Post-Polymerization Modification and Release of Functional Groups Based on a NIR Light-Emitting Organoboron π-Conjugated Polymer

Abstract

We develop the near-infrared (NIR) light-emitting organoboron π-conjugated polymer that can be functionalized through post-polymerization modification with click chemistry. The perpendicularly-protruded substituents at boron are reactive and almost electronically independent from the polymer main-chain. These characters allow 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 firstly demonstrate that the boron-fused azobenzene complex can release the introduced functional units on boron triggered by the treatments with reactive agents such as nucleophilic bases and radicals with photo-radical generators. We observed that the release of pyrene side-chains can be monitored by disappearance and appearance of the NIR and blue emissions, respectively, even with water-dispersible polymer nanoparticles. This study should provide a novel design strategy for stimuli-responsive theranostic systems based on NIR-fluorescent π-conjugated polymers.