Phase-changing polymer film for thermochromic smart windows applications

Abstract

A solid state thermochromic polymer film comprising two or more separated solid phases with matched refractive indices, wherein the separated solid phases are transparent; and one of the phases undergoes a crystal melting above a threshold temperature resulting in significant reduction of its refractive index. The one of the phases undergoing the crystal melting becomes opaque when its temperature rises above said threshold temperature; and reverts to being transparent when its temperature lowers to an ambient temperature below said threshold temperature. In one example, the new thermochromic phase-changing copolymer with switchable optical transparency is fabricated via copolymerizing hydrophilic poly(hydroxyethyl acrylate) and hydrophobic poly(hexadecyl acrylate-tetradecyl acrylate). The polymer film is transparent due to matched refractive indices of the phase separated domains, but turns opaque when the long alkyl chains undergoes crystalline melting above 28-32° C. The transmittance modulation is autonomous and reversible.

Dependencies are inferred from the claim text.