In situ preparation of VO₂@PMMA microcapsule and thermochromic properties of its coating

Vanadium dioxide (VO₂) can change infrared transmittance in response to external temperature changes, and has become the preferred material for thermochromic smart windows. The facile ball milling method is simple, easy to operate, short reaction time, less pollution, suitable for industrial production. However, there are still some problems with vanadium dioxide that may hinder large scale production and practical applications, such as poor stability and easily agglomeration. Here we report on the preparation of thermochromic coating based on VO₂@polymethyl methacrylate (PMMA) microcapsule synthesized through in-situ polymerized method. Uniform VO₂@PMMA microcapsules was obtained by in situ polymerization of double bonds on the surface of VO₂ and methyl methacrylate (MMA) monomer. The space barrier effect of in-situ polymerized PMMA is used to prevent VO₂ agglomeration. With good compactness PMMA prevent air and moisture from contacting VO₂, which improve VO₂ stability. VO₂@PMMA films prepared by a roll coating method not only has good acid resistance and oxidation resistance, but also has excellent optical properties with the solar modulation efficiency (ΔT_sol) 10.12% at 77.89% visible light transmittance (T_lum), which meets the application requirements of smart windows.