Self-Healing Hydrogel-Based Form-Stable Phase Change Materials With GO- and Al2O3-Enhanced Ionic Liquid Nanofluids

To overcome the intrinsic limitations of polymer-based phase change gels, including low thermal conductivity, supercooling, and insufficient mechanical robustness, self-healing hydrogel-based form-stable phase change materials (FPCMs) were designed by in situ polymerization of graphene oxide (GO)- or aluminum oxide (Al 2 O 3 )-enhanced 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim][BF 4 ]) nanofluids within a dynamic poly(N-isopropylacrylamide-co-UPyMA) network. The incorporation of quadruple hydrogen-bonding UPy motifs endowed the polymer network with intrinsic self-healing capability and mechanical adaptability. Uniformly dispersed GO and Al 2 O 3 nanofillers significantly enhanced heat transport and crystallization behavior. At optimized loadings, the nanofluids exhibited markedly suppressed supercooling, and the phase transition temperature of the FPCMs could be effectively tuned by adjusting ionic liquid content, with melting point shifts exceeding 5°C. GO-based FPCMs completely eliminated supercooling, while Al 2 O 3 -based systems achieved an over 85% reduction. High latent heat values above 230 J/g were retained, together with thermal conductivity enhancements exceeding 140% compared to the neat ionic liquid. Benefiting from the dynamic polymer network, the FPCMs showed excellent self-healing performance, with strength recovery exceeding 80% and good durability upon repeated damage–healing cycles. This work highlights a polymer network engineering strategy for constructing multifunctional FPCMs with tunable thermal behavior, efficient crystallization regulation, and mechanical resilience for thermal energy storage applications.