Silica is widely used as a filler in cross-linked silicones to improve material properties, particularly mechanical strength. This reinforcement effect is generally attributed to the high modulus of silica particles and hydrogen bonding between silica and PDMS chains. We report that Stober silica particles actively participate in the chemical cross-linking of linear PDMS prepared by anionic ring-opening polymerization of octamethylcyclotetrasiloxane (D4). The silica particles serve as Q reservoirs for the growing siloxane network and crosslinks are equilibrated into the matrix during polymerization. Scanning electron microscopy  and a series of swelling tests demonstrate the erosion of silica particles and the presence of covalent bonds between silica and PDMS. The living (self healing and chemical stress relaxing) nature of these materials will be reported as well as their use in preparing controlled modulus and gradient modulus materials.

Silica can be an active participant in silicone synthesis

246th National Meeting (2013)

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