Alternating block copolymers incorporating 3-alkyl-substituted thiophene and aniline repeat units: novel electrically conductive and fluorescent polymers

A series of alternating block copolymers incorporating 3-alkyl-substituted thiophene and aniline repeat units (PATBAs): poly{4-[2-(3-methyl)thienyl]benzenamine} (PMTBA), poly{4-[2-(3-butyl)thienyl]benzenamine} (PBTBA), poly{4-[2-(3-octyl)thienyl]benzenamine} (POTBA) and poly{4-[2-(3-dodecyl)thienyl]benzenamine} (PDTBA) were synthesized via chemical oxidative polymerization using ferric chloride as oxidant. The resulting polymers were characterized by FT-IR, UV-Vis, fluorescence spectroscopy, elemental analysis, thermogravimetry and electrical conductivity measurements. It was shown that coupling during polymerization occurred through the α-position of the thienylene ring and the amino moiety. Upon doping with iodine the polymers attained electrical conductivity ranging from 10−4 to over 10−3 S cm−1. The fluorescence quantum efficiency of the polymers in solution was found to decrease with increasing pendant alkyl-chain length. Scanning electron microscopy (SEM) revealed a globular morphology similar to poly[4-(2-thienyl)benzenamine] and polythiophene.