Role of Nanoscale Heterogeneity in the Mechanical Performance of Hybrid Elastomers

Silicone-organic interpenetrating polymer networks(IPNs)are hybrid materials with enhanced mechanical properties relativeto pure silicones. Here, we compare structure-property relationshipsof graft-IPNs of polydimethylsiloxane (PDMS) made with methyl methacrylate(MMA) and isobornyl methacrylate (IBoMA). We found evidence for increasedpolymer-polymer mixing in the PDMS/PIBoMA graft-IPNs, whichwas impacted by the higher relative compatibility of these two polymerscompared to PDMS/PMMA. These PDMS/PIBoMA hybrid materials possessedfracture toughness values up to 400x greater than unreinforcedPDMS elastomers, contrasted by the lower toughness values and highlyphase separated morphologies of the PDMS/PMMA hybrids. Increased temperaturereduced the fracture and fatigue resistance of the hybrids as nanoscalemechanical heterogeneity was lost between PDMS and the methacrylatepolymers, which is consistent with the behavior of existent siliconeresin-filled silicone materials.