Development of hybrid inorganic/organic nanocomposites with enhanced thermal conductivity

Effective thermal management is a critical challenge across technologies such as microelectronics, automotive, and aerospace systems. In advanced electronics, continual miniaturization and rising power density intensify local heat generation; if heat is not removed and redistributed efficiently, overheating can degrade performance, reliability, and device lifetime. Thermal management materials (TMMs) are therefore engineered to extract heat from active junctions, spread it over larger areas, and couple it into engineered coolers. Practical TMMs for electronics must combine high thermal conductivity (TC) with low interfacial thermal resistance while meeting electrical, mechanical, and manufacturing constraints, most notably electrical insulation, thermal stability, some degree of mechanical compliance, and compatibility with scalable processing. A widely adopted route to achieve these competing requirements is to develop polymer-based nanocomposites (NCs), where high thermally conductive ceramic fillers form heat conduction pathways within an otherwise thermally insulating polymer matrix. In this context, this thesis explores ladder-like polysilsesquioxanes (LPSQs) as organosilicon building blocks that can be integrated into polymer matrices to tailor structure, dynamics and interfacial interactions. Although LPSQs have been employed in diverse systems, their targeted use as TMMs, and the exploitation of their tunable chemistry to regulate interfacial thermal resistance, remain comparatively underdeveloped. The purpose of this work is to establish chemistry–structure–property guidelines for maximizing thermal transport in electrically insulating polymer nanocomposites by balancing covalent and non-covalent interactions at the hybrid polymer-filler interface. LPSQs were synthesized via sol–gel chemistry and processed into films by solvent casting followed by ultraviolet-induced (UV-induced) curing; likewise, LPSQ/Al2O3 NCs were prepared by embedding variable loadings of functionalized γ-Al2O3 nanoparticles within the ladder matrices. To elucidate the role of interfacial interactions, LPSQs were synthesized bearing different organic pendant groups, and Al2O3 nanoparticles were functionalized using distinct silane coupling agents to systematically tune the polymer–filler interphase. Network formation and interfacial chemistry were investigated using Fourier transform infrared spectroscopy (FTIR), solid-state nuclear magnetic resonance (ss-NMR), and X-ray diffraction (XRD); morphology and filler dispersion were assessed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDXS). Thermal stability was evaluated by thermogravimetric analysis (TGA), while TC was determined from density, specific heat capacity, and thermal diffusivity values of the samples. The results demonstrate that processing and chemistry must be co-optimized: UV-curing conditions govern crosslink density and network topology, which in turn influence packing, defect formation, and the development of heat-transfer pathways. Modulating the LPSQ side chain chemistry highlights a key trade-off between network formation and interchain interactions, with certain formulations producing more compact, structurally integrated domains that favor heat transport. Most importantly, this thesis establishes that maximizing TC in highly filled LPSQ/Al2O3 nanocomposites requires matching nanoparticle surface functionality to the dominant interaction mechanism of the matrix. These insights were then transferred to polybutadiene-based systems (PB), yielding PB/LPSQ/Al2O3 nanocomposites as proof-of-concept, electrically insulating, thermally conductive films, where LPSQs act as a filler carrier and interfacial mediator phase. The materials underwent thermal stability, structural, morphological, and mechanical evaluations via TGA, DSC, SEM, EDXS, FTIR, ss-NMR, and DMA (dynamic mechanical analysis), and TC was evaluated by direct heat flow assessment. The most effective formulations depended on aligning matrix chemistry with nanoparticle functionalization. Promising performance as TMM was thus achieved using a limited amount of ceramic fillers, thereby preserving the mechanical behavior of the elastomer. Overall, this thesis provides a molecularly grounded framework linking LPSQ design, interchain interactions, and polymer–filler interfaces to thermal transport in flexible nanocomposites, paving the way for rational development of next-generation TMMs. Future work can build on these guidelines by expanding interfacial chemistries, refining domain architecture in flexible matrices, and translating these concepts into scalable manufacturing routes for electronics packaging.