Characterization of fractional viscoelastic relaxation behavior of a photopolymer film

Abstract

Photoresponsive polymers are commonly used for applications such as controlled drug delivery, patterned thin films of hydrogels and polymer brushes, photodegradable materials, and liquid crystal actuators.1 Photoresponsive polymers are unique as they can change shape when exposed to a certain wavelength, intensity, or polarization of light while not requiring an electrical circuit or tethered power supply. However, the majority of photoresponsive polymers are based on the azobenzene moiety and the conversion of light into mechanical work is often inefficient. This work summarizes the relaxation behavior of a novel photopolymer film derived from stilbene and its unsensitized analog. Experiments are conducted quantifying the relaxation behavior of the films. The relaxation behavior of the photopolymer is analyzed by comparing fractional order and integer order Maxwell models. All results are statistically validated using Bayesian uncertainty methods to obtain posterior densities for the model parameters. It is shown that the fractional order Maxwell model is superior based on errors that are an order of magnitude lower than the integer order Maxwell model.