Preparation and properties of 2,7-linked N-alkyl-9H-carbazole main-chain polymers

Preparation of poly(9-alkyl-9H-carbazole)-2,7-diyls using palladium-catalyzed cross-coupling reactions involving 2-bromo-7-bromomagnesio-9-alkyl-9H-carbazole derivatives is described. Monomers with a range of alkyl group substituents with different steric requirements were investigated, and their effects on the polymerization reaction were studied using gel-permeation chromatography. Polymers with different degrees of polymerization were obtained; dependent on the size and branching of alkyl group substituents on the carbazole repeat units. Structural analyses of the polymers revealed exclusive 2,7-linkage between consecutive carbazole repeat units on the polymer chains. The new polymers are thermally stable up to 450 degreesC. Electrochemical studies as well as absorption and fluorescence studies on the new polymers are presented together with a determination of their quantum yield of fluorescence in solution.