Engineering the Hybrid Interfaces in Ladder-Like Polysilsesquioxane/Al2O3 Manocomposites for Enhancing Thermal Conductivity

The potential of ladder-like polysilsesquioxanes (LPSQs) combined with thermally conductive fillers for developing nanocomposites (NCs) with enhanced thermal conductivity (TC) has recently gained interest. While early studies emphasize the importance of controlling ladder-filler interactions, the role of the hybrid interface on interfacial thermal resistance and TC remains underexplored. To address this gap, novel photocurable NCs were developed by incorporating Al2O3 nanoparticles (NPs) functionalized with methacrylate (MA) or amino (AA) groups into LPSQs bearing methacrylate and phenyl side chains. Characterizations revealed that methacrylate conversion and crosslinking significantly affect TC. Furthermore, the nature of covalent and non-covalent interactions at the ladder-filler interface influences both LPSQs structural organization and NCs thermal behavior. Among unfilled matrices, methacrylate-rich polysilsesquioxane (LPMASQ) displays the highest TC due to effective crosslinking. MAPSQ(46), with a 40/60 methacrylate-to-phenyl ratio, shows slightly lower TC, where reduced polymerization was offset by it-it stacking that promotes heat transfer. The introduction of MA NPs improves TC in all systems, particularly in LPMASQ, where copolymerization with the matrix reduces interfacial thermal resistance. Conversely, AA NPs, with lower dispersibility and weaker interactions, affect chain organization in LPMASQ, introducing phonon scattering and lowering TC. However, in mixed LPSQs like MAPSQ(64), with a 60/40 methacrylate-to-phenyl ratio, amino groups enhance thermal diffusivity, suggesting that weak interactions can be beneficial in matrices with limited polymerization. These results underscore the critical role of tuning both LPSQs side chain composition and NPs surface functionalization to balance interfacial interactions and maximize thermal performance in polymer NCs for advanced thermal management applications.