In situ Photo-rheology Monitors Viscoelastic Changes in Photo-responsive Polymer Networks.

In situ photo-rheology is a powerful technique for characterizing the evolution of photo-responsive materials during irradiation. This technique enables time-resolved analysis of the mechanical properties of materials undergoing photo-induced molecular changes, such as during additive manufacturing, photo-polymerization, or photo-stimulation. We present a rheological method to monitor dynamic network formation by photo-responsive star polymers. This article describes procedures to configure a rheometer for simultaneous measurement and irradiation, prepare and load photo-responsive polymer samples, identify appropriate measurement parameters, and analyze time-resolved viscoelasticity. Mechanical and kinetic information provides insight into the dynamics of photo-responsive polymer networks. The goal of this protocol is to provide an example of experimental parameter selection, in situ photo-rheological measurements, and mechanical analysis of photo-responsive materials undergoing irradiation. Additionally, this protocol identifies potential modifications to customize the setup for many possible photo-responsive systems, thereby providing guidelines for future users across the materials science community. In situ photo-rheology improves the understanding of photo-responsive material properties, which is important for engineering materials with predictable processing by additive manufacturing, tunable mechanical performance, and stimuli-responsive functions.