Role of Nanoscale Heterogeneity in the Mechanical Performance of Hybrid Elastomers

Silicone–organic interpenetrating polymer networks (IPNs) are hybrid materials with enhanced mechanical properties relative to pure silicones. Here, we compare structure–property relationships of graft-IPNs of polydimethylsiloxane (PDMS) made with methyl methacrylate (MMA) and isobornyl methacrylate (IBoMA). We found evidence for increased polymer–polymer mixing in the PDMS/PIBoMA graft-IPNs, which was impacted by the higher relative compatibility of these two polymers compared to PDMS/PMMA. These PDMS/PIBoMA hybrid materials possessed fracture toughness values up to 400× greater than unreinforced PDMS elastomers, contrasted by the lower toughness values and highly phase separated morphologies of the PDMS/PMMA hybrids. Increased temperature reduced the fracture and fatigue resistance of the hybrids as nanoscale mechanical heterogeneity was lost between PDMS and the methacrylate polymers, which is consistent with the behavior of existent silicone resin-filled silicone materials.