix particles, and boehmite is used as the binder particles. The silica template is embedded in a matrix of alumina and boehmite. The structure is heated to a temperature sufficient to dehydrate the boehmite into alumina, forming a continuous matrix of alumina. If different metal oxide template particles were used, such as titania, the result would be a continuous matrix comprising discrete particles of titania embedded in continuous alumina.

[0141] Method (3) utilizes binder particles alone or metal oxide template particles in combination with binder particles. A template of binder particles or colloidal metal oxide particles are embedded in a matrix of binder particles. The structure is heated resulting in a reaction of the binder particles, which results in the formation of a continuous matrix of metal oxide template particles or reacted binder particles.

[0142] Method (4) utilizes sol-gel synthesis of a metal oxide matrix. The template particles are dispersed in a solution of a metal oxide precursor, such as a metal alkoxide. Hydrolysis of the metal oxide precursor forms an intermediate that serves as a matrix in which the template particles are embedded. The structure is then heated to undergo hydrolysis and condensation of the matrix, resulting in the formation of a continuous matrix of metal oxide. In an illustrative example, alumina template particles are initially dispersed in a solution of tetraethyl orthosilicate (TEOS). Heating converts the TEOS to silica, resulting in the formation of a continuous matrix of silica in which the alumina template particles are embedded.

[0143] The resulting hybrid metal oxide particles may be micron-scaled, for example, having average diameters from about 0.5 pm to about 50 pm. In certain embodiments, the hybrid metal oxide particles have an average diameter from about 0.5 pm, about 0.6 pm, about 0.7 pm, about 0.8 pm, about 0.9 pm, about 1.0 pm, about 5.0 pm, about 10 pm, about 20 pm, about 30 pm, about 40 pm, about 50 pm, or within any range defined by any of these average diameters (e.g., about 1.0 pm to about 20 pm, about 5.0 pm to about 50 pm, etc.). The metal oxide employed may also be in particle form, and the particles may be nano-scaled. The metal oxide matrix240878W001 nanoparticles may have an average diameter, for example, of about 1 nm to about 120 nm. The metal oxide template nanoparticles may have an average diameter, for example, of about 50 nm to about 999 nm. One or more of the template nanoparticles or the matrix nanoparticles may be polydisperse or monodisperse. In certain embodiments, either metal oxide may be provided as metal oxide particles or may be formed from a metal oxide precursor, for example, via a sol-gel technique. An exemplary sol-gel process is described as follows: liquid droplets are generated from a particle dispersion (e.g., an aqueous particle dispersion with a pH of 3-5) comprising metal oxide template nanoparticles and a precursor of a metal oxide. The precursor may be, for example, TEOS or tetramethyl orthosilicate (TMOS) as a silica precursor, titanium propoxide as a titania precursor, or zirconium acetate as a zirconium precursor. The liquid droplets are dried to provide dried particles comprising a hydrolyzed precursor of metal oxide that surrounds and coats the metal oxide template nanoparticles.

[0144] Certain embodiments of the hybrid metal oxide particles exhibit color in the visible spectrum at a wavelength range selected from the group consisting of 380 nm to 450 nm, 451 nm to 495 nm, 496 nm to 570 nm, 571 nm to 590 nm, 591 nm to 620 nm, 621 nm to 750 nm, 751 nm to 800 nm, and any range defined therebetween (e.g., 496 nm to 620 nm, 450 nm to 750 nm, etc.). In certain embodiments, the particles exhibit a wavelength range in the ultraviolet spectrum selected from the group consisting of 100 nm to 400 nm, 100 nm to 200 nm, 200 nm to 300 nm, and 300 nm to 400 nm.

[0145] In certain embodiments, the hybrid metal oxide particles are non-porous or substantially non-porous. In certain embodiments, the hybrid metal oxide particles can have, for example, an average diameter of from about 0.5 pm to about 100 pm. In other embodiments, the particles can have, for example, an average diameter of from about 1 pm to about 75 pm.

[0146] In certain embodiments, the hybrid metal oxide particles have an average diameter, for example, of from about 1 pm to about 75 pm, from about 2 pm to about 70 pm , from about 3 pm to about 65 pm , from about 4 pm to about 60 pm, from about 5 pm to about 55 pm, or from about 5 pm to about 50 pm; for example, from any of about 5 pm, about 6 pm, about 7 pm, about 8 pm, about 9 pm, about 10 pm, about 11 pm, about 12 pm, about 13 pm, about 14 pm, or about 15 pm to any of about 16 pm, about 17 pm, about 18 pm, about 19 pm, about 20 pm, about 21 pm, about 22 pm, about 23 pm, about 24 pm, or about 25 pm. Other embodiments can have an average diameter of from any of about 4.5 pm, about 4.8 pm, about 5.1 pm, about 5.4 pm, about 5.7 pm, about 6.0 pm, about 6.3 pm, about 6.6 pm, about 6.9 pm, about 7.2 pm, or about 7.5 pm to any of about 7.8 pm about 8.1 pm, about 8.4 pm, about 8.7 pm, about 9.0 pm, about 9.3 pm, about 9.6 pm, or about 9.9 pm.240878W001

[0147] In certain embodiments, the hybrid metal oxide particles can have, for example, an average diameter of from any of about 4.5 pm, about 4.8 pm, about 5.1 pm, about 5.4 pm, about 5.7 pm, about 6.0 pm, about 6.3 pm, about 6.6 pm, about 6.9 pm, about 7.2 pm, or about 7.5 pm to any of about 7.8 pm about 8.1 pm, about 8.4 pm, about 8.7 pm, about 9.0 pm, about 9.3 pm, about 9.6 pm, or about 9.9 pm.

[0148] In certain embodiments, the metal oxide materials of the hybrid metal oxide particles are independently selected from silica, titania, alumina, zirconia, ceria, iron oxides, zinc oxide, indium oxide, tin oxide, chromium oxide, or combinations thereof. In certain embodiments, the metal oxide are selected from SiCh, TiCh, Ti20s, AI2O3, or Fe20s. As an example, the matrix metal oxide comprises titania, and the template nanoparticles (occlusions) comprise silica.

[0149] In certain embodiments, a weight to weight ratio of the first metal oxide particles to the second metal oxide particles is from about 1 / 10, about 2 / 10, about 3 / 10, about 4 / 10, about 5 / 10 about 6 / 10, about 7 / 10, about 8 / 10, about 9 / 10, to about 10 / 9, about 10 / 8, about 10 / 7, about 10 / 6, about 10 / 5, about 10 / 4, about 10 / 3, about 10 / 2, or about 10 / 1. In certain embodiments, the weight to weight ratio is 2 / 3 or 3 / 2.

[0150] In certain embodiments, a particle size ratio of the metal oxide matrix particles to the metal oxide template particles is from 1 / 20 to 1 / 5 (e.g., 1 / 10).

[0151] In certain embodiments, the matrix nanoparticles have an average diameter of from about 1 nm, about 5 nm, about 10 nm, about 15 nm, about 20 nm, about 25 nm, about 30 nm, about 35 nm, about 40 nm, about 45 nm, about 50 nm, about 55 nm, or about 60 nm to about 65 nm, about 70 nm, about 75 nm, about 80 nm, about 85 nm, about 90 nm, about 95 nm, about 100 nm, about 105 nm, about 110 nm, about 115 nm, or about 120 nm. In other embodiments, the matrix nanoparticles have an average diameter of about 5 nm to about 150 nm, about 50 to about 150 nm, or about 100 to about 150 nm.

