Separation strain rate dependence on the failure of polymer adhesion with mobile promoters

Comprehensive molecular dynamics simulations, employing a coarse-grained bead-spring model, are conducted to study the failure of adhesion between two immiscible polymers stitched together via mobile promoters. A realistic model under separating tension is constructed that enables both chain pulling out viscously and bulk dissipation in two dissimilar glassy polymers that one is dense melt and another is loose. The contributions to the adhesion energy from thermodynamics and chain suction are studied for dependence of the strain rate at fixed basic molecular parameters. With low density of connectors, either adhesion toughness or strength changes slightly with separation strain rate as viscous loss is negligible. But rate effects become evident for long connectors with high density, viscoelastic sliding friction and reptation of chains dominate and the fracture energy increases with strain rate. The results provide insights into the evolution of adhesion surfaces coupled with promoter molecular slipping out of bulk melts, which are useful for future developments of continuum models for failure of polymeric interfaces.