Scalable method of fabricating structured polymers for passive daytime radiative cooling and other applications
A structured material is provided that includes a substrate and a porous structured polymer layer disposed thereon. The porous structured polymer layer includes a plurality of voids, and has a high hemispherical reflectance a high a hemispherical thermal emittance. The structured material is thus particularly advantageous for cool-roof coatings, enabling surfaces coated by the material to stay cool, even under strong sunlight. The material can be produced via structuring of polymers in a mixture including a solvent and a non-solvent. Sequential evaporation of the solvent and the non-solvent provide a polymer layer with the plurality of voids.
1. A composition, comprising:
an amount of a pore-forming agent, the pore-forming agent being curable to form a structure having a plurality of voids therein and arranged to facilitate reflecting solar radiation away from a surface covered by the structure and dissipate heat by thermal radiation;
a polar species; and
a non-polar species,
wherein the distribution of the pore-forming agent, the polar species, and the non-polar species in the composition is homogenous.
2. The composition of claim 1 , wherein the pore-forming agent comprises any one or more of poly(vinylidene difluoride), poly(vinylidene difluoride-co-hexafluoropropene), poly(methyl methacrylate), poly(vinyl chloride), poly(vinyl fluoride), poly(styrene), poly(dimethyl siloxane), poly(vinyl alcohol), ethyl-cellulose, methyl-cellulose, and cellulose acetate.
3. The composition of claim 2 , wherein the pore-forming agent comprises poly(vinylidene difluoride-co-hexafluoropropene).
4. The composition of claim 1 , wherein the structure is white in appearance.
5. The composition of claim 1 , further comprising a colorant.
6. The composition of claim 1 , wherein the polar species comprises at least one of water and ethanol.
7. The composition of claim 1 , wherein the voids have cross-sectional dimensions of less than 2 micrometers.
8. The composition of claim 1 , wherein the voids have cross-sectional dimensions between 20 nm to 700 nm.
9. The composition of claim 1 , wherein the voids have cross-sectional dimensions of from about 3 to about 20 micrometers.
10. The composition of claim 1 , wherein the structure is adapted to radiate heat at a wavelength of from about 8 to about 13 micrometers.
11. A method, comprising applying a composition according to claim 1 to a surface.
12. The method of claim 11 , wherein the applying comprises any one or more of spraying, painting, and dipping.
13. The method of claim 12 , wherein the applying comprises spraying.
14. The method of claim 11 , further comprising curing the composition so as to form the structure.
15. The method of claim 11 , wherein the voids have cross-sectional dimensions of less than 2 micrometers.
16. The method of claim 11 , wherein the voids have cross-sectional dimensions between 20 nm to 700 nm.
17. The method of claim 11 , wherein the voids have cross-sectional dimensions of from about 3 to about 20 micrometers.
18. The method of claim 11 , wherein the structure is adapted to radiate heat at a wavelength of from about 8 to about 13 micrometers.
19. A method, comprising: applying a composition comprising a pore-forming agent, a second species, and a third species to a substrate and effecting removal of the second species and the third species so as to give rise to a structure having a plurality of voids therein and arranged to facilitate reflecting solar radiation away from a surface covered by the structure and dissipate heat by thermal radiation,
wherein the second species is a polar species,
wherein the third species is a non-polar species, and
wherein the distribution of the pore-forming agent, the second species, and the third species in the composition is homogenous.
20. The method of claim 1 , wherein the voids have cross-sectional dimensions between 20 nm to 700 nm.