Effect of the surface functionalization on alumina-based fillers for enhancing the thermal conductivity of polymeric nanocomposites

One of the main relevant limitations of the use of polymer-based materials in modern technological applications (e.g., electronics and optoelectronics, photonics, automotive) is their intrinsic low thermal conductivity that does not allow polymers to counteract the occurrence of the thermal degradation due to the in-service overheating phenomenon. To overcome this thermal constraint, polymer-based materials containing highly thermally conductive fillers are receiving great attention as they show an improved heat dissipation ability. However, recent studies report that a significant improvement of thermal conductivity in polymeric nanocomposites can be achieved only at high filler loadings, but this negatively affects both the mechanical behavior and density of the materials. Moreover, to achieve an efficient heat management, a continuous network of thermally conductive fillers crossing the entire composite is mandatory. 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. Hence, the present contribution reports on the recent results obtained by introducing different types of alumina-based hybrid fillers decorated at the surface with either metacrylate silane or octa-methacryl-POSS units at low filler loadings in a polybutadiene polymer matrix. Even if displaying a modest intrinsic thermal conductivity, alumina can represent a valid and appealing thermally conductive filler, due to its low cost, stable chemical performance and negligible toxicity. The promising results obtained for these hybrid ceramic fillers foreshadow their potential application in large-scale formulations.