Synthesis and properties of a soluble polythiophene derivative with a urethane side chain

A solution processible thiophene polymer with a hydrogen-bond-forming urethane group in the side chain, viz., poly[2-(3-thienyl)ethanol n-butoxycarbonylmethylurethane] (PURET), has been synthesized. The polymer is soluble in a wide variety of solvents such as chloroform, dimethylsulfoxide, N-methylpyrrolidone, and trifluoroacetic acid among others. Optical quality thick films are obtained by solution casting. The presence of extensive hydrogen bonding is established with the help of temperature-dependent infrared spectroscopy. NMR spectroscopic study indicates the presence of about 33% regio-isomeric defects in the polymer. The polymer forms yellow-colored solutions (lambda(max) = 430 nm) in most of the organic solvents, while in trifluoroacetic acid the polymer is oxidized and exhibits an additional band with an absorption maximum at around 780 nm. The conductivity of the polymer is in the order of 1 S/cm.