Breakdown of the Kratky-Porod Wormlike Chain Model for Semiflexible Polymers in Two Dimensions

TL;DR

This study uses large-scale simulations to show that the Kratky-Porod model fails to accurately describe semiflexible polymers in two dimensions, especially beyond very short contour lengths, due to a crossover to self-avoiding walk behavior.

Contribution

It demonstrates the breakdown of the Kratky-Porod model for 2D semiflexible polymers, revealing the absence of the Gaussian regime and implications for experimental interpretations.

Findings

Kratky-Porod model only valid for very short polymers in 2D

Semiflexible polymers exhibit a crossover from rod-like to self-avoiding walk behavior

Gaussian regime is absent in 2D for these polymers

Abstract

By large-scale Monte Carlo simulations of semiflexible polymers in $d=2$ dimensions the applicability of the Kratky-Porod model is tested. This model is widely used as "standard model" for describing conformations and force versus extension curves of stiff polymers. It is shown that semiflexible polymers in $d=2$ show a crossover from hard rods to self-avoiding walks, the intermediate Gaussian regime (implied by the Kratky-Porod model) is completely absent. Hence the latter can also describe force versus extension curves only if the contour length is only a few times larger than the persistence length. Consequences for experiments on biopolymers at interfaces are briefly discussed.