Multiscale modeling of polystyrene under different environments in solution, as a melt or in polymer blends

The dynamics of atactic polystyrene in the neighborhood of cyclohexane and N, N-dimethylformamide are investigated by atomistic molecular dynamics simulations. We investigate the solvation process and its temperature and polymer concentration dependencies. The dynamics of both solvents and polymer chains are studied by correlation times and activation energies associated with the reorientation. Since some phenomena, e.g., entanglement and phase separation behavior, only happen on time scales not accessible by a fully atomistic simulation, it is highly desirable to have mesoscale models of polystyrene at longer chains and higher concentrations to understand the polymer dynamics. Mapping is the only option to derive a mesoscale model based on an atomistic simulation. A newly developed technique, the "Iterative Boltzmann Inversion" has been used to generate the non-bonded potential parameters in this work. For the first time, this technique has been applied to both a polystyrene melt and polyisoprene-polystyrene blends.; The statics and dynamics of polystyrene melts with chain length ranging from 15 up to 240 monomers have been investigated from the developed mesoscale model. It is the first time we quantify the entanglement length of this systematically coarse-grained melt. Our analysis concludes that the entanglement length of this mesoscale PS melt is about 85 monomers from various manifestations, particularly, mean squared displacements, reorientation of local vectors along the backbone, the Rouse plateau in the chain length dependence of the diffusion constant, and Rouse mode analysis. We also validate the crystallinity of PS with the mesoscale model and PS shows clearly crystallization tendencies with the decrease of the temperature.; Mapping to binary blends technically is more demanding than to a pure melt. The various potentials are strongly interdependent and the order of optimization influences the convergence speed. With the mesoscale polymer blend models, we are able to capture the phase separation behavior. The polymer blends embark on phase separation around 10 monomers. The separated phases are lamellar at equimolar concentration, cylindrical at unbalanced concentration or spherical at further unbalanced concentration. We depict the morphology diagram for various blend systems. We simulate the systems of both 2 and 4 times bigger and validate that the morphologies are independent of system size.