Free-energy barrier to melting of single-chain polymer crystallite

TL;DR

This study uses Monte Carlo simulations to investigate the melting behavior of single-polymer crystallites, revealing superheating, surface disorder, and a significant free-energy barrier to melting.

Contribution

It provides the first detailed analysis of the free-energy barrier and superheating phenomena in single-polymer crystallite melting.

Findings

Superheating of crystallites above melting temperature

Disordered surface layer increases with superheating

Sudden order-disorder transition with a large free-energy barrier

Abstract

We report Monte Carlo simulations of the melting of a single-polymer crystallite. We find that, unlike most atomic and molecular crystals, such crystallites can be heated appreciably above their melting temperature before they transform to the disordered "coil" state. The surface of the superheated crystallite is found to be disordered. The thickness of the disordered layer increases with superheating. However, the order-disorder transition is not gradual but sudden. Free-energy calculations reveal the presence of a large free-energy barrier to melting.