Thermally conductive and hygroscopic poly(acrylamide-dimethylacrylamide) double-network hydrogel for effective heat dissipation

Maintaining optimal temperatures through effective heat dissipation is crucial across engineering and biological applications. While hydrogels offer excellent potential for passive evaporative cooling thanks to their high water content, poor durability and stability hinder their widespread adoption. We have engineered a robust poly(acrylamide-dimethylacrylamide) double-network hydrogel specifically designed to overcome these limitations. Key advancements include significantly enhanced water retention (indicated by higher water evaporation enthalpy) and superior mechanical strength, optimized with a 40:10 monomer-to-crosslinker ratio that ensures stability even after swelling. The introduction of a hygroscopic salt via rehydration of freeze-dried hydrogels in a CaCl 2 solution improved water absorption under high relative humidity, significantly improving durability. Furthermore, the incorporation of boron nitride (BN) nanosheets and carbon nanofibres (CNFs) increased the hydrogel's thermal conductivity, ensuring efficient heat transfer through platelet plus linear conducting routes. Our findings demonstrate that this novel composite hydrogel exhibits superior thermal performance, mechanical robustness, and long-term durability, making it a promising candidate for advanced thermal management applications such as wearable cooling devices, building cooling systems, and backsheet of photovoltaic panels. In particular, PV simulations show enhanced power output due to reduced surface temperature. • A robust poly(acrylamide-dimethylacrylamide) double-network hydrogel is specifically designed. • An optimal 40:10 monomer-to-crosslinker ratio leads to significantly enhanced water retention and mechanical strength. • Hygroscopic salt CaCl2 improves water absorption and enhances durability. • The incorporation of BN nanosheets and CNFs increases heat transfer through platelet plus linear conducting path.