Thermal-responsive PNIPAm-acrylic/Ag NRs hybrid hydrogel with atmospheric window full-wavelength thermal management for smart windows

Smart windows with reversible regulation on solar radiation by altering their optical transmittance in response to thermal stimuli have been developed as a promising solution toward reducing energy consumption of buildings. This work presents a new strategy for doping Ag nanorods (NRs) with poly(N-isopropylacrylamide) (PNIPAm) hydrogel to achieve atmospheric window full-wavelength thermal management. PNIPAm as basic material was aimed to achieve solar radiation modulation among visible, near infrared (NIR), and middle infrared region. Acrylic was grafted on PNIPAm chains to enhance mechanical strength. While Ag NRs were the major factors that affected solar radiation modulation due to its structural changes driven by PNIPAm phase transition. The hybrid hydrogel showed a relatively high solar modulation ability (Delta T-sol) of 59.24% while maintaining luminous transmittance (T-lum) of 61.36% under room temperature. The infrared emissivity kept a little increase from 0.947 to 0.958 during phase transition and caused a 12.7 degrees C reduction in temperature observed from the water-warming experiment. The innovative combination of Ag NRs and hydrogel indicated that metal nanorods may make positive effects when combining with hydrogels. This kind of new strategy based on atmospheric window full-wavelength thermal management exhibits to be an ideal candidate for applications in smart windows.