(83i) The Dynamics and Mechanics of Inhomogeneous Polymer Networks

Phase separated polymer networks can be synthesized from materials that can provide complimentary properties to the resulting gel, and as a result co-networks formed from glassy and rubbery polymers are emerging as candidates for applications that require both mechanical support and molecular mobility to allow transport. The mechanical and failure properties of these co-networks are only beginning to be studied, and given the nanoscale structure present in co-networks, there are likely to be strong heterogeneities in the properties on the molecular scale. In this talk, I will present our work using coarse-grained molecular dynamics simulations to characterize the dynamic mechanical properties of glassy/rubbery co-networks as a function of the molecular weight between crosslinks and the volume fraction of the glassy domain. We find strong gradients in the mobility near the interface of the microdomains that are homogenized as the strand length is decreased. By employing a model that allows for bond breaking, we can examine the microscopic mechanism for failure in these networks. We find that the fraction of bonds broken in the glassy domain tracks the overall composition of the network, and the onset of bond breaking is coincident with the stress in both domains becoming comparable to each other.