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

Abstract 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.