Synthesis and Properties of Cationic Polyelectrolyte with Regioregular Polyalkylthiophene Backbone and Ionic-Liquid Like Side Groups

High-regioregular poly{3-[6-(1-methylimidazolium-3-yl)hexyl]thiophene-2,5-diyl bromide}, PMHT-Br, has been prepared by reaction of high-regioregular (above 92%) poly[3-(6-bromohexyl)thiophene-2,5-diyl] with 1-methylimidazole. PMHT-Br is soluble in water and water miscible solvents such as methanol, DMSO and shows solvatochromism; lambda(max) (nm): 423 (H2O); 435 (MeOH); 452 (DMSO). Increased absorption band broadening observed for aqueous solution as well as NMR spectra in 020 suggests a micelle-like structure of PMHT-Br molecules in these solutions: poly(3-hexylthiophene) core and 1-methylimidazolium bromide shell. Despite the disturbing effect of ionic groups, the solid-state PMHT-Br shows absorption maximum at 520 nm, the band edge at 660 nm (ca. 1.9 eV), and fluorescence emission with maximum at 635 nm, in a good agreement with the polymer regioregularity. Fluorescence emission maxima: lambda(em) (nm): 598 (H2O); 562 (MeOH); 574 (DMSO), occur in a vicinity of corresponding adsorption band edges. Plot of electrical conductivity of PMHT-Br (measured under the dynamic vacuum conditions, 5 x 10(-5) Pa) versus 1/Tshows a break at about 70 degrees C same as the temperature dependence of lambda(max) of the solid PMHT-Br. These breaks indicate an increase in the mobility of polymer segments and ions within PMHT-Br; however, a thermal analysis did not provide solid evidence for it. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3073-3081, 2010