Preparation of reactive nano-silica/polydimethylsiloxane composites with multiple crosslinked network structure and investigation of their mechanical properties

In this paper, a series of reactive nano-silica (denoted as RNS)/polydimethylsiloxane (denoted as PDMS) composites with multiple crosslinked network structure was fabricated by the combination of in-situ polymerization and physical blending route. Briefly, the PDMS molecular chains were grafted on the surface of RNS via chemical bonds during the in-situ polymerization to afford the RNS/PDMS composites with primary network consisting of surface-modified silica framework and surface-grafted PDMS chains. The as-obtained RNS/PDMS composites were further mixed with highly branched silica to afford the RNS/PDMS composites with secondary network formed upon filler-polymer interactions via hydrogen bonds. The as-obtained dual-network RNS/PDMS composites were finally vulcanized and cured in the presence of crosslinking agents and catalyst to construct the SiO2/PDMS elastomers with multiple crosslinked network structure. The microstructure and mechanical properties of the as-fabricated SiO2/PDMS elastomers were investigated in relation to their crosslink density and multiple crosslinked network structure. Findings reveal that the as-obtained SiO2/PDMS elastomers display higher tensile strength, tear strength, and elongation at break than the counterparts obtained by single in-situ polymerization route or physical blending route, which is attributed to the formation of multiple crosslinked network structure after curing.