Preparation and Properties of 2,7-Linked N-Alkyl-9H-carbazole Main-Chain Polymers

Preparation of poly(9-alkyl-9 H -carbazole)-2,7-diyls using palladium-catalyzed cross-coupling reactions involving 2-bromo-7-bromomagnesio-9-alkyl-9 H -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 °C. 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.