Local free energy landscapes of photoisomerization in polymer matrices Gustavo Perez Lemus 2 , Timothy Sirk 1 , Juan J. de Pablo 1 1 Polymers Branch, US Army Research Laboratory, USA, 2 The University of Chicago, USA Photoactive molecules have emerged as promising tools for inducing mechanical and optical responses in soft materials. Despite the great potential of these molecules, previous computational studies have largely focused on their behavior in vacuum or solution systems, leaving their behavior in more complex environments, such as polymer networks, largely unexplored. Recently, molecular dynamics simulations have been used to study the behavior of azobenzene molecules in polymer network glasses, revealing the importance of the local molecular interactions in determining the wait-time for photoisomerization. Building on this work, we present here enhanced sampling simulations of photoactivated azobenzene molecules (AB) dispersed in a polymer network. Our simulations show that the local polymer environment of AB molecules plays a critical role in modulating the photoisomerization free energy landscape, resulting in a heterogeneous dynamics that explains the previously observed distribution of wait times. These results provide a deeper understanding of the behavior of photoactive molecules in complex environments, and offer new opportunities for designing soft materials with tailored mechanical and optical properties. References 1. Salerno, K. M., Lenhart, J. L., de Pablo, J., & Sirk, T. W. (2023). Photoisomerization and local stability in molecular and polymer-network glasses. Molecular Systems Design & Engineering, 8(1), 105-114. 2. Fiorin, G., Klein, M. L., & Hénin, J. (2013). Using collective variables to drive molecular dynamics simulations. Molecular Physics, 111(22-23), 3345-3362. 3. Thompson, Aidan P., H. Metin Aktulga, Richard Berger, Dan S. Bolintineanu, W. Michael Brown, Paul S. Crozier, Pieter J. in't Veld et al. "LAMMPS-a flexible simulation tool for particle-based materials modeling at the atomic, meso, and continuum scales." Computer Physics Communications 271 (2022): 108171.
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