Low-cost and fast thermal response Mo-PVA/PNIPAM hydrogel based smart window for monitoring indoor temperature under hot environment

Abstract

In recent years, global warming has precipitated a series of challenges to human living comfort. While some techniques can offer mitigation, their energy-intensive nature renders them unsuitable for widespread adoption in underdeveloped regions. To address these shortcomings, a cost-effective smart window with indoor temperature regulation was developed. It was fabricated by integrating {Mo154} with a blend of polyvinyl alcohol/poly(N-isopropyl acrylamide) (PVA/PNIPAM) hydrogel. Based on the temperature induced phase transformation ability of PNIPAM, the composite hydrogel can be used to regulate the indoor temperature. Concurrently, PVA can mitigate the problem of volume shrinkage from PNIPAM phase transition. More importantly, the {Mo154} can reduce the lower critical solution temperature (LCST) of Mo-PVA/PNIPAM hydrogel, as well as provide photothermal properties for intelligently sensing the outside temperature. The smart window can display a favorable sunlight modulation property (ΔTsol = 80.8%) and a rapid heating rate response to light exposure. Due to the presence of the {Mo154}, the smart window became opaque to block sunlight when the indoor temperature exceeded 28.9 oC. This feature can keep indoor cooling in the hot summer without any energy consumption. Moreover, the Mo-PVA/PNIPAM-based smart window also demonstrated favorable durability, maintaining its functionality after 100 times heating (40 oC)-cooling (20 oC) cycles, which can support long time usage and suit for the underdeveloped areas with limited electric energy.