Porous metal oxide microspheres

Abstract

To provide porous microspheres exhibiting saturated colors and suitable as colorants for various end uses.SOLUTION: A method for producing porous metal oxide microspheres including a metal oxide comprises: producing a dispersion liquid of polymer nanoparticles and a metal oxide; producing liquid droplets of the dispersion; drying the liquid droplets to obtain polymer template microspheres containing polymer nanospheres; and removing the polymer nanospheres from the template microspheres to obtain the porous metal oxide microspheres.SELECTED DRAWING: None

Description

[Technical Field]

[0001] Porous metal oxide microspheres, methods for their preparation, and uses are disclosed. The microspheres are suitable for use, for example, as structural colorants.

[0002] Background of the Invention Traditional pigments and dyes rely on chemical structure to produce color through light absorption and reflection. Structural colorants rely on physical structure rather than chemical structure to produce color through light interference effects. Structural colorants are found in nature, for example, in bird feathers, butterfly wings, and certain gemstones. Structural colorants are materials that contain microscopic structural surfaces small enough to interfere with visible light and produce color. Such materials may be based on photonic materials, such as, but not limited to, opals, inverse opals, photonic microspheres, photonic spheres, or composite photonic crystals. The term "photonic material" refers to materials that have some degree of periodic variation in their structure.

[0003] Structural colorants can exhibit high stability. Therefore, structural colorants that exhibit distinct visible colors observable to the naked eye when present in bulk are desirable. Such structural colorants can be incorporated into consumer products in place of less stable and / or less environmentally friendly pigments or dyes.

[0004] Certain porous metal oxide microspheres have been found to exhibit high quality color in bulk, providing visible color in bulk.

[0005] Summary of the Invention Thus, a method for producing porous metal oxide microspheres comprising a metal oxide is disclosed, the method comprising: producing a dispersion of polymer nanoparticles and a metal oxide; producing droplets of the dispersion; drying the droplets to obtain polymer template microspheres comprising the polymer nanospheres and the metal oxide; and removing the polymer nanospheres from the template microspheres to obtain porous metal oxide microspheres.

[0006] Also disclosed are porous microspheres comprising a metal oxide, the microspheres having an average diameter of about 0.5 μm to about 100 μm, an average porosity of about 0.10 to about 0.90 or about 0.10 to about 0.80, and an average pore size of about 50 nm to about 999 nm.

[0007] Also disclosed are porous microspheres comprising a metal oxide, wherein a bulk sample of the porous microspheres exhibits a color observable by the human eye.

[0008] Compositions comprising a substrate and the porous microspheres are also disclosed, for example, the compositions are aqueous formulations, oil-based formulations, coating formulations, foods, inks, plastics, cosmetic formulations, or materials for medical or security applications.

[0009] The disclosure described herein is illustrated by way of example, and not by way of limitation, in the accompanying figures. For simplicity and clarity of illustration, the features illustrated in the figures have not necessarily been drawn to scale. For example, the dimensions of some features may be exaggerated relative to other features for clarity. Furthermore, where appropriate, reference numerals have been repeated among the figures to refer to corresponding or similar elements. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is an overview of the fabrication of porous microspheres according to one embodiment of the present invention. [Figure 2]1 is a scanning electron microscope (SEM) image of a polymer-templated microsphere of one embodiment of the present invention. [Figure 3] 1 is an SEM image of porous silica microspheres according to one embodiment of the present invention. [Figure 4] FIG. 1 is a representative diagram of a spray drying process according to some embodiments of the present invention.

[0011] Detailed Description of the Invention The metal oxide microspheres, or photonic balls, can be fabricated using a polymeric sacrificial template. In one embodiment, an aqueous colloidal dispersion containing polymer particles and a metal oxide is prepared, and the polymer particles are generally nanoscale. This aqueous colloidal dispersion is mixed with an oil continuous phase, for example, in a microfluidic device, to produce a water-in-oil emulsion. The emulsion droplets are prepared, collected, and dried to produce microspheres containing polymer nanoparticles and a metal oxide. The polymer nanoparticles (nanospheres) are then removed, for example, by calcination, to yield spherical, micron-scale metal oxide particles (microspheres) with high porosity and nanoscale pores. As a result of the spherical and monodisperse nature of the polymer particles, the microspheres can have uniform pore sizes.

[0012] Figure 1 shows an overview of the fabrication of the present porous microspheres. Emulsion droplets containing polymer nanospheres and metal oxide are dried to remove the solvent, resulting in a collection of microspheres containing polymer nanospheres with the metal oxide in the interstitial spaces between them (templated microspheres or "forward architecture"). The polymer nanospheres define the interstitial spaces. Calcination results in the removal of the polymer, resulting in the present metal oxide microspheres with increased porosity or void volume (inverse architecture).

[0013] The porous metal oxide microspheres are advantageously sintered, resulting in a continuous solid structure that is thermally and mechanically stable.

[0014] In some embodiments, droplet formation and collection occur within a microfluidic device. A microfluidic device is, for example, a narrow channel device connected to a collection reservoir, with a micron-scale droplet junction adapted to produce droplets of uniform size. The microfluidic device contains a droplet junction with a channel width of, for example, about 10 μm to about 100 μm. The device may be made of, for example, polydimethylsiloxane (PDMS) and may be fabricated by, for example, soft lithography. When a water-dispersed phase and an oil-continuous phase are fed into the device at a specific rate, they are mixed within the device to produce an emulsion within the device, resulting in emulsion droplets. Alternatively, an oil-in-water emulsion may be used.

[0015] In some embodiments, a vibrating nozzle technique may be used. In these techniques, a dispersion is prepared, droplets are formed, and the droplets fall into a bath of a continuous phase. The droplets are then dried before the polymer is removed. Vibrating nozzle devices are available from Büchi and include, for example, a syringe pump and a pulsating unit. The vibrating nozzle device may also include a pressure control valve.

[0016] The polymeric nanoparticles have, for example, an average diameter of about 50 nm to about 999 nm and are monodisperse.

[0017] Suitable template polymers include thermoplastic polymers, for example, template polymers selected from the group consisting of poly(meth)acrylic acid, poly(meth)acrylate, polystyrene, polyacrylamide, polyvinyl alcohol, polyvinyl acetate, polyester, polyurethane, polyethylene, polypropylene, polylactic acid, polyacrylonitrile, polyvinyl ether, derivatives thereof, salts thereof, copolymers thereof, and combinations thereof. For example, the polymer is selected from the group consisting of polymethyl methacrylate, polyethyl methacrylate, poly(n-butyl methacrylate), polystyrene, poly(chlorostyrene), poly(alpha-methylstyrene), poly(N-methylolacrylamide), styrene / methyl methacrylate copolymer, polyalkylated acrylate, polyhydroxyl acrylate, polyaminoacrylate, 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, derivatives thereof, salts thereof, and combinations thereof.

