Synthesis of multifunctional block copolymers and their applications to organic electroluminescent devices with pseudo-layered structures

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The purpose of this project is to synthesize the complete monolithic polymers for efficient electroluminescent devices, where utilized polymers show ability to self-assemble to create pseudo-layered structures. In 2004, rod-coil type block copolymers consisting of fluorescent rod part with fluorinated alkyl chains, and hole transporting polymethacrylate with carbazole moiety were synthesized. It is confirmed that the solution coating of resulting copolymers led to surface segregated films where the air-to-polymer interface was predominately covered with low surface tension fluorinated rods. In 2005, graft copolymers based on polythiophene with charge transporting polymers branches were designed. Polythiophenes are generally highly fluorescent in a solution state, but severe quenching occurs in a film state, which limits the utilization of polythiophene in electroluminescent devices. In graft polymers, high density of branch chain prevents the aggregation of polythiophene backbones, keeping the conformation as in the solution. The graft copolymers were successfully synthesized with a combination of oxidative coupling polymerization and atom tranfer radical polymerization. As expected, the films of graft copolymers showed fluorescent natures like the solution. Living radical polymerization using ethylbenzene-TEMPO as an initiator and styrene derivatives with hole and electron transporting moiety as monomers afforded block copolymers.