Microwave-Assisted Polycondensation via Direct Arylation of 3,4-Ethylenedioxythiophene with 9,9-Dioctyl-2,7-dibromofluorene

Abstract

For synthesis of π-conjugated polymers, polycondensation via direct arylation reactions of C–H bonds in aromatic monomers with dibromo-arylenes has attracted increasing attention as a simple synthetic method in which the preparation of organometallic reagents is unnecessary. To develop direct arylation polycondensation for practical use in the synthesis of optoelectronic polymer materials, microwave-assisted reactions were investigated and optimized in terms of a kind of base, concentration, reaction time, and amount of catalyst. Under the optimized conditions, the microwave-assisted direct arylation of 3,4-ethylenedioxythiophene with dibromofluorene for 30 min with catalyst (1 mol %) gave the corresponding polymer with an extremely high molecular weight up to 147 000. The high molecular weight of the polymer enables formation of a large and flexible self-standing film, leading to an advantage in fabricating organic thin-film devices. The elemental analysis and MALDI-TOF-MS reveal that the polymer has high purity and no bromo- and metallo-terminals. Because only microwave-assisted direct arylation provided these features in the polymer, the present method is superior to conventional methods. Therefore, microwave-assisted polycondensation via direct arylation methodology lends itself well to practical application using inherent product from economical and environmental points of view for the synthesis of pure optoelectronic materials.