[0018] In certain embodiments, polymer templates include various polystyrenes, such as polystyrene and polystyrene copolymers, including copolymers with water-soluble monomers, such as polystyrene / acrylic acid, polystyrene / poly(ethylene glycol) methacrylate, and polystyrene / styrene sulfonate.

[0019] The metal oxides include transition metal, metalloid, and rare earth oxides, such as silica, titania, alumina, zirconia, ceria, iron oxide, zinc oxide, indium oxide, tin oxide, chromium oxide, mixed metal oxides, combinations thereof, and the like.

[0020] The wt / wt (weight / weight) ratio of polymer nanoparticles to metal oxide is, for example, from about 0.1 / 1 to about 10.0 / 1, or from about 0.5 / 1 to about 10.0 / 1.

[0021] The oil continuous phase includes, for example, organic solvents, silicone oils, or fluorinated oils. In the present invention, "oil" refers to an organic phase that is not miscible with water. Organic solvents include hydrocarbons such as heptane, hexane, toluene, xylene, etc., and alkanols such as methanol, ethanol, propanol, etc.

[0022] The emulsion droplets are collected, dried, and the polymer removed. Drying can be carried out, for example, by microwave irradiation, in a thermal oven, under vacuum, in the presence of a desiccant, or a combination thereof.

[0023] Polymer removal can be accomplished, for example, by calcination, pyrolysis, or with a solvent (solvent removal). Calcination, in some embodiments, is carried out at a temperature 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. Calcination can be carried out for a suitable time, for example, from about 0.1 hours to about 12 hours, or from about 1 hour to about 8.0 hours. In other embodiments, calcination can be for at least about 0.1 hours, at least about 1 hour, at least about 5 hours, or at least about 10 hours.

[0024] Alternatively, a dispersion containing polymer nanoparticles and metal oxides can be made with an oil dispersed phase and a water continuous phase, so that an oil-in-water emulsion is formed. The oil droplets can be collected and dried in the same way as water droplets.

[0025] Alternatively, a dispersion of polymer nanoparticles and a metal oxide is prepared and spray-dried to produce polymer-templated microspheres without forming a liquid-in-liquid emulsion. In a specific embodiment of the spray-drying technique, a solution or dispersion is supplied (e.g., pumped) to a spray nozzle connected to a compressed gas inlet. The feed is pumped through the spray nozzle to form droplets. These droplets are surrounded by preheated gas in an evaporation chamber, resulting in evaporation of the solvent and production of solid particles. The dried particles are carried through a cyclone by the drying gas and deposited in a collection chamber. The gas may include nitrogen and / or air. In one embodiment of this spray-drying process, the liquid feed contains an aqueous or oil phase, polymer particles, and a metal oxide. In one embodiment of this spray-drying process, the liquid feed contains an aqueous or oil phase, polymer particles, and optionally a metal oxide. Polymer-templated microspheres are obtained containing polymer nanospheres, with the metal oxide contained in the interstitial spaces between the polymer nanospheres. The polymer nanospheres define the interstitial spaces. Spray drying techniques include inkjet spray drying methods and apparatus.

[0026] In this spray drying technique, air can be considered the continuous phase as opposed to the dispersed liquid phase (liquid-in-gas emulsion). In certain embodiments, spray drying involves an inlet temperature 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 about 180°C, about 190°C, about 200°C, about 210°C, about 215°C, or about 220°C. In some embodiments, a feed rate (feed flow rate) 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 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 used. Spray drying techniques are disclosed, for example, in U.S. Patent Application Publication No. 2016 / 0170091.

[0027] FIG. 4 is a representative diagram of a spray drying process according to some embodiments of the present invention.

[0028] Microspheres are spherical or sphere-like and are micron-scale, for example, having an average diameter of about 0.5 microns (μm) to about 100 μm. The polymer nanoparticles used as templates are also spherical, nanoscale, and monodisperse, for example, having an average diameter of about 50 nm to about 999 nm. The metal oxides used may also be in the form of particles, which may be nanoscale.

[0029] The metal oxides of the dispersion may be provided as metal oxides or may be prepared from metal oxide precursors, for example by sol-gel techniques.

[0030] Drying the polymer / metal oxide droplets and then removing the polymer yields microspheres with uniform voids (pores). Generally, each droplet yields one microsphere in this process. The pore size depends on the size of the polymer particle. After polymer removal, some "shrinkage" or compaction may occur, resulting in pore sizes somewhat smaller than the original polymer particle size, e.g., about 10% to about 40% smaller than the polymer particle size. The pore size is uniform, as are the shape and size of the polymer particles.

[0031] Pore ​​sizes, in some embodiments, can range from about 50 nm to about 999 nm.

[0032] The average porosity of the present metal oxide microspheres can be relatively high, for example, from about 0.10 or about 0.30 to about 0.80 or about 0.90. The average porosity of a microsphere refers to the total pore volume as a fraction of the total volume of the microsphere. The average porosity is sometimes referred to as the "volume fraction."

[0033] In some embodiments, porous microspheres may have a solid core, in which case they are generally more porous toward the outer surface of the microsphere. In other embodiments, porous microspheres may have a hollow core, in which case the majority of the porosity is toward the interior of the microsphere. In other embodiments, the porosity may be distributed throughout the volume of the microsphere. In other embodiments, the porosity may exist as a gradient, with more porosity toward the outer surface of the microsphere and less porosity or no porosity toward the center (solid); or less porosity toward the outer surface and more porosity or completely porous toward the center (hollow).

[0034] For any porous microsphere, the average microsphere diameter is larger than the average pore diameter, for example, the average microsphere diameter is at least about 25 times, at least about 30 times, at least about 35 times, or at least about 40 times larger than the average pore diameter.

[0035] In some embodiments, the ratio of average microsphere size to average pore size is, for example, from about 40 / 1, about 50 / 1, about 60 / 1, about 70 / 1, about 80 / 1, about 90 / 1, about 100 / 1, about 110 / 1, about 120 / 1, about 130 / 1, about 140 / 1, about 150 / 1, about 160 / 1, about 170 / 1, about 180 / 1, or about 190 / 1 to about 200 / 1, about 210 / 1, about 220 / 1, about 230 / 1, about 240 / 1, about 250 / 1, about 260 / 1, about 270 / 1, about 280 / 1, about 290 / 1, about 300 / 1, about 310 / 1, about 320 / 1, about 330 / 1, about 340 / 1, or about 350 / 1.

