Synthesis and study of poly(3-hexylthiophenes) and poly(3-dodecylthiophenes) containing halogen and sulfur substituents in theω-position of the side chain

Abstract

Poly[3-(6-bromohexyl)thiophene] (1) and poly[3-(12-bromododecyl)thiophene] (2) were synthesized by chemical polymerization of their respective monomers, 3 and 4, using FeCl3. NMR spectroscopy showed 81% of head-to-tail couplings and GPC showed M̄n = 51,500 and 91,100 with PDIs of 5.2 and 1.7 for 1 and 2, respectively. Conductivities of the I2- and FeCl 3-doped 1 were 18 and 7.5 S cm-1 and for 2 were 32 and 46 S cm-1, respectively. Poly[3-(6-iodohexyl)thiophene] (8) was prepared by SN2 displacement (>97%), using NaI, on 1. Poly[6-(3-thienyl)- 1-hexyl S-thioacetate] (10a) and poly[12-(3-thienyl)-1-dodecyl S-thioacetate] (10b) were prepared from 1 by post-polymerization SN2 reactions. They were insoluble in organic solvents and had 13C CP-MAS NMR spectra consistent with the structures. Reaction of 1 with thiourea followed by basic hydrolysis gave poly[3-(6-mercaptohexyl)thiophene] (11). This thiol functionalized polymer was also insoluble in common organic solvents and it, too, had a 13C CP-MAS NMR spectrum consistent with the structure. Polymers 10a and 11 showed pressed pellet conductivities of 4 × 10 -5 and 2.3 × 10-2 S cm-1 when doped with FeCl3, respectively and 8 × 10-5 and 0.44 S cm -1 when doped with I2, respectively. TGA of polymers 1, 8 and 11 showed thermal decomposition in two stages.