Preparation of thermal interface materials with high thermal conductivity through the synergistic effect of Monoalkoxy-Terminated polysiloxane and branched siloxane oligomers

Four mono-alkoxysilyl-terminated asymmetric siloxane oligomers and a dimethylvinylsilyl-terminated branched-chain structure siloxane oligomer were prepared by a series of reactions to improve the filling loads and dispersion of Al2O3 particles in the polysiloxane matrix. Their influence on the surface modification of Al2O3 particles and the viscosity of composite materials was investigated. When the branched-chain siloxane oligomer was not used, mono-trimethoxysilyl-terminated asymmetric siloxane oligomers exhibited the best modification effect on the Al2O3 surface, and the silicone paste prepared by filling 70.8 vol% mixed-size Al2O3 particles had the lowest viscosity. When the branched-chain siloxane oligomer was used, the filling load of the modified Al2O3 particles could be further increased to 84.3 vol% under the synergistic effect of the mono-trimethoxysilyl-terminated asymmetric siloxane oligomers and the branched-chain siloxane oligomer. The viscosity of the silicone paste decreased with the increase in the polymerization degree of the dimethylsiloxane segment in the-mono trimethoxysilyl-terminated asymmetric siloxane oligomers. Meanwhile, the thermal conductivity of these silicone pastes also exhibited an increasing trend with the increase in the polymerization degree of the asymmetric siloxane oligomers. A thermal interface material with a thermal conductivity higher than 8.0 W/(m·K) was successfully prepared by using the asymmetric siloxane oligomers as the surface modification agent for Al2O3 particles and the branched-chain siloxane oligomer as the fluidity modifier for silicone paste.