[0036] Polymer-templated microspheres containing monodisperse polymer nanospheres can yield metal oxide microspheres with pores of generally similar pore size when the polymer is removed.

[0037] Without being bound by theory, it is believed that bulk samples of microspheres exhibit saturated colors with reduced undesirable light scattering when the porosity and / or microsphere size and / or pore size are within a certain range. The color properties of bulk samples are important because colorants are used in bulk, for example, in paints, inks, coatings, cosmetics, or materials for medical or security applications. In some embodiments, white microspheres are desirable, for example, for use as white colorants.

[0038] The porous microspheres may primarily comprise metal oxides, i.e., consist essentially of or consist of metal oxides. Advantageously, bulk samples of the porous microspheres exhibit a color observable by the human eye. Light absorbers may also be present in the microspheres, providing a more saturated observable color. Absorbers include inorganic and organic pigments, such as broadband absorbers, such as carbon black. Absorbers can be added, for example, by physically mixing the microspheres with the absorber or by including the absorber in droplets that are then dried. In the case of carbon black, controlled calcination may be used to produce carbon black in situ from polymer decomposition. While the microspheres may not exhibit an observable color without the addition of a light absorber, the addition of a light absorber will result in an observable color.

[0039] The porous microspheres can be used as colorants for, for example, water-based formulations, oil-based formulations, inks, coating formulations, foods, plastics, cosmetic formulations, or materials for medical or security applications. Coating formulations include, for example, architectural coatings, automotive coatings, varnishes, etc.

[0040] The porous metal oxide microspheres may exhibit angle-dependent or angle-independent color. "Angle-dependent" color means that the observed color depends on the angle of incident light relative to the sample or the angle between the observer and the sample. "Angle-independent" color means that the observed color is substantially independent of either the angle of incident light relative to the sample or the angle between the observer and the sample.

[0041] Angle-dependent color can be achieved, for example, using monodisperse polymer nanospheres. Angle-dependent color can also be achieved by performing a slow drying step of the droplets to obtain polymer-templated microspheres, which allows the polymer nanospheres to order. Angle-independent color can be achieved by performing a fast drying step of the droplets, which does not allow the polymer nanospheres to order.

[0042] For example, the porous microspheres may comprise from about 60.0 wt% (weight percent) to about 99.9 wt% metal oxide and from about 0.1 wt% to about 40.0 wt% of one or more light absorbing agents, based on the total weight of the microsphere.

[0043] Advantageously, the porous microspheres can also be monodisperse.

[0044] In the present invention, particle size is synonymous with particle diameter, and is determined, for example, by scanning electron microscopy (SEM) or transmission electron microscopy (TEM). Average particle size is synonymous with D50, which means that half of the population is above that point and half is below it. Particle size refers to primary particles. Particle size can be measured by laser light scattering techniques using dispersions or dry powders.

[0045] Mercury porosimetry analysis was used to characterize the porosity of the microspheres. In mercury porosimetry, a controlled pressure is applied to a sample immersed in mercury. The externally applied mercury penetrates the voids / pores of the material. The amount of pressure required to penetrate the voids / pores is inversely proportional to the size of the voids / pores. The mercury porosimeter generates volume and pore size distributions from the pressure versus penetration data generated by the instrument using the Washburn equation. For example, porous silica microspheres containing voids / pores with an average size of 165 nm have an average porosity of 0.8.

[0046] The term "bulk sample" refers to a population of microspheres. For example, a bulk sample of microspheres is simply a bulk population of microspheres, e.g., ≧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 microspheres may be substantially free of other components. The term "porous microspheres" may refer to a bulk sample.

[0047] The phrase "exhibiting a color observable by the human eye" means that the color is observable by the average person. This applies to any bulk sample distributed over any surface area, e.g., about 1 cm². 2 , about 2 cm 2 , about 3cm 2 , about 4cm 2 , about 5cm 2 , or about 6 cm 2 Approximately 7 cm from either 2 , about 8cm 2 , about 9cm 2 , about 10cm 2 , about 11cm 2 , about 12cm 2 , about 13cm 2 , about 14cm 2 , or about 15 cm 2It refers to a bulk sample distributed over a surface area up to either the CIE 1931 2° standard observer and / or the CIE 1964 10° standard observer. The background for color observation can be any background, such as a white background, a black background, or a dark background anywhere between white and black.

[0048] The term "of" can mean "comprising," for example, "a dispersion of" can be interpreted as "a dispersion comprising."

[0049] As used herein, the terms "microsphere," "nanosphere," "droplet," and others may refer to, for example, a plurality thereof, a collection thereof, a population thereof, a sample thereof, or a bulk sample thereof.

[0050] The term "micro" or "microscale" means from about 0.5 μm to about 999 μm. The term "nano" or "nanoscale" means from about 1 nm to about 999 nm.

[0051] The terms "sphere" and "particle" may be used interchangeably.

[0052] The term "monodisperse" with respect to a population of microspheres or nanospheres means that the particles have a generally uniform shape and a generally uniform diameter. A monodisperse population of microspheres or nanospheres may have, for example, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% of the particles by number having a diameter within ±7%, ±6%, ±5%, ±4%, ±3%, ±2%, or ±1% of the mean diameter of the population.

[0053] "Substrate" may refer to an aqueous or oily substrate or "vehicle," which may be a minor or major part of the final composition. Substrate may also refer to a solid, semi-solid, gel, liquid, paste, cream, etc.

[0054] Removal of the monodisperse population of polymer nanospheres yields porous metal oxide microspheres with a corresponding population of pores with an average pore size.

[0055] The term "substantially free of other components" means, for example, containing ≦5%, ≦4%, ≦3%, ≦2%, ≦1%, or ≦0.5% (all by weight) of other components.

[0056] As used herein, the articles "a" and "an" refer to one or more than one (e.g., at least one) of the grammatical object. All ranges described herein are inclusive. As used throughout this specification, the term "about" is used to describe and account for small variations. For example, "about" can mean that a numerical value can be varied by ±5%, ±4%, ±3%, ±2%, ±1%, ±0.5%, ±0.4%, ±0.3%, ±0.2%, ±0.1%, or ±0.05%. All numerical values, whether expressly stated or not, are modified by the term "about." Numerical values ​​modified by the term "about" are inclusive of the stated value. For example, "about 5.0" includes 5.0.

[0057] All U.S. patents, U.S. government patent applications, and U.S. published patent applications mentioned herein are hereby incorporated by reference.

[0058] Unless otherwise specified, all parts and percentages are by weight. Weight percent (wt%) is based on the total composition, i.e., dry solid components, without any volatiles, unless otherwise specified.

