Passively Driven Smart Windows Based on Oriented HPC/PAMPS Composite Hydrogel

Smart windows with adjustable optical properties for energy-saving applications have received increasing attention. In this study, an anisotropic single-domain structure is successfully prepared by shearing-oriented hydroxypropyl cellulose (HPC) in poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) hydrogel network. This composite hydrogel can respond to ambient temperature and solar radiation in the visible and near-infrared light regions for smart window applications. By precisely controlling the component of the composite hydrogel, the cloud point temperature ( T cp ) of the smart window can be significantly tuned from a very high value to below the comfortable temperature for the human body. For example, with 10 wt.% PAMPS and 42 wt.% HPC, the crosslinking hydrogel demonstrates a stable single-domain structure and relatively low T cp . With the addition of NaCl, T cp can be further reduced to even below the human comfort temperature. The oriented composite hydrogel showed excellent durability, flexibility, and thermal radiation shielding under the sunlight simulator with tunable T cp . These properties make the HPC/PAMPS composite hydrogel have a broad application prospect in the realm of energy-efficient building smart windows and effectively improve the comfort of indoor environments with different demands.