Temperature-responsive hydrogel with ultra-large solar modulation and high luminous transmission for “smart window” applications
The application of a thin film of poly(N-isopropylacrylmide) hydrogel to thermochromic smart windows has been investigated. As the thickness of the hydrogel increased from 26 to 200 μm and the testing temperature increased from 20 to 60 °C, the solar modulating ability (ΔTsol) increased and the luminous transmittance (Tlum) decreased. Compared with the best reported results for the most studied inorganic VO2 thermochromic coatings, an unprecedented good combination of near-doubled average Tlum (70.7% vs. 42.8%), higher ΔTsol (25.5% vs. 22.3%) and lower transition temperature (∼32 °C vs. ∼68 °C) could be achieved by hydrogels with an optimized thickness. Good durability and reversibility were established with the correct sealing of the sandwich structure.