[0059] A first non-limiting set of embodiments of the present invention relating to methods of making porous metal oxide microspheres include the following.

[0060] In a first embodiment, a method for producing porous metal oxide microspheres comprising a metal oxide is disclosed, the method comprising: producing a dispersion of polymer nanoparticles and a metal oxide; producing droplets of the dispersion; drying the droplets to obtain polymer template microspheres comprising the polymer nanospheres and the metal oxide; and removing the polymer nanospheres from the template microspheres to obtain porous metal oxide microspheres.

[0061] In a second embodiment, the method of the first embodiment includes producing a dispersion of polymeric nanoparticles and a metal oxide, spray drying the dispersion to obtain polymeric template microspheres, and removing the polymeric nanospheres from the template microspheres.

[0062] In a third embodiment, the method of the first embodiment includes producing the droplets using a vibrating nozzle. In a fourth embodiment, the method of any one of the first to third embodiments, wherein the droplets are water droplets. In a fifth embodiment, the method of any one of the first to third embodiments, wherein the droplets are oil droplets.

[0063] In a sixth embodiment, the method of embodiment 1 includes providing a continuous phase and mixing the dispersion with the continuous phase to produce an emulsion containing dispersed droplets. In a seventh embodiment, the method of embodiment 6 includes providing an oil continuous phase and mixing the aqueous dispersion with the oil continuous phase to produce a water-in-oil emulsion containing water droplets. In an eighth embodiment, the method of embodiment 6 includes providing an aqueous continuous phase and mixing the oil dispersion with the continuous phase to produce an oil-in-water emulsion containing oil droplets.

[0064] In a ninth embodiment, the method of any one of embodiments 6 to 8 includes collecting the droplets. In a tenth embodiment, the method of embodiment 9 includes drying the droplets to obtain polymer-templated microspheres comprising the polymer nanospheres and the metal oxide, and removing the polymer nanospheres from the template microspheres.

[0065] In an eleventh embodiment, the method of any one of embodiments 6 to 10, wherein drying the droplets comprises microwave irradiation, oven drying, vacuum drying, drying in the presence of a desiccant, or a combination thereof.

[0066] In a twelfth embodiment, the method of any one of embodiments 7 to 11, wherein the oil phase or dispersion comprises a hydrocarbon, silicone oil, or fluorinated oil. In a thirteenth embodiment, the method of any one of embodiments 6 to 12, wherein the droplet formation occurs in a microfluidic device. In a fourteenth embodiment, the method of any one of embodiments 6 to 13, wherein the droplet formation occurs in a microfluidic device containing a droplet junction having a channel width of from about 10 μm, about 15 μm, about 20 μm, about 25 μm, about 30 μm, about 35 μm, about 40 μm, or about 45 μm to about 50 μm, about 55 μm, about 60 μm, about 65 μm, about 70 μm, about 75 μm, about 80 μm, about 85 μm, about 90 μm, about 95 μm, or about 100 μm. In a fifteenth embodiment, the method of any one of embodiments 13 or 14, comprising collecting the droplets from the microfluidic device.

[0067] In a sixteenth embodiment, the method of any of the preceding embodiments, wherein the wt / wt ratio of polymeric nanoparticles to metal oxide is from any of about 0.1 / 1, about 0.5 / 1, about 1.0 / 1, about 1.5 / 1, about 2.0 / 1, about 2.5 / 1, or about 3.0 / 1, to any of about 3.5 / 1, about 4.0 / 1, about 5.0 / 1, about 5.5 / 1, about 6.0 / 1, about 6.5 / 1, about 7.0 / 1, about 8.0 / 1, about 9.0 / 1, or about 10.0 / 1.

[0068] In a seventeenth embodiment, the method of any of the preceding embodiments, wherein the polymeric nanoparticles 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.

[0069] In an eighteenth embodiment, the method of any of the preceding embodiments, wherein the polymer is selected from the group consisting of poly(meth)acrylic acid, poly(meth)acrylate, polystyrene, polyacrylamide, polyethylene, polypropylene, polylactic acid, polyacrylonitrile, derivatives thereof, salts thereof, copolymers thereof, and combinations thereof.

[0070] In a nineteenth embodiment, the method of any of the preceding embodiments, wherein the polymer is selected from the group consisting of polystyrene copolymers, such as polystyrene / acrylic acid, polystyrene / poly(ethylene glycol) methacrylate, or polystyrene / styrene sulfonate. In a twentieth embodiment, the method of any of the preceding embodiments, wherein the metal oxide is one or more of silica, titania, alumina, zirconia, ceria, iron oxide, zinc oxide, indium oxide, tin oxide, or chromium oxide.

[0071] In a twenty-first embodiment, the method of any of the preceding embodiments, wherein the porous microspheres have an average diameter of about 0.5 μm to about 100 μm, an average porosity of about 0.10 to about 0.90 or about 0.10 to about 0.80, and an average pore size of about 50 nm to about 999 nm.

[0072] In a twenty-second embodiment, the method of any of the preceding embodiments, wherein the porous microspheres have an average diameter of about 1 μm to about 75 μm, about 2 μm to about 70 μm, about 3 μm to about 65 μm, about 4 μm to about 60 μm, about 5 μm to about 55 μm, or about 5 μm to about 50 μm; for example, from any of about 5 μm, about 6 μm, about 7 μm, about 8 μm, about 9 μm, about 10 μm, about 11 μm, about 12 μm, about 13 μm, about 14 μm, or about 15 μm, to any of about 16 μm, about 17 μm, about 18 μm, about 19 μm, about 20 μm, about 21 μm, about 22 μm, about 23 μm, about 24 μm, or about 25 μm.

[0073] In a twenty-third embodiment, the porous microspheres are of a molecular weight 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 0.51, about 0.52, about 0.53, about 0.54, about 0.55, about 0.56, about 0.57, about 0.58, about 0.59, about 100, about 101, about 102, about 103, about 104, about 105, about 106, about 107, about 108, about 109, about 110, about 111, about 112, about 113, about 114, about 115, about 116, about 117, about 118, about 119, about 120, about 121, about 122, about 123, about 124, about 125, about 126, about 127, about 128, about 129, about 130, about 131, about 132, about 133, about 134, about 135, about 136, about 137, about 138, about 139, about 140, about 141, about 142, about 143, about 144, about 145, about 146, about The method of any of the preceding embodiments, wherein the average porosity is from about 0.50, about 0.52, about 0.54, about 0.56, about 0.58, or about 0.60 to 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.

[0074] In a twenty-fourth embodiment, the porous microspheres are about 50 nm, about 60 nm, about 70 nm, 80 nm, 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. 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.

