Synthesis, Self-Assembly, and Formation of Al3+ Complex Micelles for Diblock Copolymer of 2-((8-Hydroxyquinolin-5-yl)methoxy)ethyl Methacrylate and Styrene

Living/controlled polymerization of 2-((8-hydroxyquinolin-5-yl)methoxy)ethyl methacrylate (HQHEMA) was achieved by reversible addition-fragmentation chain transfer (RAFT) polymerization with 2-cyanoprop-2-yl dithiobenzoate (CPDB) as the RAFT agent and 2,2'-azoisobutyronitrile (AIBN) as the initiator in THF at 65 degrees C. The resulting PHQHEMA was used as a macro-RAFT agent in the RAFT polymerization of styrene to give diblock copolymer PHQHEMA-b-PS. The obtained diblock copolymer could self-assemble into nanosized micelles in a solvent mixture of toluene (Tol, selective solvent for block of polystyrene, nonsolvent for block of PHQHEMA) and THF (common solvent). The diameter and shape of the micelles were dependent on the molecular weights of the copolymers and the solvent compositions. The diameter of micelle increased with increasing molecular weight of the block copolymers and Tol content in the solvent mixture. Spherical micelles with a diameter in the range between 30 and 60 nm were formed under a Tol/THF ratio of 5:5 or 6:4, but, when the Tol/THF ratio increased to 8:2, the micelles changed from spherical structures to wormlike structures. Then, the formed micelles were used as nanoreactors to complex with triethylaluminum to give luminescent micelles with ionic cross-linking cores containing tris(8-hydroquinolinato)aluminum (Alq(3)). The luminescent micelles could be redispersed in the solvents of polystyrene after drying. The emission spectra showed that the Alq3 moieties acted as independent chromophores in the micelles.