Nonlinear mechanics of thermoreversibly associating dendrimer glasses

The integration of thermoreversibly associating groups into polymers produces a wide variety of complex behavior arising from the finite lifetime of the ``sticky,'' thermoreversible bonds. Using hybrid molecular dynamics / Monte Carlo simulations, we characterize the nonlinear mechanical properties of associating trivalent dendrimer network glasses with a focus on their energy dissipation properties. Various combinations of sticky bond (SB) strength and kinetics are employed. The toughness (work to fracture) of these systems displays a surprising deformation-protocol dependence; different association parameters optimize different properties. In particular, ``strong, slow'' SBs optimize strength, while ``weak, fast'' SBs optimize ductility via self-healing during deformation. We relate these observations to breaking, reformation, and partner switching of SBs during deformation. These studies point the way to creating associating-polymer glasses with tailorable mechanical properties.