Visible Light-Mediated Photoclick Functionalization of a Conjugated Polymer Backbone

Efficient postpolymerization functionalization of conjugated polymer backbones is generally challenging. Here, we report the first example of a conjugated polymer backbone that can be functionalized using visible light. This polymer contains a 9,10-phenanthrenequinone moiety in the conjugated backbone, which reacts with electron-rich vinyl ethers via visible light-mediated photoclick chemistry. Synthesis of the 9,10-phenanthrenequinone dibromide monomer requires only a single step from commercially available precursors, and the corresponding polymer can be prepared by Suzuki polycondensation. The photoclick reaction was found to be extremely fast, requiring only a few minutes of irradiation using a commercially available aquarium light-emitting diode. It is also insensitive to air and moisture and requires no additional catalysts. The resulting photoclick conjugates were characterized using NMR, UV–vis, fluorescence, and IR spectroscopy. Photoclick coupling to polyethylene glycol vinyl ether produced a dramatic change in polymer solubility and emission properties, while maintaining an identical degree of polymerization and dispersity of the polymer backbone. We demonstrate the first instance of a photopatternable conjugated polymer backbone by incorporating the conjugated polymer into a silicone elastomer and functionalizing it in a spatially resolved manner.