A multiscale simulation of amorphous polystyrene

A multiscale simulation method to investigate amorphous polymeric materials for vinyl polymer was applied for glassy polystyrene (PS) with different tacticity. PS chains were coarse-grained and then mapped onto the second nearest neighbor diamond (2nnd) lattice incorporating short- and long-range interactions from the modified rotational isomeric state (RIS) model and the discretized Lennard-Jones (LJ) potential function, respectively. Bulk PS structures composed of 14 chains with 42 monomer units was generated and equilibrated on lattice Monte Carlo (MC) simulation. The on-lattice properties including molecular size, conformational statistics and chain dynamics were compared. The chain mobility of neat PS melts with different stereochemistry are qualitatively ordered as: iPS < aPS << sPS. There is no clear correlation for these relative diffusions with molecular size and chain stiffness but can possibly be related to the intermolecular contribution i.e. chain packing among neighboring chains. Next, fully atomistic amorphous PS models at the bulk density were obtained by the reverse-mapping procedure to convert the coarse-grained chains to recover the missing atoms. After energy minimization, molecular and material properties including torsional angle distribution, solubility parameter, radial distribution function and neutron scattering intensity are determined and compared for amorphous PS structures.