[0152] In certain embodiments, the occlusions (template nanoparticles) have an average diameter of from about 100 nm, about 150 nm, about 200 nm, about 250 nm, or about 300 nm to about 350 nm, about 400 nm, about 450 nm, about 500 nm, about 550 nm, or about 600 nm.

[0153] In certain embodiments, the hybrid metal oxide particles can have, for example, from about 60.0 wt% to about 99.9 wt% metal oxide, based on the total weight of the hybrid metal oxide particles. In other embodiments, the structural colorants comprise from about 0.1 wt% to about 40.0 wt% of one or more light absorbers, based on the total weight of the hybrid metal oxide particles. In other embodiments, the metal oxide is from any of about 60.0 wt%, about 64.0 wt%, about 67.0 wt%, about 70.0 wt%, about 73.0 wt%, about 76.0 wt%, about 79.0 wt%, about 82.0 wt%, or about 85.0 wt% to any of about 88.0 wt%, about 91.0 wt%, about 94.0 wt%,240878W001 about 97.0 wt%, about 98.0 wt%, about 99.0 wt%, or about 99.9 wt% metal oxide, based on the total weight of the hybrid metal oxide particles.

[0154] In certain embodiments, the hybrid metal oxide particles are prepared by a method comprising: generating liquid droplets from a particle dispersion comprising first metal oxide particles (e.g., matrix nanoparticles) and second metal oxide particles (e.g., template nanoparticles); drying the liquid droplets to provide dried particles comprising a matrix of the first metal oxide particles embedded with the second metal oxide particles; and sintering the dried particles to densify the matrix and obtain the hybrid metal oxide particles.

[0155] In certain embodiments, a liquid dispersion is first formed, for example, by mixing the first metal oxide particles (e.g., matrix nanoparticles) and the second metal oxide particles (e.g., template nanoparticles) in a liquid medium. In certain embodiments, the liquid dispersion is an aqueous dispersion, an oil dispersion, or a combination thereof.

[0156] In certain embodiments, the hybrid metal oxide particles may be recovered, for example, by filtration or centrifugation. The recovered particles may then be placed on a substrate, for example, and dried by evaporating the liquid medium. In certain embodiments, the drying comprises microwave irradiation, oven drying, drying under vacuum, drying in the presence of a desiccant, or a combination thereof to evaporate the liquid medium. In certain embodiments, the evaporation of the liquid medium may be performed in the presence of selfassembly substrates such as conical tubes or silicon wafers.

[0157] In certain embodiments utilizing liquid droplets, the droplets are formed with a microfluidic device. The microfluidic device can contain a droplet junction having a channel width, for example, of from any of about 10 pm, about 15 pm, about 20 pm, about 25 pm, about 30 pm, about 35 pm, about 40 pm, or about 45 pm to any of about 50 pm, about 55 pm, about 60 pm, about 65 pm, about 70 pm, about 75 pm, about 80 pm, about 85 pm, about 90 pm, about 95 pm, or about 100 pm.

[0158] In certain embodiments, generating and drying the liquid droplets is performed using a spray-drying process. In certain embodiments of spray-drying techniques, a feed of a liquid solution or dispersion is fed (e.g. pumped) to an atomizing nozzle associated with a compressed gas inlet through which a gas is injected. The feed is pumped through the atomizing nozzle to form liquid droplets. The liquid droplets are surrounded by a pre-heated gas in an evaporation chamber, resulting in evaporation of solvent to produce dried particles. The dried particles are carried by the drying gas through a cyclone and deposited in a collection chamber. Gases include nitrogen and / or air. In an embodiment of an exemplary spray-drying process, a liquid feed contains a water or oil phase, metal oxide matrix particles, and metal oxide template240878W001 particles. The dried particles comprise a self-assembled structure of arrayed metal oxide template particles embedded in metal oxide matrix particles.

[0159] Air may be considered a continuous phase with a dispersed liquid phase (a liquid-ingas emulsion). In certain embodiments, spray-drying comprises an inlet temperature of from any of about 100°C, about 105°C, about 110°C, about 115°C, about 120°C, about 130°C, about 140°C, about 150°C, about 160°C, or about 170°C to any of about 180°C, about 190°C, about 200°C, about 210°C, about 215°C, or about 220°C. In certain embodiments a pump rate (feed flow rate) of from any of about 1 mL / min, about 2 mL / min, about 5 mL / min, about 6 mL / min, about 8 mL / min, about 10 mL / min, about 12 mL / min, about 14 mL / min, or about 16 mL / min to any of about 18 mL / min, about 20 mL / min, about 22 mL / min, about 24 mL / min, about 26 mL / min, about 28 mL / min, or about 30 mL / min is utilized.

[0160] In certain embodiments, vibrating nozzle techniques may be employed. In such techniques, a liquid dispersion is prepared, and then droplets are formed and dropped into a bath of a continuous phase. The droplets are then dried. Vibrating nozzle equipment may comprise, for example, a syringe pump and a pulsation unit. Vibrating nozzle equipment may also comprise a pressure regulation valve.

[0161] In certain embodiments, the dried hybrid metal oxide particles are subjected to sintering. The sintering can be performed at temperatures of from about 300°C to about 800°C for a period of from about 1 hour to about 8 hours. In certain embodiments, if the template nanoparticles are monodisperse and ordered within the dried hybrid metal oxide particles prior to sintering, the ordered arrangement of the template nanoparticles may be substantially preserved in the hybrid metal oxide particles after sintering.

[0162] In certain embodiments, the hybrid metal oxide particles comprise mainly metal oxide, that is, they may consist essentially of or consist of metal oxide. Advantageously, depending on the particle compositions, relative sizes, and shapes of the metal oxide particles used, a bulk sample of the hybrid metal oxide particles may exhibit color observable by the human eye, may appear white, or may exhibit properties in the UV spectrum. A light absorber may also be present within (e.g., encapsulated by or embedded within) the particles or physically mixed with the particles, such as a UV-absorbing compound. Absorbers include inorganic and organic materials, for example, a broadband absorber such as carbon black. Absorbers may, for example, be added by physically mixing the particles and the absorbers together or by including the absorbers in the droplets to be dried.

[0163] Angle-dependent optical properties may be achieved, for example, with the use of monodisperse metal oxide particles (e.g., template particles in the present embodiments). Angle-240878W001 dependent optical properties may also be achieved when a step of drying the liquid droplets is performed slowly, allowing the particles to become ordered. Angle-independent optical properties may be achieved when a step of drying the liquid droplets is performed quickly, not allowing the particles to become ordered.

[0164] In certain embodiments, the first metal oxide particles and / or the second metal oxide particles can comprise combinations of different types of particles. For example, the first metal oxide particles may be a mixture of two different metal oxides (i.e., discrete distributions of metal oxide particles), such as a mixture of alumina particles and silica particles with each species being characterized by the same or similar size distributions.

[0165] In certain embodiments, the first metal oxide particles and / or the second metal oxide particles may comprise more complex compositions and / or morphologies. For example, the first metal oxide particles may comprise particles such that each individual particle comprises two or more metal oxides (e.g., silica-titania particles). Such particles may comprise, for example, an amorphous mixture of two or more metal oxides or may have a core-shell configuration (e.g., titania-coated silica particles, polymer-coated silica, carbon black-coated silica, etc.).

