Session: 03-02: Innovative Building Material and Technologies

Paper Number: 169792

169792 - Entropy-Engineered Polymer Aerogels Shatter Solar Reflectivity Limits 

Abstract: 

As global temperatures rise, the demand for cooling technologies is escalating, yet conventional methods exacerbate energy consumption and emissions. There is a pressing need for sustainable, energy-free cooling solutions. Existing materials often fall short due to performance and scalability limitations. This challenge necessitates innovative materials that can cool without energy input. Our work addresses this gap with a novel aerogel technology.

We present a groundbreaking method for fabricating polymer aerogels that eliminates energy-intensive supercritical drying, multi-solvent systems, and nanoparticles. By dissolving conjugated-backbone polymer in a single solvent (15 wt%), where the solvent evaporation triggers spinodal decomposition, creating a hierarchical structure with radially aligned macropores (5–20 µm) and a self-assembled nanofibrillar network (50 nm). The resulting aerogel achieves an exceptional 99.7% solar reflectivity through synergistic scattering and total internal reflection phenomena, coupled with a temperature reduction of 11°C below ambient, demonstrating its potential as an electricity-free cooling material. Its ultralow thermal conductivity (37 mW/mK at ambient, decreasing to 25 mW/mK at 200 °C) and mechanical durability—retaining properties after three days of T8 weather exposure in Hong Kong—position it as a durable building skin solution for hot climates. The material’s biodegradability, self-cleaning capability, and minimal UV-induced reflectivity loss (7% after 3 months) further enhance its sustainability profile. By passively offsetting cooling-related energy demands—a critical need as global cooling emissions rise, and urban heat islands intensify—this technology directly addresses decarbonization challenges.

Presenting Author: Muhammad Fahim City University of Hong Kong

Presenting Author Biography: Dr. Muhammad Fahim is a Postdoctoral researcher at the School of Energy and Environment, City University of Hong Kong. He holds a Ph.D. in Energy and Environment Engineering from City University of Hong Kong (2022). During his Ph.D., he served as a Research Assistant and Teaching Assistant. Currently, he is working under the supervision of Prof. Edwin Chi Yan Tso, focusing on passive radiative cooling and thermochromic smart windows. His research expertise includes perovskite solar cells, with a notable portfolio of 13 publications and one U.S.-filed patent.