A Closer Look at the Light Induced Changes in the Visco-elastic Properties of Azobenze-Containing Polymers by Statistical Nanoindentation

TL;DR

This study investigates how light influences the visco-elastic properties of azobenzene-containing polymers, revealing significant changes in hardness and creep behavior under illumination using statistical nanoindentation.

Contribution

It provides detailed experimental insights into the light-induced visco-plastic behavior of azobenzene polymers, highlighting the effects on hardness and creep dynamics.

Findings

Light increases film hardness more than elastic stiffness.

Illumination induces visco-plastic behavior in the polymer.

Creep experiments show dissipative effects under polarized light.

Abstract

The mechanical properties of azobenzene-containing polymer films are statistically measured by instrumented nanoindentation experiment in the dark and under illumination in the absorption band of the azobenzene molecules, with special emphasis on the creep behavior and recoverability. We use Dispersed Red 1 azobenzene derivatives, which remain in the stable trans isomer state in the dark and form a dynamical photo-stationary state between cis and trans isomer under illumination. Light induces a higher change in the film hardness than in the elastic stiffness, revealing the occurrence of a visco-plastic behavior of the film under illumination. Creep experiments performed at a constant load show a striking dissipative effect linked to the mass flowing under polarized illumination.