Thermochromic hydrogels for synergistic mechano-optical properties and global energy saving potential

Abstract

As building energy consumption and carbon emissions continue to rise, minimizing energy loss through windows—major heat exchange pathways—has become an urgent challenge. To reduce building energy consumption by improving windows’ thermal insulation and light modulation, this study develops a thermoresponsive hydrogel named PDH, based on a poly(N-isopropylacrylamide) backbone, for use as a window coating. The hydrogel exhibits considerable visible light transmittance (97.92%) and high solar modulation ability (81.70%), along with favorable mechanical properties, which enable its stable and direct application onto single-pane glass surface, thereby simplifying the conventional glass–hydrogel–glass structure in smart windows. In practical building applications, PDH hydrogel shows significant thermal regulation, with an average daytime indoor temperature reduction of 6.95 °C and energy savings of 384.04 kJ m−2. Furthermore, a global energy-saving and carbon-reduction model is developed using climate data to support the assessments and applications of PDH hydrogels across various climate regions.