Coumarin-Caged Polyphosphazenes with a Visible-Light Driven On-Demand Degradation

Polymers that, upon photochemical activation with visible light, undergo rapid degradation to small molecules are described. Through functionalization of a polyphosphazene backbone with pendant coumarin groups sensitive to light, polymers which are stable in the dark could be prepared. Upon irradiation, cleavage of the coumarin moieties exposes carboxylic acid moieties along the polymer backbone. The subsequent macromolecular photoacid is found to catalyze the rapid hydrolytic degradation of the polyphosphazene backbone. Water-soluble and non-water-soluble polymers are reported, which due to their sensitivity toward light in the visible region could be significant as photocleavable materials in biological applications.