[0075] In a twenty-fifth embodiment, the method of any of the preceding embodiments, wherein the porous microspheres have an average diameter of from about 4.5 μm, about 4.8 μm, about 5.1 μm, about 5.4 μm, about 5.7 μm, about 6.0 μm, about 6.3 μm, about 6.6 μm, about 6.9 μm, about 7.2 μm, or about 7.5 μm to about 7.8 μm, about 8.1 μm, about 8.4 μm, about 8.7 μm, about 9.0 μm, about 9.3 μm, about 9.6 μm, or about 9.9 μm.

[0076] In a twenty-sixth embodiment, the method of any of the preceding embodiments, wherein the porous microspheres 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.

[0077] In a twenty-seventh embodiment, the method of any of the preceding embodiments, wherein the porous microspheres have an average pore size of from about 220 nm, about 225 nm, about 230 nm, about 235 nm, about 240 nm, about 245 nm, or about 250 nm to 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.

[0078] In a twenty-eighth embodiment, the porous microspheres have an average diameter of about 4.5 μm, about 4.8 μm, about 5.1 μm, about 5.4 μm, about 5.7 μm, about 6.0 μm, about 6.3 μm, about 6.6 μm, about 6.9 μm, about 7.2 μm, or about 7.5 μm to about 7.8 μm, about 8.1 μm, about 8.4 μm, about 8.7 μm, about 9.0 μm, about 9.3 μm, about 9.6 μm, or about 9.9 μm; about 0.45, about 0.47, about 0.49, about 0.51, about 0.53, about 0.55, or and an average pore diameter 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.

[0079] In a twenty-ninth embodiment, the method of any of the preceding embodiments, wherein the porous microspheres comprise from about 60.0 wt% to about 99.9 wt% metal oxide, for example, from 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 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 microsphere.

[0080] In a thirtieth embodiment, the porous microspheres comprise from about 0.1 wt % to about 40.0 wt % of one or more light absorbing agents, based on the total weight of the microsphere, for example, about 0.1 wt %, about 0.3 wt %, about 0.5 wt %, about 0.7 wt %, about 0.9 wt %, about 1.0 wt %, about 1.5 wt %, about 2.0 wt %, about 2.5 wt %, about 5.0 wt %, about 7.5 wt %, about 10.0 wt %. , about 13.0 wt%, about 17.0 wt%, about 20.0 wt%, or about 22.0 wt%, to about 24.0 wt%, about 27.0 wt%, about 29.0 wt%, about 31.0 wt%, about 33.0 wt%, about 35.0 wt%, about 37.0 wt%, about 39.0 wt%, or about 40.0 wt% of the one or more light absorbers.

[0081] In a thirty-first embodiment, the method of any of the preceding embodiments, wherein the porous microspheres comprise one or more light absorbers selected from the group consisting of inorganic pigments and organic pigments, such as carbon black.

[0082] In a 32nd embodiment, the method of any of the preceding embodiments, wherein a bulk sample of the porous microspheres exhibits a color that is observable by the human eye. In a 33rd embodiment, the method of any of the preceding embodiments, wherein a bulk sample of the porous microspheres exhibits an angle-independent color that is observable by the human eye. In a 34th embodiment, the method of any of the preceding embodiments, wherein a bulk sample of the porous microspheres exhibits an angle-dependent color that is observable by the human eye.

[0083] In a thirty-fifth embodiment, the method of any of the preceding embodiments, wherein the porous microspheres are monodisperse. In a thirty-sixth embodiment, the method of any of the preceding embodiments, wherein the porous metal oxide microspheres are a bulk sample of microspheres.

[0084] In a thirty-seventh embodiment, the method of any of the preceding embodiments, wherein removing the polymer nanospheres from the template microspheres comprises calcination, pyrolysis, or solvent removal.

[0085] In a thirty-eighth embodiment, the method of any of the preceding embodiments, wherein removing the polymer nanospheres comprises calcining the template microspheres at a temperature of from about 200°C, about 350°C, about 400°C, 450°C, about 500°C, or about 550°C to about 600°C, about 650°C, about 700°C, or about 1200°C for a time period of from about 0.1 hours, 1 hour, about 1.5 hours, about 2.0 hours, about 2.5 hours, about 3.0 hours, about 3.5 hours, or about 4.0 hours to about 4.5 hours, about 5.0 hours, about 5.5 hours, about 6.0 hours, about 6.5 hours, about 7.0 hours, about 7.5 hours, about 8.0 hours, or about 12 hours. Alternatively, calcination can be carried out at a temperature of at least about 200° C., at least about 500° C., or at least about 1000° C. for a suitable period of time, such as at least about 0.1 hours, at least about 1 hour, at least about 5 hours, or at least about 10 hours.

[0086] In a thirty-ninth embodiment, porous microspheres produced by any of the preceding methods are disclosed. In a fortieth embodiment, bulk samples of porous microspheres produced by any of the preceding methods are disclosed.

[0087] A second non-limiting set of embodiments of the present invention relating to porous metal oxide microspheres includes the following.

[0088] In a first embodiment, the microspheres comprise a metal oxide, the microspheres having an average diameter of about 0.5 μm to about 100 μm, an average porosity of about 0.10 to about 0.90 or about 0.10 to about 0.80, and an average pore size of about 50 nm to about 999 nm.

[0089] In a second embodiment, the porous microspheres of embodiment 1 are disclosed, having an average diameter of about 1 μm to about 75 μm, about 2 μm to about 70 μm, about 3 μm to about 65 μm, about 4 μm to about 60 μm, about 5 μm to about 55 μm, or about 5 μm to about 50 μm; for example, from about 5 μm, about 6 μm, about 7 μm, about 8 μm, about 9 μm, about 10 μm, about 11 μm, about 12 μm, about 13 μm, about 14 μm, or about 15 μm, to about 16 μm, about 17 μm, about 18 μm, about 19 μm, about 20 μm, about 21 μm, about 22 μm, about 23 μm, about 24 μm, or about 25 μm.

[0090] In a third embodiment, the hydroxyl group is 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 3. The porous microsphere of embodiment 1 or 2, having an average porosity of from about 0.54, about 0.56, about 0.58, or about 0.60 to 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.

[0091] In a fourth embodiment, the wavelength is from about 50 nm, about 60 nm, about 70 nm, about 80 nm, 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. , 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.

