Polyimide-based azobenzene polymer networks have demonstrated superior photomechanical performance
over more conventional azobenzene-doped pendent and cross-linked polyacrylate networks. These materials
exhibit larger yield stress and glass transition temperatures and thus provide robustness for active control of
adaptive structures directly with polarized, visible light. Here we develop a constitutive modeling framework and
experimentally quantify both the photomechanical and theromechanical coupling in these materials. Whereas
photochemical reactions clearly lead to deformation, as indicated by a rotation of a linear polarized light source,
temperature and viscoelasticity can also influence deformation and complicate interpretation of the photostrictive
constitutive behavior. The rate dependent deformation induced by these two effects is quantified experimentally
through photomechanical stress measurements and infrared camera measurements. The results are compared to
a model that includes both rate dependent deformation as a function of the optically active azobenzene molecules,
coupling to the polymer network viscoelasticity, and thermal expansion. Bayesian statistics is utilized to elucidate
the differences in thermomechanical and photomechanical deformation and the influence of viscoelasticity on light
induced shape memory effects.
William Oates, Sadiyah S. Chowdhury, Matthew Worden, and Dennice Roberts, "Rate dependent modeling, experimental validation, and uncertainty quantification of photostrictive polymers," Proc. SPIE 10165, Behavior and Mechanics of Multifunctional Materials and Composites 2017, 1016515 (Presented at SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring: March 28, 2017; Published: 11 April 2017); https://doi.org/10.1117/12.2263676.
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