Alumina-based fillers functionalized with polyhedral silsesquioxane units for enhancing the thermal conductivity of polymeric nanocomposites

Overheating represents one of the major causes of the in-service degradation of polymeric formulations, as this class of materials possess an intrinsic low thermal conductivity that limits their employment in several modern applications, ranging from (opto)electronics, photonics, to the tire industry. In order to face this critical issue, several efforts have been dedicated to the design of thermally conductive polymeric nanocomposites, mainly by introducing highly thermally conductive fillers into polymeric matrices. However, this apparently simple approach hides a huge complexity, which is the necessity of forming a continuous network of thermally conductive fillers crossing the entire composite to achieve an efficient heat transfer. In this context, interfacial phenomena play a major role as they favor the homogeneous distribution of the conductive fillers within the polymer matrix. In a previous study, it has been already verified that the surface functionalization of inorganic fillers (i.e., silica) with Polyhedral Oligosilsesquioxane (POSS) units, a family of hybrid inorganic-organic systems composed of an inorganic core of cage-like silicon oxide and several organic functional groups, significantly improved the dispersion and compatibilization of the inorganic fillers in the polymer matrix. Recently, we successfully demonstrated the potentiality in terms of heat transport and mechanical reinforcement of introducing a hybrid filler made by spherical γ-alumina nanoparticles decorated with POSS units at low filler loadings in a polybutadiene polymer.4 Here, we extend the investigation by considering the development of a hybrid filler made by anisotropic α-alumina nanorods decorated with POSS units.