Molecular simulation via connectivity-altering Monte Carlo and scale-jumping methods: application to amorphous polystyrene

Well-equilibrated atactic-polystyrene (aPS) samples are obtained through the end-bridging Monte Carlo (EBMC) algorithm. A coarse-grained (CG) description of aPS is used; monomers are represented by two CG beads. The algorithm produces correct polymer conformations on all length scales, beyond the size of the CG beads. The code is very efficient, even though the acceptance of 0.001-0.005% is approximately 10-100 times lower than in the original EB code for PE. Systems of aPS of the order of 5000 monomers (50 chains of 100 monomers on average) can be equilibrated on all length scales within a week, in a single-processor run. The computer code is also adequate for simulations of other polymers that have the same regularity in their sequence of chemical groups and that are modeled at the same or at a coarser level of description

Structural properties of atactic polystyrene of different thermal history obtained from a multiscale simulation

A method is presented to obtain well-equilibrated atactic polystyrene (aPS) samples for molecular simulations. The method starts with equilibrating the polymer in the melt at length scales beyond the Kuhn length lK, using end-bridging Monte Carlo techniques; at this level a (2:1)-coarse-grained description of aPS is being employed. Subsequently atomistic detail is reintroduced, and the sample is equilibrated at the smallest length scales as well. At length scales beyond lK the simulated polymer chain conformations fulfill the random-coil hypothesis of Flory, and C8 = 8.7 ± 0.1 at 463 K. Eventually various glassy samples are created by subjecting the melt sample to different cooling rates. Pair correlations are in agreement with existing X-ray data, and the amount of dihedral angles in the trans (t) state agrees with NMR data. On the level of dyads, the conformations of racemic dyads agree well with existing NMR results. At the same time, meso dyads conformations do not agree: 65% of meso dyads is in the gt/tg state (NMR: 80%); 25% is in tt state (NMR

Simulation studies of soft matter: generic statistical properties and chemical details

61.43.Bn Structural modeling: serial-addition models, computer simulation, 83.10.Rs Computer simulation of molecular and particle dynamics,