Barbier Hyperbranching Polymerization-Induced Emission from an AB-Type Monomer

Luminescent polymer materials have gained considerable research efforts in the past decades and are generally molecular designed by extending the π system of the polymer main chain or by incorporating chromophores into the polymer chain, which suffer from poor solubility, difficult synthesis, or multi-step procedures. Meanwhile, according to the step-growth polymerization theory, synthesis of hyperbranched polymers from an AB-type monomer is still challenging. Herein, we report a one-pot synthesis of nonconjugated luminescent hyperbranched polymer material via Barbier hyperbranching polymerization-induced emission (PIE) from an AB-type monomer. The key step in the realization of the hyperbranched polymer is bi-functionalization of a mono-functional group. Through a Barbier reaction between an organohalide and an ester group in one pot, bi-functionalization of mono-functional ester is realized through two-step nucleophilic additions, resulting in hyperbranched polytriphenylmethanols (HPTPM). Attributed to through-space conjugation and inter- and intramolecular charge-transfer effects induced by polymer chain, nonconjugated HPTPMs are PIEgens, which are tunable by monomer structure and polymerization time. When all phenyl groups are rotatable, HPTPM is aggregation-induced emission type PIEgen. Whereas, it is aggregation-caused quenching type PIEgen if some phenyl groups are rotation forbidden. Further potential applications of PIEgen are in the fields of explosive detection and artificial light harvesting systems. This work, therefore, expands the monomer library and molecular design library of hyperbranched polymers through "bi-functionalization of mono-functional group" strategy, which eventually expands the preparation library of nonconjugated luminescent polymer materials through one-pot PIE from nonemissive monomer.