[0166] In certain embodiments, the first metal oxide particles and / or the second metal oxide particles may comprise surface functionalization. An example of a surface functionalization is a silane coupling agent (e.g., silane-functionalized silica). In certain embodiments, the surface functionalization is performed on the first metal oxide particles and / or the second metal oxide particles prior to self-assembly and densification. In certain embodiments, the surface functionalization is performed on the hybrid metal oxide particles after densification.

[0167] To obtain reflectance over a wide spectral range, more than one type (a blend) of hybrid metal oxide particles can be incorporated in the coating compositions. A combination of two hybrid metal oxide particles can increase the spectral range over which reflectance is observed. In certain embodiments, the hybrid metal oxide particles exhibit an ability to disperse well into the coating compositions and thus uniformly coat a surface. In particular, the hybrid metal oxide particles are compatible with all types of solvent and coating systems such as acrylics and styrene-acrylic systems.

[0168] In certain embodiments, the hybrid metal oxide particles can have an average occlusion diameter of 200 nm or greater, 250 nm or greater, 300 nm or greater, 350 nm or greater, 400 nm or greater, 450 nm or greater, 500 nm or greater, 550 nm or greater, 600 nm or greater, 650 nm or greater, 700 nm or greater, 750 nm or greater, or up to 800 nm or greater. In certain embodiments, the hybrid metal oxide particles can have an average occlusion diameter of 800 nm or less, 750 nm or less, 700 nm or less, 650 nm or less, 600 nm or less, 550 nm or less,240878W001500 nm or less, 450 nm or less, 400 nm or less, 350 nm or less, 300 nm or less, 250 nm or less, or 200 nm or less. The hybrid metal oxide particles can have an average occlusion diameter from any of the minimum values to any of the maximum values described above of the hybrid metal oxide particles. For example, the hybrid metal oxide particles can have an average occlusion diameter of from 200 nm to 800 nm, from 200 nm to 600 nm, from 200 nm to 400 nm, from 250 nm to 400 nm, or from 250 nm to 350 nm.

[0169] As discussed herein, the average occlusion size of the hybrid metal oxide particles can vary, depending on the size of the template metal oxide particles used. However, spherical monodispersed template metal oxide particles can be employed to create a substantially uniform and unimodal distribution of occlusion sizes. In other cases, a multimodal distribution of template metal oxide particles can be employed to create a multimodal distribution, such as a bimodal distribution, of occlusion sizes. In general, however, the occlusion size of the hybrid metal oxide particles is nano-scaled, such as from about 200 nm to about 400 nm. While the occlusion size significantly influences the optical properties exhibited by the particles, the shape and size distribution of occlusions as well as of the hybrid metal oxide particles can affect the optical properties.Clear Coat Embodiments Comprising Photonic Particles

[0170] Exemplary coating compositions can be formed, e.g., by combining the photonic particles with water and at least one water-miscible film-forming binder to form an aqueous clear coat coating composition.

[0171] The at least one water-miscible film-forming binder may be dissolved or dispersed in an aqueous medium. Nonlimiting examples of suitable water-miscible film-forming binders may include polyurethane resins, acrylated polyurethane resins, poly(meth)acrylate polymers (acrylic polymers), polyester resins, acrylated polyester resins, polyether resins and alkyd resins. The aqueous coating composition may also include a binder system including more than one water- miscible film-forming binder.

[0172] The at least one water-miscible film-forming binder may be physically dried and / or chemically crosslinked, for example by polymerization, polycondensation, and / or polyaddition reactions. Chemically cross-linkable water-miscible film-forming binders may contain corresponding cross-linkable functional groups. Suitable functional groups may include, for example, hydroxyl groups, carbamate groups, isocyanate groups, acetoacetyl groups, unsaturated groups, for example, (meth)acryloyl groups, epoxide groups, carboxyl groups, and amino groups. The at least one water-miscible film-forming binder may be paired with or include a crosslinking240878W001 agent. The crosslinking agent may include a complementarily-reactive functional group that may provide crosslinking during curing. For example, hydroxyl group-containing polymers and aminoplast (e.g., melamine) crosslinking agents may be used with chemically crosslinkable water-miscible film-forming binders.

[0173] Embodiments including aminoplast crosslinking agents may further include a strong acid catalyst to enhance curing of the aqueous coating composition. Such catalysts may include, for example, para-toluenesulfonic acid, dinonylnaphthalene disulfonic acid, dodecylbenzenesulfonic acid, phenyl acid phosphate, monobutyl maleate, butyl phosphate, and hydroxy phosphate ester. Strong acid catalysts may also be blocked, e.g., with an amine.

[0174] The at least one water-miscible film-forming binder may include ionic and / or nonionic groups such as carboxyl groups and polyethylene oxide segments. Suitable neutralizing agents for the carboxyl groups are basic compounds, such as tertiary amines, for example, triethylamine, dimethylethanolamine, and diethylethanolamine. Alternatively or additionally, the aqueous coating composition may also include one or more external emulsifiers. The external emulsifier(s) may disperse the water-miscible film-forming binder within the aqueous coating composition.

[0175] In one non-limiting example, the water-miscible film-forming binder is an aqueous polyurethane dispersion. The aqueous polyurethane dispersion may be prepared by emulsifying hydrophobic polyurethanes in water with the aid of one or more external emulsifiers. The aqueous polyurethane dispersion may also be prepared to be self-dispersible by incorporating hydrophilic groups. One technique for imparting water-miscibility or -dispersibility may include converting carboxylate groups into anionic groups using an amine to form an anionic, polyurethane dispersion. Another technique for imparting water-miscibility may include first reacting tertiary amino alcohols with prepolymers which contain free isocyanate functionality, and then neutralizing the reaction product with an acid to form a cationic polyurethane dispersion. A further technique may include modifying prepolymers having free isocyanate functions with water-soluble long-chain polyethers to form a nonionic polyurethane dispersion.

[0176] The aqueous coating composition may alternatively include a hybrid polyurethanepolyacrylate dispersion as the water-miscible film-forming binder. The hybrid polyurethanepolyacrylate dispersion may be prepared by emulsion-polymerizing a vinylpolymer, i.e., a polyacrylate, in an aqueous polyurethane dispersion. Alternatively, the hybrid polyurethanepolyacrylate dispersion may be prepared as a secondary dispersion.

[0177] The aqueous coating composition may include the photonic particles in an amount of from about 0.01 part by weight to about 60 parts by weight, e.g., from about 1.0 part by weight240878W001 to about 20 parts by weight, based on 100 parts by weight of the water-miscible film-forming binder. That is, blending may include adding to water from about 30 parts by weight photonic particles to about 50 parts by weight photonic particles based on 100 parts by weight of the at least one water-miscible film-forming binder.

[0178] The aqueous coating composition may further include a rheology control agent and / or film-forming agent such as a colloidal layered silicate. For example, the colloidal layered silicate may provide the aqueous coating composition with stability and adjust a thixotropic shear-sensitive viscosity of the aqueous coating composition. The colloidal layered silicate may be synthetically manufactured from an inorganic mineral and may have a colloidal, gel, or sol form. A suitable colloidal layered silicate is commercially available under the trade name Laponite® from the Byk-Chemie GmbH of Wesel, Germany. Therefore, the method may further include blending the colloidal layered silicate, the passivated pigment slurry, water, and the at least one water-miscible film-forming binder to form the aqueous coating composition.

