UCLA

Thermochromic smart windows have emerged as a promising solution for passive energy management in buildings by dynamically regulating solar heat gain based on ambient temperature. This study introduces a solvent-free, thermally responsive copolymer system comprising poly(stearyl acrylate) (CPSA) and poly(2-hydroxyethyl methacrylate) (poly(HEMA)). The copolymer leverages the temperature-induced crystallinity transition of CPSA to trigger a refractive index mismatch with poly(HEMA), resulting in a reversible optical shift between transparent and opaque states. The film is fabricated using a UV-assisted thermal curing process with ethoxylated trimethylolpropane triacrylate (ETPTA) as the crosslinker and 2,2-dimethoxy-2-phenylacetophenone (DMPA) as the photoinitiator. Optimization of SA:HEMA ratio, UV curing temperature, and diethylene glycol (DEG) content led to an optical transmittance of 92.1% in the transparent state and 4.2% in the opaque state, yielding a solar modulation efficiency (ΔTsolar) of 88.3%. UV-VIS spectrophotometry was employed to characterize optical performance across temperature gradients. These results validate the potential of the CPSA–poly(HEMA) system as a tunable and scalable platform for energy-efficient smart window applications.