Adsorption of finite polymers in different thermodynamic ensembles

TL;DR

This paper explores how finite polymer chains adsorb onto surfaces using advanced simulations, revealing unique thermodynamic behaviors during the transition, especially for short chains with strong attraction.

Contribution

It provides a detailed microcanonical analysis of the adsorption transition in finite polymers, highlighting the convexity of entropy and its implications for phase transition understanding.

Findings

Convex microcanonical entropy indicates a first-order-like transition.

Strong surface attraction leads to distinct conformational phases.

Finite size effects significantly influence the adsorption behavior.

Abstract

We investigate the cooperative effects of a single finite chain of monomers near an attractive substrate by first constructing a conformational pseudo-phase diagram based on the thermal fluctuations of energetic and structural quantities. Then, the adsorption transition is analyzed in more detail. This is conveniently done by a microcanonical analysis of densities of states obtained by extensive multicanonical Monte Carlo simulations. For short chains and strong surface attraction, the microcanonical entropy turns out to be a convex function of energy in the transition regime. This is a characteristic physical effect and deserves a careful consideration in analyses of cooperative macrostate transitions in finite systems.