Monte Carlo Study of the Phase Structure of Compact Polymer Chains

TL;DR

This study investigates the phase transitions of single homopolymer chains using advanced simulation techniques, revealing weak size dependence and no divergence in specific heat, with implications for understanding polymer phase behavior.

Contribution

It introduces a detailed Monte Carlo analysis of homopolymer phase transitions, comparing uniform and non-uniform sequences with advanced sampling methods.

Findings

Weak size dependence of specific heat peak

No divergence of specific heat observed

Comparison between uniform and non-uniform sequences

Abstract

We study the phase behavior of single homopolymers in a simple hydrophobic/hydrophilic off-lattice model with sequence independent local interactions. The specific heat is, not unexpectedly, found to exhibit a pronounced peak well below the collapse temperature, signalling a possible low-temperature phase transition. The system size dependence at this maximum is investigated both with and without the local interactions, using chains with up to 50 monomers. The size dependence is found to be weak. The specific heat itself seems not to diverge. The homopolymer results are compared with those for two non-uniform sequences. Our calculations are performed using the methods of simulated and parallel tempering. The performances of these algorithms are discussed, based on careful tests for a small system.