Non-entropic theory of rubber elasticity: flexible chains grafted on a rigid surface

TL;DR

This paper proposes a non-entropic theoretical framework for rubber elasticity, replacing the end-to-end distribution with average energy, leading to better agreement with experimental data for grafted flexible chains.

Contribution

It introduces a modified model of rubber elasticity based on average energy, improving the description of grafted chain mechanics over traditional entropic theories.

Findings

The new model aligns well with uniaxial compression experiments.

Numerical simulations match observed mechanical behavior.

A micro-mechanism for reduced friction at rigid walls is proposed.

Abstract

The elastic response is studied of a single flexible chain grafted on a rigid plane and an ensemble of non-interacting tethered chains. It is demonstrated that the entropic theory of rubber elasticity leads to conclusions that disagree with experimental data. A modification of the conventional approach is proposed, where the end-to-end distribution function (treated as the governing parameter) is replaced by the average energy of a chain. It is revealed that this refinement ensures an adequate description of the mechanical behavior of flexible chains. Results of numerical simulation are compared with observations on uniaxial compression of a layer of grafted chains, and an acceptable agreement is shown between the model predictions and the experimental data. Based on the analysis of combined compression and shear, a novel micro-mechanism is proposed for the reduction of friction of polymer melts at rigid walls.