Statistical Mechanics of Aggregation and Crystallization for Semiflexible Polymers

TL;DR

This study uses multicanonical simulations to explore how semiflexible polymers aggregate and crystallize, revealing distinct phase behaviors and structural fluctuations similar to peptide formation.

Contribution

It provides new insights into the thermodynamics of semiflexible polymer aggregation, highlighting differences from related heteropolymer models and identifying phase separation characteristics.

Findings

Aggregation involves strong structural fluctuations.

Stiff semiflexible polymers form liquid-crystal-like phases.

Aggregation transition shows size-dependent surface effects.

Abstract

By means of multicanonical computer simulations, we investigate thermodynamic properties of the aggregation of interacting semiflexible polymers. We analyze a mesoscopic bead-stick model, where nonbonded monomers interact via Lennard-Jones forces. Aggregation turns out to be a process, in which the constituents experience strong structural fluctuations, similar to peptides in coupled folding-binding cluster formation processes. In contrast to a recently studied related proteinlike hydrophobic-polar heteropolymer model, aggregation and crystallization are separate processes for a homopolymer with the same small bending rigidity. Rather stiff semiflexible polymers form a liquid-crystal-like phase, as expected. In analogy to the heteropolymer study, we find that the first-order-like aggregation transition of the complexes is accompanied by strong system-size dependent hierarchical surface effects. In consequence, the polymer aggregation is a phase-separation process with entropy reduction.