[0179] The aqueous coating composition may also include other pigments and fillers. Nonlimiting examples of other pigments and fillers may include inorganic pigments such as titanium dioxide, barium sulfate, carbon black, ocher, sienna, umber, hematite, limonite, red iron oxide, transparent red iron oxide, black iron oxide, brown iron oxide, chromium oxide green, strontium chromate, zinc phosphate, silicas such as fumed silica, calcium carbonate, talc, barytes, ferric ammonium, ferrocyanide (Prussian blue), and ultramarine, and organic pigments such as metallized and non-metallized azo reds, quinacridone reds and violets, perylene reds, copper phthalocyanine blues and greens, carbazole violet, monoarylide and diarylide yellows, benzimidazolone yellows, tolyl orange, naphthol orange, nanoparticles based on silicon dioxide, and aluminum oxide or zirconium oxide. The additional pigments can also include one or more flake-like pigments such as aluminum flakes or mica-based flakes.

[0180] The pigments may be dispersed in a resin or polymer or may be present in a pigment system which includes a pigment dispersant, such as the water-miscible film-forming binder resins of the kind already described. The pigment and dispersing resin, polymer, or dispersant may be brought into contact under a shear sufficient to break any agglomerated pigment down to primary pigment particles and to wet a surface of the pigment particles with the dispersing resin, polymer, or dispersant. The breaking of the agglomerates and wetting of the primary pigment particles may provide pigment stability and robust color.

[0181] The pigments and fillers may be present in the aqueous coating composition in an amount of less than or equal to about 60 parts by weight based on 100 parts by weight of the aqueous coating composition. For example, the pigments and fillers may be present in the240878W001 aqueous coating composition in an amount of from about 0.5 parts by weight to 50 parts by weight, or from about 1 part by weight to about 30 parts by weight, or from about 2 parts by weight to about 20 parts by weight, or from about 2.5 parts by weight to about 10 parts by weight, based on 100 parts by weight of the aqueous coating composition. The amount of pigments and fillers present in the aqueous coating composition may be selected according to a make-up or nature of the pigment, on a depth of desired color of the cured film formed from the aqueous coating composition, on an intensity of a metallic and / or pearlescent effect of the cured film, and / or on a dispersibility of the pigment.

[0182] The aqueous coating composition may also include additive components such as, but not limited to, surfactants, stabilizers, dispersing agents, adhesion promoters, ultraviolet light absorbers, hindered amine light stabilizers, benzotriazoles or oxalanilides, free-radical scavengers, slip additives, defoamers, reactive diluents, wetting agents such as siloxanes, fluorine compounds, carboxylic monoesters, phosphoric esters, polyacrylic acids and their copolymers, for example polybutyl acrylate and polyurethanes, adhesion promoters such as tricyclodecanedimethanol, flow control agents, film-forming assistants such as cellulose derivatives, and rheology control additives such as inorganic phyllosilicates such as aluminummagnesium silicates, sodium-magnesium, and sodium-magnesium-fluorine-lithium phyllosilicates of the montmorillonite type. The aqueous coating composition 14 may include one or a combination of such additives.

[0183] Exemplary hindered amine light stabilizers can include, but are not limited to, 1- cyclohexyloxy-2,2,6,6-tetramethyl-4-octadecylaminopiperidine; bis(2, 2,6,6- tetramethylpiperidin-4-yl) sebacate; bis(l-acetoxy-2,2,6,6-tetramethylpiperidin-4-yl) sebacate; bis(l,2,2,6,6-pentamethyl-4-yl) sebacate; bis(l-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl) sebacate; bis(l-octyloxy-2,2,6,6-tetramethylpiperidin-4-yl) sebacate; bis(l-acyl-2, 2,6,6- tetramethylpiperidin-4-yl) sebacate; bis(l, 2,2,6, 6-pentamethyl-4-piperidyl)-n-butyl-3,5-di-tert- butyl-4-hydroxybenzylmalonate; 2,4-bis[(l-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)- butylamino]-6-(2-hydroxyethylamino-s-triazine; bis(l -cyclohexyloxy -2, 2,6,6- tetramethylpiperidin-4-yl)-adipate; 2,4-bis[(l-cyclohexyloxy-2,2,6,6-piperidin-4-yl)- butylamino]-6-chloro-s-triazine; l-(2-hydroxy-2-methylpropoxy)-4-hydroxy-2,2,6,6- tetramethylpiperidine; l-(2-hydroxy-2-methylpropoxy)-4-oxo-2,2,6,6-tetramethylpiperidine; 1- (2-hydroxy-2-methylpropoxy)-4-octadecanoyloxy-2,2,6,6-tetramethylpiperidine; bis(l-(2- hydroxy-2-methylpropoxy)-2,2,6,6-tetramethylpiperidin-4-yl) sebacate; bis(l-(2-hydroxy-2- methylpropoxy)-2,2,6,6-tetramethylpiperidin-4-yl) adipate; 2,4-bis{N-[l-(2-hydroxy-2- methylpropoxy)-2, 2,6, 6-tetramethylpiperidin-4-yl]-N-butylamino}-6-(2 -hydroxy ethylamino)-s-240878W001 triazine; 4-benzoyl-2,2,6,6-tetramethylpiperidine; di-(l,2,2,6,6-pentamethylpiperidin-4-yl) p- methoxybenzylidenemalonate; 4-stearyloxy-2,2,6,6-tetramethylpiperidine; bis(l-octyloxy-2.2.6.6-tetramethylpiperidyl) succinate; l,2,2,6,6-pentamethyl-4-aminopiperidine; 2-undecyl- 7,7,9,9-tetramethyl-l-oxa-3,8-diaza-4-oxo-spiro[4,5]decane; tris(2,2,6,6-tetramethyl-4-piperidyl) nitrilotriacetate; tris(2-hydroxy-3-(amino-(2,2,6,6-tetramethylpiperidin-4-yl)propyl) nitrilotriacetate; tetrakis-(2,2,6,6-tetramethyl-4-piperidyl)-l,2,3,4-butane-tetracarboxylate; tetrakis-(l,2,2,6,6-pentamethyl-4-piperidyl)-l,2,3,4-butane-tetracarboxylate; 1, 1 '-(1,2- ethanediyl)-bis-(3,3,5,5-tetramethylpiperazinone); 3-n-octyl-7,7,9,9-tetramethyl-l,3,8- triazaspiro[4.5]decan-2, 4-dione; 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-l,3,8- triazaspiro[4.5]decane-2, 4-dione; 3-dodecyl-l-(2,2,6,6-tetramethyl-4-piperidyl)pyrrolidin-2,5- dione; 3-dodecyl-l-(l,2,2,6,6-pentamethyl-4-piperidyl)pyrrolidine-2,5-dione; N,N'-bis-formyl- N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine; the reaction product of 2,4- bis[(l-cyclohexyloxy-2,2,6,6-piperidin-4-yl)butylamino]-6-chloro-s-triazine with N,N'-bis(3- aminopropyl)ethylenediamine); the condensate of l-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4- hydroxypiperidine and succinic acid; linear or cyclic condensates of N,N'-bis(2, 2,6,6- tetramethyl-4-piperidyl)-hexamethylenediamine and 4-tert-octylamino-2,6-dichloro-l,3,5- triazine; linear or cyclic condensates of N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)- hexamethylenediamine and 4-cyclohexylamino-2,6-dichloro-l,3,5-triazine; linear or cyclic condensates of N,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl)-hexamethylenediamine and 4- morpholino-2,6-dichloro-l,3,5-triazine; linear or cyclic condensates of N,N'-bis-(l,2,2,6,6- pentamethyl-4-piperidyl)hexamethylenediamine and 4-morpholino-2,6-dichloro-l,3,5-triazine; the condensate of 2-chloro-4,6-bis(4-n-butylamino-2,2,6,6-tetramethylpiperidyl)-l,3,5-triazine and l,2-bis(3-aminopropylamino)ethane; the condensate of 2-chloro-4,6-di-(4-n-butylamino-1.2.2.6.6-pentamethylpiperidyl)-l,3,5-triazine and l,2-bis-(3-aminopropylamino)ethane; a reaction product of 7,7,9, 9-tetramethyl-2-cycloundecyl-l-oxa-3,8-diaza-4-oxospiro [4,5]decane and epichlorohydrin; polyfmethyl, (3-oxy-(2,2,6,6-tetramethylpiperidin-4-yl)propyl)] siloxane, CAS#182635-99-0; the reaction product of maleic acid anhydride-Cis-C22-a-olefin-copolymer with 2,2,6,6-tetramethyl-4-aminopiperidine; the oligomeric compound which is the condensation product of 4,4'-hexamethylenebis(amino-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6- [(2,2,6,6-tetramethylpiperidin-4-yl)butylamino]-s-triazine end-capped with 2-chloro-4,6- bis(dibutylamino)-s-triazine; the oligomeric compound which is the condensation product of 4,4'-hexamethylenebis(amino-l,2,2,6,6-pentamethylpiperidine) and 2,4-dichloro-6-[(l,2,2,6,6- pentaamethylpiperidin-4-yl)butylamino]-s-triazine end-capped with 2-chloro-4,6- bis(dibutylamino)-s-triazine; the oligomeric compound which is the condensation product of240878W0014,4'-hexamethylenebis(amino-l-propoxy-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-[(l- propoxy-2,2,6,6-tetramethylpiperidin-4-yl)butylamino]-s-triazine end-capped with 2-chloro-4,6- bis(dibutylamino)-s-triazine; the oligomeric compound which is the condensation product of 4,4'-hexamethylenebis(amino-l-acyloxy-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-[(l- acyloxy-2,2,6,6-tetramethylpiperidin-4-yl)butylamino]-s-triazine end-capped with 2-chloro-4,6- bis(dibutylamino)-s-triazine; and a product obtained by reacting a product, obtained by reacting l,2-bis(3-aminopropylamino)ethane with cyanuric chloride and (2,2,6,6-tetramethylpiperidin-4- yl)butylamine. Also included are the sterically hindered N — H, N-methyl, N-methoxy, N- propoxy, N-octyloxy, N-cyclohexyloxy, N-acyloxy, and N-(2 -hydroxy -2-methylpropoxy) analogues of any of the above mentioned compounds. For example, replacing an N — H hindered amine with an N-methyl hindered amine would be employing the N-methyl analogue in place of the N-H.

