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 Al 2 O 3 particles in the polysiloxane matrix. Their influence on the surface modification of Al 2 O 3 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 Al 2 O 3 surface, and the silicone paste prepared by filling 70.8 vol% mixed-size Al 2 O 3 particles had the lowest viscosity. When the branched-chain siloxane oligomer was used, the filling load of the modified Al 2 O 3 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 Al 2 O 3 particles and the branched-chain siloxane oligomer as the fluidity modifier for silicone paste.