An Emerging Unified View of Dynamic Interphases in Polymers

The properties of nanostructured polymeric materials reflect the presence of a dynamic interphase in which polymer segmental dynamics, glass formation, mechanics, and transport properties are altered from their bulk states. Examples include nanoconfinement effects on polymer nanofilms, reinforcement effects in polymer nanocomposites and filled rubbers, formation of a rigid amorphous fraction in semicrystalline polymers, and observation of suppressed-mobility domains around ionic aggregates in ionomers. Whereas many of these phenomena have been viewed as emerging from system-specific mechanisms, here recent work is highlighted that contributes to an emerging unified understanding of the dynamic interphase in all of these systems. This view suggests that the size scales of dynamic interphases in polymers are generally determined by the scale of cooperative rearrangements intrinsic to relaxation dynamics in supercooled glass-forming liquids. It also implicates alterations in local segmental rattling as playing a central role in the dynamic interphase, and it suggests that near-interface modifications in dynamics exhibit a general dependence on the interfacial work of adhesion and the relative high-frequency moduli of the interface-adjacent domains.