Simulations of Glass Transition and Mechanical Behavior of Off-Stoichiometric Crosslinked Polymers

This work explores the influence of blend composition,networkarchitecture, and hydrogen bonding on the material properties of crosslinkedepoxy networks, focusing on the glass transition temperature (T (g)) and Young's modulus (Y). We used coarse-grained molecular dynamics simulations to simulatevarying compositions of stiff and flexible components in epoxy monomerblends with varying excess of curative. We find that, without hydrogenbonding, networks of any composition show a monotonically increasing T (g) with decreasing excess curative, consistentwith theory. In contrast, we find that when hydrogen bonding is introduced,the binary blend networks show significant enhancement in T (g) for lightly crosslinked systems. This resultcontributes to an explanation of the anomalous T (g) behavior observed experimentally in these systems. We furtherfind that Y is generally enhanced by hydrogen bonds,especially below T (g), demonstrating thathydrogen bonding has a significant influence on mechanical propertiesand can allow access to other desirable dynamic behavior, especiallyself-healing.

Automated summary

This work investigates the influence of blend composition, network architecture, and hydrogen bonding on the material properties of crosslinked epoxy networks. The study finds that the introduction of hydrogen bonding significantly enhances the glass transition temperature (T(g)) of binary blend networks with lightly crosslinked systems. It also demonstrates that hydrogen bonding generally enhances Young's modulus (Y) and allows access to desirable dynamic behavior such as self-healing.