Aza-Michael Chemistry for PDMS-Based Covalent Adaptable Elastomers: Design and Dual Role of the Silica Filler

In this study, polydimethylsiloxane (PDMS)-based covalent adaptable networks have been prepared in a one-pot, catalyst-free way in which dynamic β-amino esters (BAEs) are introduced via aza-Michael addition between available acrylate/amine-terminated PDMS-compounds. The straightforward introduction of those BAE-groups in such high-value elastomers provides the ability to relax the applied stress at elevated temperatures and hence the capability of reshaping the networks by compression molding at least 5 times without significant changes in properties. Moreover, the mechanical and dynamic properties are tunable by varying the cross-linker and/or filler content. Interestingly, the utilization of silica fillers not only enhances the network formation and mechanical properties but also accelerates the exchange reactions, resulting in twice faster stress relaxation at elevated temperatures while maintaining creep resistance at service temperatures.