[0184] Illustrative red-shifted hydroxyphenyltriazine UV absorbers include, but are not limited to, 2,4-bis(2-hydroxy-4-n-butyloxyphenyl)-6-(2,4-di-n-butyloxyphenyl)-s-triazine; 2,4, 6-tri s(2 -hydroxy -4-isooctyloxycarbonylisopropylideneoxyphenyl)-s-triazine; 2,4,6-tris[2- hydroxy-4-(3-sec-butyloxy-2-hydroxypropyloxy)phenyl]-l,3,5-triazine; 2-(2,4dihydroxyphenyl)-4.6-bis(2-hydroxy-4(l-methoxycarbonylpentoxy)phenyl)-l,3,5-triazine; 2,4,6-tris(2-hydroxy-4- (l-methoxycarbonyl-pentoxy)phenyl)-l,3,5triazine; 2-(2,4-di(methoxycarbonylpentoxy)phenyl)-4.6-bis(2-hydroxy-4-(l-methoxycarbonylpentoxy)phenyl)-l,3,5-triazine; 2-(2,4- dihydroxyphenyl)-4, 6-bis-(2-hydroxy-4-(l -hydroxy carbonylpentoxy )phenyl)-l, 3, 5-tri azine;2.4.6-tris(2-hydroxy-4-(l-hydroxycarbonyl-pentoxy)phenyl)-l,3,5-triazine; 2-(2,4- di (hydroxycarbonylpentoxy )phenyl)-4,6-bis(2 -hydroxy -4-(l -hydroxy carbonylpentoxy )phenyl)- 1,3, 5 -tri azine; 2,4-bis[2-hydroxy-4-(3-n-butoxy-2-hydroxypropoxy)phenyl]-6-[2-methoxy-4-(3- n-butoxy-2-hydroxypropoxy)phenyl]-l,3,5-triazine; 2,4-bis[2-hydroxy-4-(3-n-butoxy-2- hydroxypropoxy)phenyl]-6-[2,4-di-(3-n-butoxy-2-hydroxypropoxy)phenyl]-l,3,5-triazine; 2,4- bis[2-hydroxy-4-(l-ethoxycarbonylethoxy)phenyl]-6-[2,4-di-(l-ethoxycarbonylethoxy)phenyl]- 1,3, 5 -tri azine; 2,4,6-tris(2'-hydroxy-4'-isopropyloxyphenyl)-l,3,5-triazine; 2,4, 6-tris(2 '-hydroxy - 4'-n-hexyloxyphenyl)-l,3,5-triazine; 2,4-bis(2'-hydroxy-4'-isopropyloxyphenyl)-6-(2'-methoxy- 4'-isopropyloxyphenyl)-l,3,5-triazine; 2,4-bis(2'-hydroxy-4'-isopropyloxyphenyl)-6-(2'-ethoxy- 4'-isopropyloxypheny l)-l,3,5-triazine; 2,4-bis(2'-hydroxy-4'-isopropyloxyphenyl)-6-(2',4'- diisopropyloxyphenyl)-l,3,5-triazine; 2,4-bis(2'-hydroxy-4'-n-hexyloxyphenyl)-6-(2',4'-di-(n- hexyloxy)phenyl)-l-3,5-triazine, and mixtures of any two or more thereof.

[0185] The aqueous coating composition may be suitable for coating automotive components and substrates and may be suitable for original finish and refinish automotive applications.240878W001Further, the aqueous coating composition may be characterized as a monocoat coating composition, and may be structured to be applied to the substrate as a single, uniformly- pigmented layer. Alternatively, the aqueous coating composition may be characterized as a basecoat / cl earcoat coating composition, and may be structured to be applied to the substrate as two distinct layers, i.e., a lower, highly pigmented layer or basecoat, and an upper layer or clearcoat having little or no pigmentation. Basecoat / clearcoat coating compositions may impart a comparatively high level of gloss and depth of color.Forming the Aqueous Coating System

[0186] The method of forming the aqueous coating system includes combining, reacting, and blending. The method further includes applying a film formed from the aqueous coating composition to the substrate. Applying may include, for example, spray coating, dip coating, roll coating, curtain coating, knife coating, spreading, pouring, dipping, impregnating, trickling, rolling, and combinations thereof. For automotive applications in which the substrate is, for example, a body panel, applying may include spray coating the aqueous coating composition onto the substrate. Nonlimiting example of suitable spray coating may include compressed-air spraying, airless spraying, high-speed rotation, electrostatic spray application, hot-air spraying, and combinations thereof. During applying, the substrate may be at rest, and application equipment configured for applying the aqueous coating composition to the substrate may be moved. Alternatively the substrate, e.g., a coil, may be moved, and the application equipment may be at rest relative to the substrate.

