Mechanical unfolding of a homopolymer globule: applied force vs applied deformation

TL;DR

This paper develops a mean-field theory to describe how a homopolymer globule unfolds under force, showing it unfolds suddenly without intermediates, with thresholds depending on solvent quality and polymer length.

Contribution

It introduces a quantitative mean-field model for globule unfolding under force, highlighting the absence of intermediate states and the dependence on solvent and polymer parameters.

Findings

Globule unfolds as a whole without intermediates.

Threshold force increases with poorer solvent and longer chains.

Unfolding behavior differs from fixed-distance ensemble.

Abstract

We propose the quantitative mean-field theory of mechanical unfolding of a globule formed by long flexible homopolymer chain collapsed in poor solvent and subjected to an extensional force We show that with an increase in the applied force the globule unfolds as a whole without formation of an intermediate state. The value of the threshold force and the corresponding jump in the distance between chain ends increase with a deterioration of the solvent quality and / or with an increase in the degree of polymerization. This way of globule unfolding is compared with that in the D-ensemble, when the distance between chain ends is imposed.