A comprehensive molecular dynamics study of a single polystyrene chain in a good solvent

In this study, molecular characteristics of polystyrene (PS) was calculated measuring its dilute-solution properties in toluene at 288.15 K via molecular dynamics (MD) simulations. The solution models consisted of PS chains with different number of repeating units all of which were in a dilute regime. In order to investigate the compatibility between the polymer and the solvent molecules, interaction energy and Flory-Huggins (FH) interaction parameter were estimated. The simulation results indicate that increasing the chain repeating units enhanced the interaction between the solute and the solvent. Additionally, the chain dimensions were evaluated calculating the radius of gyration (R_g) and end-to-end distance, r0. To determine the dynamic behavior of the chains in the solutions, mean square displacement (MSD) and diffusivity coefficient were calculated. The simulation results indicated that the chain rigidity at low molecular weight and chain flexibility with increasing the molecular weight influenced chains dynamic behavior and diffusivity. Moreover, radial distribution function (RDF) illustrated the effect of steric hindrance of the chains in dilute solution on capturing the solvent molecules. In addition, solution viscosity was calculated by performing non-equilibrium molecular dynamics simulation (NEMD). The obtained results of chain characteristics and viscosity showed a good agreement with experimental results published previously. This agreement confirms the accuracy of the applied simulation method to characterize the dilute solutions and the chains characteristics.