Aggregation-Induced Emission and Photocyclization of Poly(hexaphenyl-1,3-butadiene)s Synthesized from "1 + 2" Polycoupling of Internal Alkynes and Arylboronic Acids

A new polymerization method for in situ generation of luminescent polymers with aggregation-induced emission characteristics from readily prepared or commercially available reactants was developed in this work. The "1 + 2" polycoupling of internal alkynes and arylboronic acids took place under mild reaction conditions and was tolerant to moisture, air, and monomer stoichiometric imbalance, furnishing poly(hexaphenyl-1,3-butadiene)s (PHBs) with partially or wholly conjugated structures in satisfactory yields. All the PHBs showed good solubility, thermal stability, and film-forming ability. Their optical properties could be easily tuned by proper monomer design and external perturbation. The PHBs underwent active photocyclization in both solution and solid states, converting them to poly(dihydronaphthalene)s. Such a property made them promising materials for fabricating luminescent photopatterns. A new mechanistic pathway was proposed as supplementary to explain the aggregation-induced emission (AIE) phenomenon by studying the emission of PHBs and the corresponding model compound.