Bottom-Up Multiscale Approach to Estimate Viscoelastic Propertiesof Entangled Polymer Melts with High Glass Transition Temperature

HY Liang and K Yoshimoto and P Gil and M Kitabata and U Yamamoto and JJ de Pablo, MACROMOLECULES, 55, 3159-3165 (2022).

DOI: 10.1021/acs.macromol.1c02044

A multiscale computational method is presented for the prediction of the viscoelastic properties of entangledhomopolymer melts with high glass transition temperatures. Starting from an atomistic model of a polymer, two coarserrepresentations are introduced???a coarse-grained model and a slip-spring representation???which successively operate at longer timeand length scales. The three models are unified by renormalizing the time and modulus scales, which is achieved through matchingtheir normalized chain mean squared displacement and stress relaxation modulus, respectively. To facilitate the relaxation ofentangled chains, the simulations are performed at temperatures higher than those accessible in experiments. Time-temperaturesuperposition is then applied to extrapolate the viscoelastic properties calculated at high temperatures to experimentally accessiblelower temperatures. This proposed approach can predict the linear rheology of the melt starting from an atomistic model and doesnot require experimental parameters as an input. Here, it is demonstrated for syndiotactic and atactic polystyrene, where goodagreement with experimental measurements is observed.

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