[0187] Nonlimiting examples of suitable substrates include metal substrates such as bare steel, phosphated steel, galvanized steel, or aluminum; and non-metallic substrates, such as plastics and composites. The substrate may also include a layer formed from another coating composition, such as a layer formed from an electrodeposited primer coating composition, primer surfacer composition, and / or basecoat coating composition, whether cured or uncured.

[0188] For example, the substrate may be pretreated to include a layer formed from an electrodeposition (electrocoat) primer coating composition. The electrodeposition primer coating composition may be any electrodeposition primer coating composition useful for automotive vehicle coating operations. The electrodeposition primer coating composition may have a dry film thickness of from about 10 pm to about 35 pm and may be curable by baking at a temperature of from about 135 °C to about 190 °C for a duration of from about 15 minutes to about 60 minutes. Nonlimiting examples of electrodeposition primer coating compositions are240878W001 commercially available under the trade name CathoGuard® from BASF Corporation of Florham Park, New Jersey.

[0189] Such electrodeposition primer coating compositions may include an aqueous dispersion or emulsion including a principal film-forming epoxy resin having ionic stabilization, e.g., salted amine groups, in water or a mixture of water and an organic cosolvent. The principal film-forming resin may be emulsified with a crosslinking agent that is reactive with functional groups of the principal film-forming resin under certain conditions, such as when heated, so as to cure a layer formed from the electrodeposition primer coating composition. Suitable examples of crosslinking agents, include, without limitation, blocked polyisocyanates. The electrodeposition primer coating compositions may further include one or more pigments, catalysts, plasticizers, coalescing aids, antifoaming aids, flow control agents, wetting agents, surfactants, ultraviolet light absorbers, hindered amine light stabilizer compounds, antioxidants, and other additives.

[0190] The method also includes curing the film to form the aqueous coating composition. Curing may include, for example, drying the aqueous coating composition so that at least some of any solvent and / or water is stripped from the film during an evaporation phase. Drying may include heating the film at a temperature of from about room temperature to about 80° C. Subsequently, the film may be baked, for example, under conditions employed for automotive original equipment manufacturer finishing, such as at temperatures from about 30 °C to about 200 °C, or from about 70 °C to about 180 °C, or from about 90 °C to about 160 °C, for a duration of from about 20 minutes to about 10 hours, e.g., about 20 minutes to about 30 minutes for comparatively lower baking temperatures and from about 1 hour to about 10 hours for comparatively higher baking temperatures. In one example, the film may be cured at a temperature of from about 90 °C to about 160 °C for a duration of about 1 hour.

[0191] In addition, curing may not occur immediately after applying. Rather, curing may include allowing the film to rest or “flash”. That is, the film may be cured after a certain rest time or “flash” period. The rest time allows the aqueous coating composition to, for example, level and devolatilize such that any volatile constituents such as solvents may evaporate. Such a rest time may be assisted or shortened by the exposing the film to elevated temperatures or reduced humidity. Curing of the aqueous coating composition may include heating the film in a forced-air oven or irradiating the film with infrared lamps.

[0192] The resulting cured film may have a thickness of from about 5 pm to about 75 pm, e.g., about 30 pm to about 65 pm, depending, for example, upon a desired color or continuity of240878W001 the cured film. Further, the cured film formed from the aqueous coating composition 14 may exhibit a metallic and / or pearlescent appearance.

[0193] Therefore, the aqueous coating system may include the substrate and the cured film formed from the aqueous coating composition and disposed on the substrate. Therefore, the method may also include, after curing, exposing the cured film to light without photo-degrading the cured film. That is, the first layer and the second layer of the passivated pigment slurry may provide the cured film formed from the aqueous coating composition with excellent photodegradation protection upon exposure to wavelengths from ultraviolet light, visible light, and / or infrared radiation.

[0194] As such, the photonic particle slurry or dispersion may be used in coating compositions for original finish and refinish automotive coating compositions, such as multicoat coating systems comprising at least one basecoat and at least one clearcoat disposed on the at least, in which the basecoat has been produced using the photonic particle slurry.

[0195] Nonlimiting examples of suitable clearcoat coating compositions may include poly (meth)acryl ate polymers, polyvinyl polymers, and polyurethanes. For example, the clearcoat composition may include a carbamate- and / or hydroxyl-functional poly(meth)acrylate polymer. For embodiments including a polymer having hydroxyl and / or carbamate functional groups, the crosslinking agent may be an aminoplast resin.Basecoat Embodiments

[0196] In certain embodiments, the coating compositions may include one or more organic solvents. Nonlimiting examples of suitable solvents include aromatic hydrocarbons, ketones, esters, glycol ethers, and esters of glycol ethers. Specific examples include, without limitation, methyl ethyl ketone, methyl isobutyl ketone, m-amyl acetate, ethylene glycol butyl ether and ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether and propylene glycol monomethyl ether acetate, xylene, ethanol, propanol, isopropanol, n-butanol, isobutanol, tert-butanol, N-methyl pyrrolidone, N-ethyl pyrrolidone, Aromatic 100, Aromatic 150, naphtha, mineral spirits, butyl glycol, and so on.

[0197] The coating composition may optionally include further rheology control agents, including high molecular weight mixed cellulose esters, such as CAB-381-0.1, CAB-381-20. CAB-531-1, CAB-551-0.01, and CAB-171-15S (available from Eastman Chemical Company, Kingsport, Tennessee), which may be included in amounts of up to about 5 wt.%, or from about 0.1 to about 5 wt.%, or from about 1.5 to about 4.5 wt.%, based on total binder weight. Further examples include microgel rheology control agents such as crosslinked acrylic polymeric240878W001 microparticles, which may be included in amounts of up to about 5 wt.% of total binder weight; wax rheology control agents such as polyethylene waxes including acrylic acid-modified polyethylene wax (e.g., Honeywell A-C® Performance Additives), poly(ethylene-vinyl acetate) copolymers, and oxidized polyethylenes, which may be included in amounts of up to about 2 wt.% on total binder weight; and fumed silicas, which may be included in amounts of up to about 10 wt.% on total binder weight or from about 3 to about 12 wt.% on total binder weight.

[0198] Additional agents, for example hindered amine light stabilizers, ultraviolet light absorbers, anti-oxidants, surfactants, stabilizers, wetting agents, adhesion promoters, etc. may be incorporated into the coating composition. Such additives are well-known and may be included in amounts typically used for coating compositions.

[0199] Nonlimiting examples of special effect pigments that may be utilized in basecoat and monocoat coating compositions include metallic, pearlescent, and color-variable effect flake pigments. Metallic (including pealescent, and color-variable) colors are produced using one or more special flake pigments. Metallic colors are generally defined as colors having gonioapparent effects. For example, the American Society of Testing Methods (ASTM) document F284 defines metallic as “pertaining to the appearance of a gonioapparent material containing metal flake.” Metallic basecoat colors may be produced using metallic flake pigments like aluminum flake pigments, coated aluminum flake pigments, copper flake pigments, zinc flake pigments, stainless steel flake pigments, and bronze flake pigments and / or using pearlescent flake pigments including treated micas like titanium dioxide-coated mica pigments and iron oxide-coated mica pigments to give the coatings a different appearance (degree of reflectance or color) when viewed at different angles. Metal flakes may be cornflake type, lenticular, or circulation-resistant; micas may be natural, synthetic, or aluminum-oxide type. Flake pigments do not agglomerate and are not ground under high shear because high shear would break or bend the flakes or their crystalline morphology, diminishing or destroying the gonioapparent effects. The flake pigments are satisfactorily dispersed in a binder component by stirring under low shear. The flake pigment or pigments may be included in the high solids coating composition in an amount of about 0.01 wt.% to about 0.3 wt.% or about 0.1 wt.% to about 0.2 wt.%, in each case based on total binder weight.