[0092] In a fifth embodiment, the porous microsphere of any of the preceding embodiments has an average diameter of from about 4.5 μm, about 4.8 μm, about 5.1 μm, about 5.4 μm, about 5.7 μm, about 6.0 μm, about 6.3 μm, about 6.6 μm, about 6.9 μm, about 7.2 μm, or about 7.5 μm to about 7.8 μm, about 8.1 μm, about 8.4 μm, about 8.7 μm, about 9.0 μm, about 9.3 μm, about 9.6 μm, or about 9.9 μm. In a sixth embodiment, the porous microsphere of any of the preceding embodiments has an average porosity of from about 0.45, about 0.47, about 0.49, about 0.51, about 0.53, about 0.55, or about 0.57 to about 0.59, about 0.61, about 0.63, or about 0.65. In a seventh embodiment, the porous microsphere of any of the preceding embodiments has an average pore size of from about 220 nm, about 225 nm, about 230 nm, about 235 nm, about 240 nm, about 245 nm, or about 250 nm to 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.

[0093] In an eighth embodiment, an average diameter from any of about 4.5 μm, about 4.8 μm, about 5.1 μm, about 5.4 μm, about 5.7 μm, about 6.0 μm, about 6.3 μm, about 6.6 μm, about 6.9 μm, about 7.2 μm, or about 7.5 μm to any of about 7.8 μm, about 8.1 μm, about 8.4 μm, about 8.7 μm, about 9.0 μm, about 9.3 μm, about 9.6 μm, or about 9.9 μm; any of about 0.45, about 0.47, about 0.49, about 0.51, about 0.53, about 0.55, or about 0.57 and an average pore size from about 220 nm, about 225 nm, about 230 nm, about 235 nm, about 240 nm, about 245 nm, or about 250 nm to 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.

[0094] In a ninth embodiment, the porous microsphere of any of the preceding embodiments comprises from about 60.0 wt% to about 99.9 wt% metal oxide, for example, from 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 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 microsphere.

[0095] In a tenth embodiment, the porous microsphere of any of the preceding embodiments, wherein the metal oxide 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. In an eleventh embodiment, the porous microsphere of any of the preceding embodiments, wherein the metal oxide is selected from the group consisting of silica, titania, alumina, and combinations thereof.

[0096] In a twelfth embodiment, the microspheres contain from about 0.1 wt % to about 40.0 wt % of one or more light absorbing agents, based on the total weight of the microspheres, for example, about 0.1 wt %, about 0.3 wt %, about 0.5 wt %, about 0.7 wt %, about 0.9 wt %, about 1.0 wt %, about 1.5 wt %, about 2.0 wt %, about 2.5 wt %, about 5.0 wt %, about 7.5 wt %, about 10.0 wt %, about 13.0 wt %, The porous microsphere of any of the preceding embodiments, comprising from about 17.0 wt%, about 20.0 wt%, or about 22.0 wt%, to about 24.0 wt%, about 27.0 wt%, about 29.0 wt%, about 31.0 wt%, about 33.0 wt%, about 35.0 wt%, about 37.0 wt%, about 39.0 wt%, or about 40.0 wt% of one or more light absorbing agents. In a thirteenth embodiment, the porous microsphere of any of the preceding embodiments, comprising one or more light absorbing agents selected from the group consisting of inorganic pigments and organic pigments, such as carbon black.

[0097] In a fourteenth embodiment, the porous microsphere of any of the preceding embodiments, wherein a bulk sample of the porous microsphere exhibits a color observable by the human eye. In a fifteenth embodiment, the porous microsphere of any of the preceding embodiments, wherein a bulk sample of the porous microsphere exhibits an angle-independent color observable by the human eye. In a sixteenth embodiment, the porous microsphere of any of the preceding embodiments, wherein a bulk sample of the porous microsphere exhibits an angle-dependent color observable by the human eye.

[0098] In a seventeenth embodiment, the porous microspheres of any of the preceding embodiments are monodisperse. In an eighteenth embodiment, a composition comprising a substrate and the porous microspheres of any of the preceding embodiments. In a nineteenth embodiment, the composition of embodiment 18 is an aqueous formulation, an oil-based formulation, an ink, a coating formulation, a food, a plastic, a cosmetic formulation, or a material for medical or security applications.

[0099] A third non-limiting set of embodiments of the present disclosure relating to porous metal oxide microspheres includes the following.

[0100] In a first embodiment, porous microspheres comprising a metal oxide are disclosed, wherein a bulk sample of the porous microspheres exhibits a color observable by the human eye.

[0101] In a second embodiment, the porous microspheres of embodiment 1 have an average diameter of about 0.5 μm to about 100 μm, an average porosity of about 0.10 to about 0.90 or about 0.10 to about 0.80, and an average pore size of about 50 nm to about 999 nm.

[0102] In a third embodiment, the porous microspheres of embodiment 1 or 2 have an average diameter of about 1 μm to about 75 μm, about 2 μm to about 70 μm, about 3 μm to about 65 μm, about 4 μm to about 60 μm, about 5 μm to about 55 μm, or about 5 μm to about 50 μm; for example, from about 5 μm, about 6 μm, about 7 μm, about 8 μm, about 9 μm, about 10 μm, about 11 μm, about 12 μm, about 13 μm, about 14 μm, or about 15 μm, to about 16 μm, about 17 μm, about 18 μm, about 19 μm, about 20 μm, about 21 μm, about 22 μm, about 23 μm, about 24 μm, or about 25 μm.

[0103] In a fourth embodiment, the hydroxyl group is 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 The porous microsphere of any of the preceding embodiments, having an average porosity of from any of 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.

[0104] In a fifth embodiment, the wavelength is from about 50 nm, about 60 nm, about 70 nm, about 80 nm, 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. , 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.

[0105] In a sixth embodiment, the porous microsphere of any of the preceding embodiments has an average diameter of from about 4.5 μm, about 4.8 μm, about 5.1 μm, about 5.4 μm, about 5.7 μm, about 6.0 μm, about 6.3 μm, about 6.6 μm, about 6.9 μm, about 7.2 μm, or about 7.5 μm to about 7.8 μm, about 8.1 μm, about 8.4 μm, about 8.7 μm, about 9.0 μm, about 9.3 μm, about 9.6 μm, or about 9.9 μm. In a seventh embodiment, the porous microsphere of any of the preceding embodiments has an average porosity of from about 0.45, about 0.47, about 0.49, about 0.51, about 0.53, about 0.55, or about 0.57 to about 0.59, about 0.61, about 0.63, or about 0.65. In an eighth embodiment, the porous microsphere of any of the preceding claims has an average pore size of from about 220 nm, about 225 nm, about 230 nm, about 235 nm, about 240 nm, about 245 nm, or about 250 nm to 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.

