Light-induced release of molecules from polymers

The release of molecules from polymers upon light stimulus has been investigated for a range of applications in particular for drug delivery. In this review, the concept of light-induced release processes from polymers is summarized. Light-triggered processes can be divided into two approaches, the light induced degradation of polymers and the light-induced polarity change of the polymers. Functional groups that can enable the breakdown of the polymer or the cleavage of a linker between polymer and small molecule encompass coumarine and o-nitrobenzyl groups while azobenze and spyropyrane undergo reversible changes. Although the literature is dominated by these four compound classes, functional groups such as anthracene, pyrene, perylene, 2-diazo-1,2-naphthoquinone, and BODIPY can undergo similar changes. Degradation of polymers or simple polarity changes can trigger the release of small molecules such as drugs, but also gas molecules such as nitric oxide and macromolecules including DNA and proteins can be liberated upon light-trigger.