Abstract
ABSTRACTMolecular dynamics computer simulations are used to study the structure and dynamics of 1nm wide films of poly(ethylene oxide)(PEO) confined between mica type layered silicates of different cation exchange capacities(CEC). The simulation setup mimics the experimental systems formed by intercalation of PEO in silicate clays with differing numbers of inherent charges. Counterbalancing lithium cations are present in the interlayer gallery to offset the negative charge on the silicate platelets created by the isomorphic substitution of trivalent aluminum by divalent magnesium ions. It is seen that the presence of the lithium has a significance influence on the behavior of the system, with PEO segmental motion strongly dependent on the number of Li+ present in the slit pore. In particular, the coexistence of fast and slow modes for C-H bond dynamics is heavily affected due to the strong interaction between the Li+ ions and partially charged PEO oxygen. In conjunction with local density inhomogeneities, the coordination between lithium and oxygen is responsible for the anomalous segmental dynamics of nanoconfined PEO.
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