Short-range order and collective dynamics of poly(vinyl acetate): A combined study by neutron scattering and molecular dynamics simulations

The structure and collective dynamics at local length scales of poly(vinyl acetate) (PVAc) have been investigated by combining neutron scattering on a deuterated sample and fully atomistic molecular dynamics simulations. The experimental data have provided microscopic information at molecular level and a critical check to validate the simulated cell. In order to gain deep insight on the structure factor, we have grouped the simulation results in terms of three molecular substructures: the main chain, the carboxyl group, and the methyl group. The study of the resulting static partial structure functions has revealed the origin of the diffraction peaks, and a real-space evaluation of the characteristic radial distribution functions has allowed separating intra- and interchain contributions to the total correlation functions. The extension of this study to the dynamic structure factor has revealed a coupling between the side-group motions and the main-chain dynamics at intermolecular distances. Moreover, a decrease in coherency of the main-chain motions at intermolecular level is observed with increasing temperature, leading to a rather decoupled behavior between the main chains at 200 K above the glass transition.