A type of silicones strengthened by vinylethylene carbonate functional polyorganosilsesquioxane and crosslinked by primary ammonia and cyclic carbonate reaction: Experimental and MD simulation studies

Abstract

It's always a challenge to crosslink different polysiloxane oligomers through a common organic reaction to obtain high performance silicone materials. This paper reported a new type of silicone rubber (VPSR) that α,ω-aminopropyl polydimethylsiloxane (A-PDMS) was reinforced with vinyl carbonate functional polyhedral oligomeric silsesquioxane (VEC-POSS) and crosslinked by primary ammonia and cyclic carbonate reaction. VEC-POSS was synthesized from γ-mercaptopropyl polyhedral oligomeric silsesquioxane (SH-POSS) and vinyl carbonate (VEC) via the common thiol-ene click reaction. The silicones with high thermal stability, hydrophobicity and good tensile properties was obtained. FTIR confirmed the crosslinked network was formed by the combination of non-covalent bond and covalent bond. The enhancement effect of VEC-POSS was systematically studied by the experimental and molecular dynamics (MD) simulation. The results revealed that the increase of VEC-POSS contents enhanced the tensile strength and the contact angle to 3.35 MPa and 122.7°, respectively. The glass transition temperature (Tg) and the number of hydrogen bonds (H-bonds) increased with the increase of VEC-POSS contents, while the mean square displacement (MSD) and the free volume fraction (FFV) decreased gradually. Moreover, compared with the experimental results, the simulated Tg was consistent with the experimental Tan δ values, which proved the rationality of the model.