Multistage Reversible T_g Photomodulation and Hardening of Hydrazone-Containing Polymers

The glass transition temperature (T_g) of a series of polyacrylate- and polymethacrylate-based polymers having bistable hydrazone photoswitches as pendants increases upon photoisomerization. The ensuing photohardening of the polymeric network was corroborated using nanoindentation measurements. The bistability of the switch allowed us to lock-in and sustain multiple T_g values in the same polymeric material as a function of the hydrazone switch's Z/E isomer ratio, even at elevated temperatures.