Synthesis of photocleavable linear macromonomers by ATRP and star macromonomers by a tandem ATRP-click reaction: Precursors to photodegradable model networks

Atom transfer radical polymerization (ATRP) and the copper-catalyzed azide - alkyne cycloaddition (CuAAC) were utilized for the synthesis of photodegradable polymeric materials by two complementary schemes. Linear azido-telechelic macromonomers possessing a photocleavable functionality at the center were synthesized by ATRP and subsequent end-group modification. These macromonomers were cross-linked with a tetrafunctional alkyne by CuAAC to form insoluble materials which degraded upon exposure to UV light of 350 nm to yield soluble star polymer products of defined molecular weight. Complementary to this approach, four-armed star polymers possessing photocleavable arms and terminal azides were prepared by a novel one-pot CuAAC/ATRP reaction followed by end-group modification. These star polymers were cross-linked with a linear, bifunctional alkyne to yield insoluble materials which, upon exposure to UV light, degraded to yield linear polymers of defined molecular weight.