Synthesis of conducting polymers

Abstract

A series of novel electronic conducting polymers has been prepared as potential low band gap materials. Stille coupling reactions were employed for the polymerization of 2,7-dibromospiro[4'.4'-dioctyl-2',6'-dioxocyclohexane]-r,9- fluorene (2-9) with l,4-bis(trimethylstannyl)benzene (2-20), 2,5-bis(trimethylstannyl)- furan (2-28) and 2,5-bis(trimethylstannyl)thiophene (2-5) to yield precursor polymers poly(2,7-spiro[4',4'-dioctyl-2',6'-dioxocyclohexane]-r,9-fIuorene-co-l,4-benzene) (PFKB), poly(2,7-spiro[4',4'- dioctyl-2',6'-dioxocyclohexane]-1 ',9-fluorene-co-2,5- furan) (PFKF) and poly(2,7-spiro[4'.4'-dioctyl-2',6'-dioxocyclohexane]-r,9- nuorene-co-2,5-thiophene) (PFKT). The precursor polymers have been converted to target fluorenone-based polymers by deacetylisation of the acetal substituents to the ketones. Model compounds have been synthesized as compounds 2-15 and 2-16. Compound 2-15 was converted to 2-16 to explore the method for conversion of the precursor polymers. The fluorenone-thiophene copolymer, PFT, gave the lowest band gap as ca. 1.6 eV. The known ionic conducting polymers poly[2,2'-(4,4'-oxydiphenylene)-5,5'- bibenzimidazole] (PBI-1), poly[2,2'-(4.4'-sulfonyldiphenylene)-5,5'-bibenzimidazole] (PBI-2), poly[2,2'-(4.4'-oxydiphenylene)sulfonyl-5,5'-bibenzimidazole] (PBI-3) have been synthesized. PBI-1 was cast as a thin film and doped with phosphoric acid. The ionic conductivity was 2.06 x 10⁻² s cm⁻¹ at 80°C.