[0200] Nonlimiting examples of commercial flake pigments include PALIOCROME® pigments, available from BASF Corporation.

[0201] Nonlimiting examples of other suitable pigments and fillers that may be utilized in basecoat and monocoat coating compositions include inorganic pigments such as titanium dioxide, barium sulfate, carbon black, ocher, sienna, umber, hematite, limonite, red iron oxide,240878W001 transparent red iron oxide, black iron oxide, brown iron oxide, chromium oxide green, strontium chromate, zinc phosphate, silicas such as fumed silica, calcium carbonate, talc, barytes, ferric ammonium ferrocyanide (Prussian blue), and ultramarine, and organic pigments such as metallized and non-metallized azo reds, quinacridone reds and violets, perylene reds, copper phthalocyanine blues and greens, carbazole violet, monoarylide and diarylide yellows, benzimidazolone yellows, tolyl orange, naphthol orange, and so on. The pigment or pigments are preferably dispersed in a resin or polymer or with a pigment dispersant, such as binder resins. In general, the pigment and dispersing resin, polymer, or dispersant are brought into contact under a shear high enough to break the pigment agglomerates down to the primary pigment particles and to wet the surface of the pigment particles with the dispersing resin, polymer, or dispersant. The breaking of the agglomerates and wetting of the primary pigment particles are important for pigment stability and color development. Pigments and fillers may be utilized in amounts typically of up to about 40% by weight, based on total weight of the coating composition.

[0202] In certain embodiments, the disclosed basecoats may have about 40 wt.% to about 55 wt.%, nonvolatile content, and typically may have about 45 wt.% to about 50 wt.% nonvolatile content, as determined by ASTM Test Method D2369, in which the test sample is heated at 110 °C. (230 °F) for 60 minutes.

[0203] In certain embodiments, a substrate may be coated by applying a primer layer, optionally curing the primer layer; then applying a basecoat layer and a clearcoat layer, typically wet-on-wet, and curing the applied layers and optionally curing the primer layer along with the basecoat and clearcoat layers if the primer layer is not already cured, or then applying a monocoat layer and curing the monocoat layer, again optionally curing the primer layer along with the basecoat and clearcoat layers if the primer layer is not already cured. The cure temperature and time may vary depending upon the particular binder components selected, but typical industrial and automotive thermoset compositions prepared as we have described may be cured at a temperature of from about 105° C. to about 175° C., and the length of cure is usually about 15 minutes to about 60 minutes.

[0204] The coating composition can be coated on a substrate by spray coating. Electrostatic spraying is a preferred method. The coating composition can be applied in one or more passes to provide a film thickness after cure of a desired thickness, typically from about 10 to about 40 microns for primer and basecoat layers and from about 20 to about 100 microns for clearcoat and monocoat layers.240878W001

[0205] The coating composition can be applied onto many different types of substrates, including metal substrates such as bare steel, phosphated steel, galvanized steel, or aluminum; and non-metallic substrates, such as plastics and composites. The substrate may also be any of these materials having upon it already a layer of another coating, such as a layer of an electrodeposited primer, primer surfacer, and / or basecoat, cured or uncured.

[0206] The substrate may be first primed with an electrodeposition (electrocoat) primer. The electrodeposition composition can be any electrodeposition composition used in automotive vehicle coating operations. Non-limiting examples of electrocoat compositions include the CATHOGUARD® electrocoating compositions sold by BASF Corporation, such as CATHOGUARD® 500. Electrodeposition coating baths usually comprise an aqueous dispersion or emulsion including a principal film-forming epoxy resin having ionic stabilization (e.g., salted amine groups) in water or a mixture of water and organic cosolvent. Emulsified with the principal film-forming resin is a crosslinking agent that can react with functional groups on the principal resin under appropriate conditions, such as with the application of heat, and so cure the coating. Suitable examples of crosslinking agents, include, without limitation, blocked polyisocyanates. The electrodeposition coating compositions usually include one or more pigments, catalysts, plasticizers, coalescing aids, antifoaming aids, flow control agents, wetting agents, surfactants, UV absorbers, HALS compounds, antioxidants, and other additives.

[0207] The electrodeposition coating composition is preferably applied to a dry film thickness of 10 to 35 micron. After application, the coated vehicle body is removed from the bath and rinsed with deionized water. The coating may be cured under appropriate conditions, for example by baking at from about 275° F. to about 375° F. (about 135° C. to about 190° C.) for between about 15 and about 60 minutes.ILLUSTRATIVE EXAMPLES

[0208] The following examples are set forth to assist in understanding the disclosed embodiments and should not be construed as specifically limiting the embodiments described and claimed herein. Such variations of the embodiments, including the substitution of all equivalents now known or later developed, which would be within the purview of those skilled in the art, and changes in formulation or minor changes in experimental design, are to be considered to fall within the scope of the embodiments incorporated herein.

[0209] Coatings of the present disclosure may be formed to produce, for example, the exemplary system shown in FIG. 4, where a photosensitive color layer comprises a clear coat240878W001 layer for UV absorption deposited thereon according to certain embodiments of the present disclosure.Example 1

[0210] A base composition for use in preparing coating samples is summarized in Table 1.A series of coating samples were prepared according to Table 2 using the base composition, including a control sample without any UV light absorb ers / HALS compounds or porous metal oxide particles, and Samples 1-8 that included various combinations of UV light absorbers / HALS compounds and / or porous metal oxide particles.

[0211] Slides were prepared having coatings of the control sample and Samples 1-8 formed thereon were prepared using clear coat drawn-down (targeting 75 pM wet film thickness) on quartz slides (FSUV-S-002 from AdValue Technology). UV-vis spectra were measured for each dried sample from 190-1100 nm on a Perkin Elmer Lambda 365 spectrometer.Table 1 : Base compositionTable 2: Sample formulations (all units in wt % based on total weight of the final composition)240878W001

[0212] Table 3 shows the absorbances for each sample at 305nm and 355nm, while FIGS. 6A and 6B show their corresponding UV-vis spectra. This data shows the UV-vis absorbance results of various combinations UV light absorbers (Tinuvin 477 DW), HALS (Tinuvin 249 DW), and porous metal oxide particles including porous silica microspheres, silica closed-cell microspheres, and hybrid microspheres. The results show that addition of microspheres enhanced Tinuvin 477 UV absorption in the order of: silica closed-cell microspheres > porous microspheres > hybrid microspheres. Addition of microspheres to formulations containing HALS showed no UV absorbance effect.Table 3: Absorbances at 305nm and 355nm

[0213] It was observed that the starting baseline varied depending on the slide being analyzed, which was likely due to the visual difference in the coatings. It was noted that the control, Sample 1 and Sample 5 were visually similar, while other similar pairs were Samples 2 and 6, Samples 3 and 7, and Samples 4 and 8. FIG. 7 shows a visual comparison of the coated Samples.Example 2

[0214] Porous titania particles were tested to evaluate their ability to impart a UV attenuation boost to coatings with UV light absorbers, using Joncryl® 2981 (available form BASF) as the base coating formulation. Drawdowns on glass at 2 mm wet thickness were prepared containing240878W0011 wt% of a Tinuvin® light absorber (four different types were used) and 1 wt% TiCh porous particles. FIG. 8 shows attenuation plots as functions of light absorber concentration (UV absorber or light stabilizer). Each plot shows the increase in attenuation of UV light in a sample containing both TiCh porous microspheres and a UV absorber / light stabilizer (Tinuvin® 400- DW in top left, Tinuvin® 9945-DW in top right, Tinuvin® 477-DW in bottom left, and Tinuvin® 5333-DW in bottom right), as denoted by the black outline circle. A standard curve of the same UV absorber / light stabilizer at the same film thickness (dots connected by dashed curve) is shown for comparison. The black outline circle corresponds to UV attenuation due to the TiC>2 porous microspheres for which background UV attenuation of the porous microspheres has been subtracted at the same wavelength. As a result, any difference between the black outline circle and the point along the curve is due to the boosting effect of the porous microspheres.

