Correspondence between the rigid amorphous fraction and nanoconfinement effects on glass formation

Semicrystalline polymers' properties are strongly influenced by the presence of a rigid amorphous fraction (RAF) of material with enhanced glass transition temperature and suppressed mobility. Here, we review striking similarities between this domain and near-interface regions of altered dynamics in other nanostructured polymers, including thin films, nanocomposites, layered films, and ionomers. Building on these observations, we present results of molecular simulations of model nanolayered polymers in which one layer is crystalline. The results of these simulations, which bear close similarities to semicrystalline homopolymers while providing a well-defined equilibrium crystal size, suggest that the RAF shares the same phenomenology and mechanism as dynamic interphases in these other polymeric systems. Specifically, the fraction of rigid amorphous material is driven by the scale of cooperative rearrangements characteristic of dynamics in polymers and other supercooled liquids. These results situate the RAF as a specific instance of a general tendency towards broad dynamic interphases in polymers and other glass-forming materials. (c) 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 907-918