Order-Disorder Transitions and Melting in a Helical Polymer Crystal: Molecular Dynamics Calculations of Poly(Ethylene Oxide)

TL;DR

This study uses molecular dynamics simulations to explore the structural transitions and melting process of crystalline poly(ethylene oxide), revealing a two-stage melting mechanism involving loss of order and chain helicity.

Contribution

First detailed atomistic simulation of PEO melting, identifying a two-stage transition with specific order parameter changes and dynamic behaviors.

Findings

Melting occurs in two stages: loss of interchain order and chain helicity.

Sliding diffusion and anisotropic reorientational dynamics are observed in the solid state.

Simulation results agree with 1H NMR experimental data.

Abstract

Structural transitions and the melting behavior of crystalline poly(ethylene oxide),(CH2-CH2-O)n, (PEO) has been investigated using fully atomistic, constant pressure-constant temperature (NPT) molecular dynamics (MD) simulations. Melting of PEO proceeds in two stages; Order parameters reveal the loss of interchain orientational correlations and of chain helicity in the first and second stages of melting respectively. Sliding diffusion and anisotropic reorientational dynamics of the polymer backbone are observed in the solid state, in agreement with 1H NMR experiments.