Coarse-grained molecular dynamics modeling of reaction-induced phase separation

Abstract

We develop a model to describe reaction-induced phase separation in thermoplastic-toughened thermoset polymers at molecular scales. To achieve the temporal and spatial scales required for phase separation we use coarse-grained molecular dynamics where beads represent bi-functional epoxy, a di-amine crosslinker and monomers in the thermoplastic. The model describes the curing of the thermoset using a distance criterion to identify chemical reactions on the fly during a molecular dynamics simulation. We characterize how composition, curing temperature and conversion degree affect the onset of phase separation and domain growth. The onset of phase separation in terms of degree of cure depends on cure temperature and the subsequent growth of domain size during cure can be described with two power laws. Interestingly, the domain size vs. time following quenching after cure also follows power-law behavior but with exponent of approximately ¼, lower than those observed in simple binary mixtures and linear chain polymers.