Dynamics of photoresponsive molecules in glassy solids

The photoresponse of azobenzene and azobenzene-like molecules undergoing the trans → cis photoisomerization transition has been primarily explored through simulation and experiment in solution or vacuum. The response and behavior of these photoactive molecules in solids, where barriers to rearrangement are significantly higher, is less well characterized. Here we use molecular dynamics simulations to study the behavior of azobenzene and disperse red one during and after photoactivation in glassy samples. Data show that the dynamics of photoactivated molecules and the surrounding solid depends little on the sample temperature or measures of local stability such as density and energy. On the other hand, the height of transition barriers, which depends strongly on intermolecular interactions, cooling rate and temperature, is reflected in the waiting time between photoactivation and a local transition. The timescale for flipping is compared with the timescale for rotational and diffusive motion. The rotation of azobenzene or disperse red one around the long axis of the molecule is correlated with the wait time or barrier to flipping while the translational motion and the rotation of the long-axis itself is less correlated with the flipping wait time.