Multiscale modeling of glass transition in polymeric films: Application to stereoregular poly(methyl methacrylate)s

The multiscale modeling scheme has been extended to derive the coarse-grained potentials for simulating glass transition temperatures (T-g) of the bulks and the freely-standing films of two stereoregular poly (methyl methacrylate) (PMMA) configurations. The extensive molecular dynamics simulations reasonably reproduce the volumetric properties. Furthermore, the dynamical T-g sensibly exhibits the Flory-Fox relation with molecular-weight or film-thickness, which is not revealed by the volumetric T-g. Thus, for either of the PMMA bulks, the experimental T-g and the simulated (dynamical) T-g values obey a linear scaling relation, which is used to infer the actual T-g of the film. Consequently, syndiotactic PMMA films show greater T-g depressions from the bulks than the isotactic PMMA films at the same thicknesses, which is in good agreements with the experimental observations. Such a computational framework holds a bright promise to quantitatively predict T-g values and related properties of various confined polymer systems. (C) 2018 Elsevier Ltd. All rights reserved.