Concentration and Size Dependence of Dielectric Strength and Dielectric Relaxation of Polymers in Solutions of a ϑ Solvent via Molecular Dynamics Simulations

We consider the dielectric strength and dielectric relaxation of dilute and semidilute solutions of polymers in a ϑ solvent. A molecular dynamics technique is employed and the simulation results are contrasted with dielectric spectroscopy measurements, providing an insight into the molecular factors that affect the experimental behavior. The relation between the dielectric strength and the end-to-end distance of the chains, used in experiments to determine polymer dimensions, is established via equilibrium and nonequilibrium simulations. The dielectric loss spectra are computed from the end-to-end vector autocorrelation function of the simulated systems. At infinite dilution the simulation spectra conform well with the Rouse model prediction. The spectra broaden with increasing concentration, and a normal-mode analysis suggests that the overlapping of the chains leads to a broader distribution of relaxation times. Finally, normal mode relaxation times are found to be exponential in density.