Rouse mode analysis of chain relaxation in reversibly crosslinked polymer melts

Abstract

Polymer melts with chains undergoing reversible crosslinking have distinctively favorable dynamic properties, e.g., self-healing and reprocessability. In these situations, there are two relevant elementary time scales: the segmental and the sticker association times. A convenient framework to model these situations is the sticky Rouse model and here we perform hybrid molecular dynamics (MD)–Monte Carlo (MC) simulations to examine its relevance. In agreement with the underpinning idea discussed above, we find that reversibly crosslinked chains show two distinct modes of relaxation behavior depending on the magnitude of bond lifetimes. For bond lifetimes shorter than the chain end-to-end relaxation time, the polymers exhibit essentially Rouse-like dynamics, but with an apparently increased local friction relative to the non-sticky analog. For longer bond lifetimes, the chains exhibit two modes of relaxation: the faster mode is independent of the bond lifetime, but the slower mode is controlled by it. However, these slower mode results are not consistent with the predictions of the sticky Rouse model. Our Rouse mode analysis as a function of chain length, N, implies that this is likely a result of the relatively short N's employed, but it nevertheless suggests that theories need to include these short chain effects if they are to be relevant to experimental systems with short chains following Rouse dynamics.