Photodynamics of stress in clamped nematic elastomers

TL;DR

This paper models the complex, temperature-independent force dynamics in clamped nematic elastomers under illumination, revealing a universal behavior driven by nonlinear dye absorption and bleaching waves.

Contribution

It introduces a universal, parameter-free model that accurately describes the stress buildup dynamics in clamped nematic elastomers across temperatures.

Findings

Model fits experimental data without additional parameters

Dynamics are governed by nonlinear absorption and bleaching waves

Universal behavior observed across different temperatures

Abstract

We describe the complex time-dependence of the build up of force exerted by a clamped photo-elastomer under illumination. Nonlinear (non-Beer) absorption leads to a bleaching wave of a significant cis isomer dye concentration deeply penetrating the solid with a highly characteristic dynamics. We fit our experimental response at one temperature to obtain material parameters. Force-time data can be matched at all other temperatures with no fitting required -- our model provides a universal description of this unusual dynamics. The description is unambiguous since these are clamped systems where gross polymer motion is suppressed as a possible source of anomalous dynamics. Future experiments are suggested.