Visible Light-Mediated Photoclick Functionalization of a Conjugated Polymer Backbone

Abstract

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 lightemitting 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.

Synthesis of Photoreactive Poly(ethylene oxide)s for Surface Modification

“…While AzPEG(3) was completely removed from the surface with water, small amounts of AzPEG(9) remained on the surface after washing with water (Figure S8). Therefore, AzPEG (9) and AzPEG (14) were next washed using solvents that dissolve AzPEG well, such as methanol and acetone. As a result, the FT-IR peak associated with the azide group was completely absent after washing the AzPEG(9)-treated surface with methanol (Figure S8).…”

A Survey of Strain‐Promoted Azide–Alkyne Cycloaddition in Polymer Chemistry

“…We recentlyr eportedaphenanthrenequinone-containing conjugated polymer that could undergo catalyst-free photoclick functionalization with vinyl ethers under ambient conditions. [30] This work demonstrated the first example of spatially resolved conjugated polymer backbonefunctionalization using light.…”

“…These transformations require some combination of elevated temperature, prolonged reaction time, or catalyst to achieve quantitative functionalization. We recently reported a phenanthrenequinone‐containing conjugated polymer that could undergo catalyst‐free photoclick functionalization with vinyl ethers under ambient conditions [30] . This work demonstrated the first example of spatially resolved conjugated polymer backbone functionalization using light.…”

“…[6,18,19] However,t race copper contamination of the product resultsi nc ytotoxicity that precludes biological applications, which has spurred as earch for copper-free click chemistry. [20] While there have been several click chemistry advances,i ncluding Staudinger ligation, [21][22][23] oxime or hydrazide ligation, [24,25] Pictet-Spengler ligation, [26] inverse-electron demand Diels-Alderc ycloaddition, [27] tetrazole 1,3-cycloaddition, [28] and vinyl etherphenanthrenequinonec oupling, [29,30] there are trade-offs between fast reaction kinetics, precursor benchtops tability,a nd synthetic ease. Though discovered by Wittig and Krebs nearly 60 years ago, [31] the facile reaction between as trained cyclooctyne and an azide was popularized by Bertozzi andc o-workers in 2004.…”

Shining a Light on Bioorthogonal Photochemistry for Polymer Science

“…A biologically useful demonstration of the power of this approach was the modification of the hydrophobic PQ backbone with vinyl ether modified polyethylene glycol, creating a uniquely water soluble conjugated polymer. [ 172 ] Determination of the reaction rates for PQ photochemistry and the ability to modify the chemistry to be activated with longer wavelength NIR light will determine its potential as a truly bioorthogonal photoclick reaction.…”