UCLA

Thermally responsive smart window devices are gaining popular attention due to its ability to be dynamically tuned in response to changes in external temperature, serving to reduce energy consumption for cooling and heating systems. The optical state of the smart window device is adjusted that controls the extent at which the incident solar radiation is transmitted. A thermochromic phase-changing copolymer is introduced that consists of clear poly stearyl acrylate (CPSA) and poly(2-hydroxyethyl methacrylate) poly(HEMA). The synthesis process consists of a thermal-activated ultraviolet curing treatment with the use of ethoxylated trimethylolpropane triacrylate (ETPTA) crosslinker and 2,2-dimethoxy-2-phenylacetophenone (DMPA) photoinitiator. The crystallinity change of CPSA as it is heated to its phase transition temperature (Tc) of 42°C causes its refractive index to differ from that of poly(HEMA), resulting in the copolymer to switch from a transparent to an opaque state. At room temperature (20°C) and 80°C, the copolymer film has a visible transmittance of 91.9% and 3.6%, respectively, with a solar modulation (∆Tsolar) of 88.3%. The data measurements are gathered with the use of a UV-VIS spectrophotometer.