Main-chain photoresponsive polymers with controlled location of light-cleavable units: from synthetic strategies to structural engineering

Photoresponsive polymers have gained more and more attention in recent years since light stimulation can be spatiotemporally localized and controlled. In general, photoresponsive polymer structures are classified into two categories: one is for polymers in which the chromophores are positioned in the side-chain as pendants; while the other one covers polymers whose photoresponsive species are catenated onto the chain backbone. Since there are a number of reviews dealing with the first category, we turn our sight to focus on the main-chain photodegradable polymers, highlighting the recent progress and the rapidly expanding spectrum of well-defined light-sensitive architectures. On the basis of the variety of synthetic strategies for incorporating the photosensitive functionalities into the polymer chain, one could rationally design and construct main-chain photodegradable polymers with diverse macromolecular structures and functions. Finally, we suggest the possible future directions and perspective in this area.