Combining Krafft Point and Volume Phase Transition Temperature Toward Regulation of Solar Radiation and Privacy Protection

Abstract

Everlasting pursuit of high energy efficiency as well as meeting fluctuant temperatures raise various lighting requirements, which is driving the originality of thermochromic smart windows (SWs). SWs with dual-temperature response upon rational designs are identified as an effective approach to regulate solar radiation and protect privacy. Here, combining the Krafft point (Tk) of ionic surfactants and the volume phase transition temperature (VPTT) of gels toward SW materials is utilized to achieve a transition of opacity-transparence-opacity as temperature change, maintaining transparency at an intermediate temperature range with favorable optical modulation parameters. Cationic surfactant, hexadecylpyridinium bromide (HPB), and poly(N-isopropylacrylamide) (PNIPAM) are combined using Tk and VPTT to serve as the dual thermo-responsive switches for regulating solar radiation and protecting privacy. Tk of HPB can be adjusted by adding salts and VPTT is turned by introducing hydrophilic and hydrophobic comonomer. This work provides a realizable pathway by which in situ adjustable parameters may be performed and operated in external environment conditions, completely changing the smart window materials.