Passive dimming phase change material inspired by polymer hydrogels

Abstract

As a new concept of smart materials, passive dimming phase change materials (PDPCMs) have potential in the field of energy-efficient buildings due to ultra-high energy utilization efficiency. Novel PDPCMs materials are reported by simulating the microstructure of high light transmittance polymer hydrogels. The self-prepared composite coordinates the inherent contradiction between anti liquid leakage, optical transmittance switching, and thermal storage density. There is an interaction between the hydroxyl groups (–OH) of MA and the ester groups (–COOR) of polybutylmethacrylate (PBMA), resulting in the PBMA/MA with a VMA/VPBMA volume ratio of 6:5 exhibiting good resistance to liquid leakage even when stretched to about 400 % at 60 °C. Based on the good compatibility and well-matched refractive index between MA and PBMA framework materials, the visible light transmittance of as-prepared PDPCMs has increased from 0.1 % at 30 °C to 89.0 % at 60 °C. The as-prepared composite also exhibits a good latent heat-storage capability with satisfactory phase-change enthalpies of over 113 J g−1. The as-prepared PDPCMs eliminate the spatial positional differences between photo-thermal conversion and thermal energy absorption, without considering the thermal conductivity of PDPCMs. The photo-thermal conversion efficiency can be increased by introducing well-matched color changing ink (CCI), significantly improving energy utilization efficiency. On the other hand, energy-saving doors/windows containing PBMA/MA composite materials allow sunlight to spread indoors due to the high transmittance (89.0 %) at high temperatures. The new design concept makes passive dimming composite materials suitable for high latitude areas.