Theory and Monte Carlo simulations for the stretching of flexible and semi-flexible single polymer chains under external fields

TL;DR

This paper develops a universal physical framework for understanding the non-uniform stretching of single polymers under external fields, providing analytical models and Monte Carlo simulations for flexible and semi-flexible chains.

Contribution

It introduces a unified approach to analyze non-uniform polymer stretching under external fields, deriving analytical results for different models and validating them with simulations.

Findings

Analytical results for freely-jointed and worm-like chain models.

Monte Carlo simulations confirm theoretical predictions.

Characterization of polymer conformation and fluctuations under various conditions.

Abstract

Recent developments of microscopic mechanical experiments allow the manipulation of individual polymer molecules in two main ways: \textit{uniform} stretching by external forces and \textit{non-uniform} stretching by external fields. Many results can be thereby obtained for specific kinds of polymers and specific geometries. In this work we describe the non-uniform stretching of a single, non-branched polymer molecule by an external field (e.g. fluid in uniform motion, or uniform electric field) by a universal physical framework which leads to general conclusions on different types of polymers. We derive analytical results both for the freely-jointed chain and the worm-like chain models based on classical statistical mechanics. Moreover, we provide a Monte Carlo numerical analysis of the mechanical properties of flexible and semi-flexible polymers anchored at one end. The simulations confirm the analytical achievements, and moreover allow to study the situations where the theory can not provide explicit and useful results. In all cases we evaluate the average conformation of the polymer and its fluctuation statistics as a function of the chain length, bending rigidity and field strength.