[0106] In a ninth embodiment, an average diameter of from about 4.5 μm, about 4.8 μm, about 5.1 μm, about 5.4 μm, about 5.7 μm, about 6.0 μm, about 6.3 μm, about 6.6 μm, about 6.9 μm, about 7.2 μm, or about 7.5 μm to about 7.8 μm, about 8.1 μm, about 8.4 μm, about 8.7 μm, about 9.0 μm, about 9.3 μm, about 9.6 μm, or about 9.9 μm; or any of about 0.45, about 0.47, about 0.49, about 0.51, about 0.53, about 0.55, or about 0.57. and an average pore size from about 220 nm, about 225 nm, about 230 nm, about 235 nm, about 240 nm, about 245 nm, or about 250 nm to 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.

[0107] In a tenth embodiment, the porous microsphere of any of the preceding embodiments comprises from about 60.0 wt% to about 99.9 wt% metal oxide, for example, from 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 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 microsphere.

[0108] In an eleventh embodiment, the porous microsphere of any of the preceding embodiments, wherein the metal oxide 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. In a twelfth embodiment, the porous microsphere of any of the preceding embodiments, wherein the metal oxide is selected from the group consisting of silica, titania, alumina, and combinations thereof.

[0109] In a thirteenth embodiment, the microspheres contain from about 0.1 wt % to about 40.0 wt % of one or more light absorbing agents, based on the total weight of the microspheres, for example, about 0.1 wt %, about 0.3 wt %, about 0.5 wt %, about 0.7 wt %, about 0.9 wt %, about 1.0 wt %, about 1.5 wt %, about 2.0 wt %, about 2.5 wt %, about 5.0 wt %, about 7.5 wt %, about 10.0 wt %, about 13.0 wt %, In a fourteenth embodiment, the porous microsphere of any of the preceding embodiments further comprises one or more light absorbing agents selected from the group consisting of inorganic pigments and organic pigments, such as carbon black.

[0110] In a sixteenth embodiment, the porous microsphere of any of the preceding embodiments, wherein a bulk sample of the porous microsphere exhibits a color observable by the human eye.

[0111] In a seventeenth embodiment, the porous microsphere of any of the preceding embodiments is monodisperse.

[0112] In an eighteenth embodiment, the porous microsphere of any of the preceding embodiments, wherein a bulk sample of the porous microsphere exhibits an angle-independent color that is observable by the human eye. In a nineteenth embodiment, the porous microsphere of any of the preceding embodiments, wherein a bulk sample of the porous microsphere exhibits an angle-dependent color that is observable by the human eye.

[0113] In a twentieth embodiment, a composition comprising a substrate and the porous microspheres of any of the preceding embodiments. In a twenty-first embodiment, the composition of embodiment 20 is an aqueous formulation, an oil-based formulation, a coating formulation, a food, an ink, a plastic, a cosmetic formulation, or a material for medical or security applications.

[0114] Example Example 1 Porous Silica Microspheres Styrene / acrylic acid copolymer is prepared as follows: 230 mL of deionized (DI) water is placed in a three-neck reaction flask equipped with a thermometer, condenser, magnetic stirrer, and nitrogen atmosphere. The water is heated to 80°C, and 10 g of styrene is added with stirring, followed by 100 mg of acrylic acid dissolved in 10 mL of DI water via syringe. 100 mg of ammonium persulfate is dissolved in 10 mL of DI water and added to the stirred mixture via syringe. The reaction mixture is stirred at 80°C for 24 hours. The polymer colloidal dispersion is allowed to cool to room temperature and purified by centrifugation to produce polystyrene nanospheres with an average particle size of 250 nm.

[0115] An aqueous polystyrene colloidal dispersion is diluted to 1 wt% with deionized water, 1 wt% silica nanoparticles are added, and the mixture is sonicated to prevent particle aggregation. The oil continuous phase contains 0.1 wt% polyethylene glycol / perfluoropolyether surfactant in fluorinated oil. The aqueous colloidal dispersion and oil are each injected into a microfluidic device with a 50 μm droplet junction using a syringe connected to a pump. The system is left to equilibrate until monodisperse droplets are formed. The monodisperse droplets are collected in a reservoir.

[0116] The collected droplets are dried in an oven at 45°C for 4 hours to yield monodisperse polymer-templated microspheres. The polymer-templated microspheres are calcined by placing them on a silicon wafer and heating from room temperature to 500°C over 3 hours, holding at 500°C for 2 hours, and then cooling back to room temperature over 3 hours. Monodisperse silica microspheres with an average diameter of 15 microns are obtained.

[0117] Figures 2 and 3 are scanning electron microscope (SEM) images of polymer-templated microspheres and porous silica microspheres prepared in a similar manner.

[0118] Example 2 Porous Silica Microspheres Containing Light Absorbers The product of Example 1 is physically mixed with different weight levels of carbon black aqueous dispersion or carbon black powder to obtain monodisperse porous silica microspheres containing carbon black at levels of 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, and 5 wt% based on the total weight of the microspheres.

[0119] Example 3 Drying Method Examples 1 and 2 are repeated, where the drying step uses microwave irradiation, vacuum drying, and / or drying in the presence of a desiccant.

[0120] Example 4 Preparation of porous silica microspheres by spray drying Styrene / acrylic acid copolymer is prepared as follows: 230 mL of deionized (DI) water is placed in a three-neck reaction flask equipped with a thermometer, condenser, magnetic stirrer, and nitrogen atmosphere. The water is heated to 80°C, and 10 g of styrene is added with stirring, followed by 100 mg of acrylic acid dissolved in 10 mL of DI water via syringe. 100 mg of ammonium persulfate is dissolved in 10 mL of DI water and added to the stirred mixture via syringe. The reaction mixture is stirred at 80°C for 24 hours. The polymer colloidal dispersion is allowed to cool to room temperature and purified by centrifugation to produce polystyrene nanospheres with an average particle size of 250 nm.

[0121] An aqueous polystyrene colloidal dispersion is diluted to 1 wt% with deionized water, 1 wt% silica nanoparticles are added, and the mixture is sonicated to prevent particle aggregation. The aqueous dispersion is spray-dried to obtain polymer-templated microspheres containing polymer nanospheres and silica. The microspheres are calcined by heating from room temperature to 500°C over 3 hours, holding at 500°C for 2 hours, and then returning to room temperature over 3 hours. Porous silica microspheres are obtained.

[0122] Example 5. Visible color of bulk samples In these bulk color examples, 6cm 2 0.5 milligrams of porous microspheres are evenly placed in a 10 mL clear glass vial with a base area of ​​1.5 mm. The color is observed with the human eye.

[0123] Two samples of porous silica microspheres were prepared similarly to Example 1, where the wt / wt ratio of polymer to silica was 1:1 and 3:1, respectively. The 1:1 wt / wt sample was white, while the 3:1 wt / wt sample was distinctly blue.

