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.