Adhesion and mechanical properties of poly(dimethylsiloxane) bottlebrush elastomers

Poly(dimethylsiloxane) (PDMS) bottlebrush elastomers (BBEs) are attractive soft materials with well-controlled bulk mechanical properties. However, their surface and interfacial properties have not been studied in depth. We report a detailed study of the adhesion of PDMS BBEs to glass using a contact adhesion test to determine the critical energy release rates, G_c, as a function of interfacial separation velocity. For BBEs, G_c for initiating separation, G₀, was found to be independent of the crosslink density. We hypothesize that the monomer chemistry of side chains plays a primary role in defining surface properties for this materials system. After crack initiation, BBEs showed a significantly lower G_c and less velocity dependence than linear chain networks. Scaling analysis attributes these properties to the faster dissipative relaxation mechanisms within the BBEs. These findings demonstrate that the adhesion properties of BBEs can be finely tuned through the monomer chemistry and side chain length for potential applications.