VO2@SiO2/Poly(N-isopropylacrylamide) Hybrid Nanothermochromic Microgels for Smart Window

VO2/PNIPAm hybrid thermochromic material has been verified as promising to improve optical performance of smart windows. However, VO2 can be easily oxidized especially when being dispersed in the hydrogel matrix, and also the nonuniform dispersion of VO2 in a host will worsen the material's optical performance. Herein, pure VO2(M)@SiO2 nanoparticles (NPs) were first prepared using a surfactant-free method. Then VO2(M)@SiO2/PNIPAm hybrid microgels were synthesized through suspension polymerization. The VO2(M)@SiO2 NPs in the hydrogel matrix exhibited obviously improved resistance to oxidation. Monodispersed hybrid microgel with uniformly distributed VO2(M)@SiO2 NPs (Sample I) was obtained. Meanwhile, compared with the best VO2 film reported, our composite microgel (Sample III) demonstrated a 164% increase in the solar modulating ability at a relatively high average luminous transmittance (38.4%). All these remarkable features of VO2(M)@SiO2/PNIPAm microgel synthesized in our work will help a lot in the practical application of the inorganic-organic hybrid nanothermochromic materials.