Glass Transition Behavior of Crosslinked Epoxy/Amine Resins with Prospective Self-Healability

Self-healing polymers that can dynamically heal damage with no external intervention have enhanced longevity and reduced environmental impact.  One strategy to create self-healing polymers is to modify commodity polymers into highly branched networks, taking advantage of strong, glassy cores at the heart of the networks, while retaining mobility at free ends on the periphery of the networks.  Adding supramolecular interactions such as hydrogen bonding to those mobile free ends could enable self-healability across a wounded interface.  Using large scale coarse-grained molecular dynamics simulations, we calculate the thermomechanical properties of highly branched polymers with hydrogen-bonding end groups.  Our model is based on an epoxy system with amine crosslinkers. We vary the ratio of epoxy to amine and the ratio of two different epoxies (one stiff, one flexible), and determine the resulting polymer network architecture and glass transition behavior.  We find that experimentally observed anomalies in T_g are reproducible in-silico and explore the molecular basis for these anomalies.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.