Post-polymerization modification and release of functional groups based on an NIR light-emitting organoboron π-conjugated polymer

Abstract

We developed a near-infrared (NIR) light-emitting organoboron π-conjugated polymer that can be functionalized through post-polymerization modification with click chemistry. The perpendicularly protruding substituents at the boron center are reactive and almost electronically independent from the polymer main chain. These properties allow the quantitative chemical modification of functional groups as side-chains even after polymerization, without any influence on the main-chain properties. In particular, to the best of our knowledge, we first demonstrate that the boron-fused azobenzene complex can release the introduced functional units at the boron center upon treatment with reactive agents, such as nucleophilic bases and photo-radical initiators. We observed that the release of pyrene side-chains can be monitored by the disappearance and appearance of the NIR and blue emissions, respectively, even for water-dispersible polymer nanoparticles. This study provides a novel design strategy for stimuli-responsive theranostic systems based on NIR-fluorescent π-conjugated polymers.