[0124] A sample of porous silica microspheres was prepared according to Example 1, where the polystyrene nanospheres have an average particle size of 360 nm and a polymer to silica wt / wt ratio of 3:1. The sample exhibits a distinct green color.

[0125] Porous silica microspheres were prepared as in Example 4, where the polystyrene nanospheres had an average particle size of 360 nm. When the wt / wt ratio of polymer to silica was 4:1, the porous microspheres had a porosity of 0.55 and a distinct green color. When the wt / wt ratio of polymer to silica was 2:1, the porous microspheres had a porosity of 0.45 and a distinct orange color.

[0126] Example 6 Zinc Oxide Porous Microspheres A sample of porous zinc oxide microspheres is prepared according to the procedure of Example 4, except that silica is replaced with zinc oxide, the polystyrene nanospheres have an average particle size of 230 nm, and the wt / wt ratio of polymer to zinc oxide is 1:2. 2 A 0.5 mg sample of porous microspheres is evenly placed in a 10 mL clear glass vial having a base area of ​​0.5 mg. This sample appears a distinct blue color to the human eye.

[0127] Example 7 Silica / Titania Porous Microspheres A sample of porous microspheres containing silica and titania was prepared according to the process of Example 1, where the wt / wt ratio of polymer to total metal oxide is 3:1. The wt / wt ratio of silica to titania is 9:1.

Claims

1. 1. A method for producing porous metal oxide microspheres comprising a metal oxide, comprising: preparing a dispersion of polymer nanoparticles and metal oxide; producing droplets of said dispersion; drying the droplets to obtain polymer-templated microspheres comprising polymer nanospheres and metal oxide; and removing the polymer nanospheres from the template microspheres to obtain the porous metal oxide microspheres; Including, The microspheres are an average diameter of about 0.5 μm to about 100 μm; an average porosity of about 0.10 to about 0.80; and The method has an average pore size of about 50 nm to about 999 nm.

2. 10. The method of claim 1, comprising preparing a dispersion of polymeric nanoparticles and the metal oxide, spray drying the dispersion to obtain polymeric template microspheres, and removing the polymeric nanospheres from the template microspheres.

3. The method of claim 1 , comprising producing the droplets with a vibrating nozzle.

4. The method of claim 1 , wherein the droplets are water droplets or oil droplets.

5. 10. The method of claim 1, comprising providing a continuous phase, mixing said dispersion with said continuous phase to produce an emulsion containing dispersed droplets, and collecting said droplets.

6. The method of claim 5, further comprising drying the droplets to obtain polymeric template microspheres comprising polymeric nanospheres and metal oxide, and removing the polymeric nanospheres from the template microspheres.

7. 7. The method of claim 6, wherein drying the droplets comprises microwave irradiation, oven drying, vacuum drying, drying in the presence of a desiccant, or a combination thereof.

8. The method of claim 5 , wherein the droplets are formed in a microfluidic device.

9. 9. The method of any one of claims 1 to 8, wherein the wt / wt ratio of the polymeric nanoparticles to the metal oxide is from about 0.5 / 1 to about 10.0 / 1.

10. The method of any one of claims 1 to 8, wherein the polymeric nanoparticles have an average diameter of from about 50 nm to about 990 nm.

11. 9. The method of any one of claims 1 to 8, wherein the polymer is selected from the group consisting of poly(meth)acrylic acid, poly(meth)acrylate, polystyrene, polyacrylamide, polyethylene, polypropylene, polylactic acid, polyacrylonitrile, derivatives thereof, salts thereof, copolymers thereof, and combinations thereof.

12. 9. The method of any one of claims 1 to 8, wherein the metal oxide 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.

13. 9. The method of any one of claims 1 to 8, wherein the porous microspheres are monodisperse.

14. 9. The method of claim 1, wherein the porous metal oxide microspheres are a bulk sample of microspheres.

15. 9. The method of claim 1, wherein removing the polymer nanospheres from the template microspheres comprises calcination, pyrolysis, or solvent removal.

16. 9. The method of any one of claims 1 to 8, wherein removing the polymer nanospheres comprises calcining the template microspheres at a temperature of about 350°C to about 700°C for about 1 hour to about 8 hours.

17. 9. Porous microspheres produced according to any one of claims 1 to 8.

18. A bulk sample of porous microspheres produced according to any one of claims 1 to 8.

19. 1. A porous microsphere comprising a metal oxide, an average diameter of about 1 μm to about 75 μm; an average porosity of about 0.45 to about 0.65; and having an average pore size of about 50 nm to about 800 nm; Microsphere.

20. 10. The porous microsphere of claim 1, having an average diameter of about 1 μm to about 75 μm.

21. 10. The porous microsphere of claim 1, having an average pore size of about 50 nm to about 800 nm.

22. 10. The porous microsphere of claim 1, having an average porosity of about 0.45 to about 0.

65.

23. an average diameter of about 4.5 μm to about 9.9 μm; an average porosity of about 0.45 to about 0.65; and having an average pore size of about 220 nm to about 300 nm; 20. The porous microsphere of claim 19.

24. 24. The porous microsphere of any one of claims 19 to 23, comprising about 60.0 wt% to about 99.9 wt% metal oxide based on the total weight of the microsphere.

25. 24. The porous microsphere of any one of claims 19 to 23, wherein the metal oxide 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.

26. 24. The porous microsphere of any one of claims 19 to 23, comprising from about 0.1 wt% to about 40.0 wt% of one or more light absorbing agents, based on the total weight of the microsphere.

27. 24. The porous microsphere of any one of claims 19 to 23, wherein a bulk sample of the porous microsphere exhibits a color observable by the human eye.

28. 24. The porous microsphere of any one of claims 19 to 23, which is monodisperse.

29. A composition comprising a substrate and a porous microsphere according to any one of claims 19 to 23.

30. 30. The composition of claim 29, which is a water-based formulation, an oil-based formulation, an ink, a coating formulation, a food, a plastic, a cosmetic formulation, or a material for medical or security applications.

31. A porous microsphere comprising a metal oxide, wherein a bulk sample of said porous microsphere exhibits a color observable by the human eye.

32. 32. The porous microsphere of claim 31, wherein a bulk sample of said porous microsphere exhibits an angle-independent color observable by the human eye.

33. 32. The porous microsphere of claim 31, wherein a bulk sample of said porous microsphere exhibits an angle-dependent color observable by the human eye.

34. 34. A composition comprising a substrate and a porous microsphere according to any one of claims 31 to 33.

35. 35. The composition of claim 34, which is an aqueous formulation, an oil-based formulation, a coating formulation, a food, an ink, a plastic, a cosmetic formulation, or a material for medical or security applications.

Images