Utilizing Self-Immolative ATRP Initiators to Prepare Stimuli-Responsive Polymeric Films from Nonresponsive Polymers

Stimuli-responsive polymers were synthesized by atom transfer radical polymerization (ATRP) using a photoresponsive self-immolative bifunctional initiator. The photoactivated self-immolative junctions allow transforming nonresponsive polymers into photocleavable polymers that can be split into two equally sized fragments when exposed to the stimulation. We demonstrate this modular approach by preparing a series of photoresponsive poly(benzyl methacrylate) and polystyrene polymers of various molecular weights. Taking advantage of the well-defined architecture of the polymers, we studied their photoresponse as thin films and examined the effect of irradiation time and solvent addition on the degree of response and splitting. The results show that the polymers can be split in the solid phase, confirming that the self-immolative quinone methide elimination can occur in solid phase. Importantly, we could also obtain insights into the role of the mobility of the polymer chains in the solid phase and in the presence of solvent molecules on the responsiveness of the films and degree of splitting. The potential to introduce such modular self-immolative units into different types of widely used of polymers will allow the utilization of this approach to create wide range of responsive materials that can undergo vast structural changes by relatively minor synthetic modifications.