Multilayer Gradient <scp>PVA</scp> / <scp> SiO ₂ </scp> Aerogel Composites With Enhanced Thermal Insulation and Structural Integrity

ABSTRACT The growing demand for high‐efficiency thermal insulation materials in industrial and consumer sectors has driven the development of polymer–aerogel composites with tailored microstructures. In this work, poly(vinyl alcohol)/silica aerogel (PVA/SiO 2 ) gradient composites were fabricated via a facile hot‐press molding process and systematically evaluated for their thermal insulation behavior. Increasing the SiO 2 aerogel content from 5 to 15 wt% decreased the thermal conductivity of single‐layer composites from 55.6 to 50.3 mW m −1 K −1 , attributed to the formation of uniformly dispersed “thermal insulation islands” within the PVA matrix. Notably, the triple‐layer gradient composite exhibited an ultralow thermal conductivity of 28.9 mW m −1 K −1 , surpassing both single‐ and double‐layer structures due to the combined effects of hierarchical porosity and interfacial phonon scattering. Infrared thermography further confirmed excellent heat‐shielding capability, maintaining surface temperatures of only 55.4°C and 121.4°C under heating at 100°C and 200°C, respectively. These findings demonstrate that the gradient design strategy effectively integrates nanoscale porosity with interfacial thermal resistance, offering a promising pathway toward lightweight, high‐performance polymer/aerogel composites for advanced thermal management applications.