[0215] FIG. 9 shows attenuation curves corresponding to those shown in FIG. 8, with the difference being that the improvement resulting from the presence of the TiCh porous microspheres does not have background UV attenuation subtracted. Thus, the black outline circles of FIG. 9 correspond to an absolute improvement in UV attention resulting from the presence of porous metal oxide particles. The results indicate increased absorbance due to the presence of the porous TiCh particles, and the synergistic effect of porous TiCh particles with Tinuvin® absorbers. For example, similar UV protection can be achieved using 1 / 3 of the Tinuvin® 400-DW when used in combination with 1 wt% porous TiCh particles.

[0216] In the foregoing description, numerous specific details are set forth, such as specific materials, dimensions, processes parameters, etc., to provide a thorough understanding of the embodiments of the present disclosure. The particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments. The words “example” or “exemplary” are used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as “example” or “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, use of the words “example” or “exemplary” is intended to present concepts in a concrete fashion.

[0217] As used in this application, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or”. That is, unless specified otherwise, or clear from context, “X includes A or B” is intended to mean any of the natural inclusive permutations. That is, if X includes A; X includes B; or X includes both A and B, then “X includes A or B” is satisfied under any of the foregoing instances. In addition, the articles “a” and “an” as used in this application and the240878W001 appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from context to be directed to a singular form.

[0218] Reference throughout this specification to “an embodiment”, “certain embodiments”, or “one embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrase “an embodiment”, “certain embodiments”, or “one embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, and such references mean “at least one”.

[0219] It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reading and understanding the above description. The scope of the disclosure should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

240878W001What is claimed is:

1. A coating composition comprising: a solvent; a binder; a UVA absorbing compound; and photonic particles selected from porous metal oxide particles, hybrid metal oxide particles, closed-cell metal oxide particles, or a combination thereof, wherein a coating formed from the coating composition exhibits a UV attenuation boost of at least about 50%.

2. The coating composition of claim 1, wherein the UV attenuation boost is at least about 60%, at least about 70%, at least about 80%, at least about 90%, at least about 100%, at least about 110%, at least about 120%, at least about 130%, at least about 140%, at least about 150%, at least about 160%, at least about 170%, at least about 180%, at least about 190%, or at least about 200%.

3. The coating composition of claim 1, wherein the photonic particles are present in the coating from about 0.5 wt% to about 2 wt% based on total dry weight of the coating.

4. The coating composition of claim 1, wherein the UVA absorbing compound is present in the coating at less than about 3 wt%, less than about 2 wt%, less than about 1 wt%, or less than about 0.5 wt% based on total dry weight of the coating.

5. The coating composition of claim 1, wherein the UVA absorbing compound comprises a hindered amine light stabilizer compound.

6. The coating composition of claim 1, further comprising a component selected from: a dispersant; a surfactant; a defoaming agent; a co-dispersant; an acrylic binder; a rheology modifier; a coalescing agent; or a combination thereof.

7. The coating composition of claim 1, comprising the porous metal oxide particles, wherein the porous metal oxide particles have: an average diameter of from about 0.5 pm to about 100 pm;240878W001 an average porosity of from about 0.45 to about 0.8; and at least one population of pores each having an average pore diameter of from about 100 nm to about 800 nm.

8. The coating composition of claim 7, wherein the porous metal oxide particles have: an average diameter of from about 1 pm to about 75 pm; an average porosity of from about 0.45 to about 0.8; and at least one population of pores each having an average pore diameter of from about 100 nm to about 800 nm.

9. The coating composition of claim 7, wherein the metal oxide of the porous metal oxide particles is selected from the group consisting of silica, titania, alumina, zirconia, ceria, iron oxide, zinc oxide, indium oxide, tin oxide, chromium oxide, and combinations thereof.

10. The coating composition of claim 7, wherein the pores of the porous metal oxide particles form an ordered array or a disordered array.

11. The coating composition of claim 1, comprising the hybrid metal oxide particles, wherein the hybrid metal oxide particles comprise a continuous matrix of a first metal oxide having embedded therein an array of metal oxide particles, the metal oxide particles comprising a second metal oxide, wherein the hybrid metal oxide particles are substantially non-porous.

12. The coating composition of claim 11, wherein the hybrid metal oxide particles have: an average diameter of from about 0.5 pm to about 50 pm; and an average diameter of the metal oxide particles of from about 100 nm to about 600 nm.

13. The coating composition of claim 11, wherein the first metal oxide and the second metal oxide independently comprise a metal oxide selected from silica, titania, alumina, zirconia, ceria, iron oxides, zinc oxide, indium oxide, tin oxide, chromium oxide, and combinations thereof.

14. The coating composition of claim 11, wherein the array of the metal oxide particles is an ordered array or a disordered array.240878W00115. The coating composition of claim 1, comprising the closed-cell metal oxide particles, wherein each closed-cell metal oxide particle comprises a metal oxide matrix defining an array of closed-cells, wherein each closed-cell encapsulates a media-inaccessible void volume, wherein the outer surface of the closed-cell metal oxide particle is defined by the array of closed- cells.

16. The coating composition of claim 15, wherein the closed-cell metal oxide particles have: an average diameter of from about 1 pm to about 75 pm; an average void volume diameter of from about 50 nm to about 800 nm; and an average porosity of from about 0.45 to about 0.65.

17. The coating composition of claim 15, wherein the closed-cell metal oxide particles have: an average diameter of from about 0.5 pm to about 50 pm; an average void volume diameter of from about 100 nm to about 800 nm; and an average porosity of from about 0.45 to about 0.65.

18. The coating composition of claim 15, wherein the metal oxide matrix comprises a metal oxide selected from silica, titania, alumina, zirconia, ceria, iron oxides, zinc oxide, indium oxide, tin oxide, chromium oxide, and combinations thereof.

19. The coating composition of claim 15, wherein the array of the closed-cells is an ordered array or a disordered array.

20. A coating derived from the composition of any preceding claim.

21. A coating comprising: a photosensitive colorant layer; and a clear coat layer disposed above the colorant layer to provide UV protection thereto, the clear coat laying being formed from the coating composition of any one of claims 1-20.

22. The coating of claim 21, further comprising one or more additional layers (i) between a ground layer and the colorant layer, (ii) between the colorant layer and the clear coat layer, (iii) over the clear coat layer, or a combination thereof.240878W00123. An article of manufacture comprising a substrate and a coating of either claim 21 or claim 22.

24. The article of manufacture of claim 23, wherein the substrate is an automotive part.

25. The article of manufacture of claim 24, wherein the automotive part is an external panel or an interior part.

26. A method of preparing a coating composition comprising mixing a solvent, a binder, and a photonic particles to obtain the coating composition of any of claims 1-19.

27. A method of coating a substrate comprising layering the coating composition of any of claims 1-19 onto a substrate.

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