Static Rouse Modes and Related Quantities: Corrections to Chain Ideality in Polymer Melts

TL;DR

This paper challenges the traditional view that polymer chains in melts behave like ideal phantom chains by showing significant deviations in Rouse mode correlations due to excluded volume effects, supported by simulations and theory.

Contribution

It provides the first detailed analysis of Rouse mode correlations in polymer melts, demonstrating the importance of non-ideal effects neglected in mean-field models.

Findings

Simulations show deviations from phantom chain predictions for non-zero excluded volume.

Perturbation theory accurately describes the observed correlations.

Results highlight the need to consider non-mean-field effects in polymer melt models.

Abstract

Following the Flory ideality hypothesis intrachain and interchain excluded volume interactions are supposed to compensate each other in dense polymer systems. Multi-chain effects should thus be neglected and polymer conformations may be understood from simple phantom chain models. Here we provide evidence against this phantom chain, mean-field picture. We analyze numerically and theoretically the static correlation function of the Rouse modes. Our numerical results are obtained from computer simulations of two coarse-grained polymer models for which the strength of the monomer repulsion can be varied, from full excluded volume (`hard monomers') to no excluded volume (`phantom chains'). For nonvanishing excluded volume we find the simulated correlation function of the Rouse modes to deviate markedly from the predictions of phantom chain models. This demonstrates that there are nonnegligible correlations along the chains in a melt. These correlations can be taken into account by perturbation theory. Our simulation results are in good agreement with these new theoretical predictions.