Precision-Engineered Thermochromic Hydrogels: Achieving High Optical Clarity and Antishrinkage in Solar Modulation

Abstract

Energy-efficient smart windows, as pivotal components of a sustainable built environment, demand advanced soft materials with dynamic adjustability in thermochromic optical properties alongside durable structural integrity. However, current material systems fail to achieve the balance of high optical clarity, solar modulation capability, thermal responsiveness, and stability within a single material. Herein, we introduce a sponge bone needlelike architecture into poly(N-isopropylacrylamide) (PNIPAm) matrix, creating a tough gel with precise control over solar modulation and significant enhancement in structural stability. The methacrylic anhydride (MA) modification is prominent in forming this biomimetic architecture; thus, the rigid MA-grafted chains are responsible for the improved mechanical stability. The integration of methacrylic anhydride-grafted hyaluronic acid (HAMA) within the PNIPAm matrix leverages the rigid HAMA phase to reinforce the gel network, providing a robust scaffold that mitigates deformation even after extensive thermal cycling. Through the application of a random forest model and coregulation of synthesis parameters, we accurately predicted and controlled the phase transition temperature (τc) of the gel material, achieving an optical modulation efficiency exceeding 90% and antishrinkage properties for up to 500 cycles. Moreover, this smart hydrogel demonstrates temperature-regulation capabilities across diverse climatic zones, highlighting its potential for sustainable building solutions through energy-efficient thermal management and environmentally responsive material design. This material design strategy offers a novel approach to fabricating high-transparency, solar-modulating, thermally tunable, and stable smart hydrogels suitable for use in smart windows, sensors, and soft robots, thereby contributing to multifunctional uses in a low-carbon economy.