Polymers synthesized from (3-alkylthio)thiophenes by the FeCl₃ oxidation method

Thiophenes substituted by alkylthio (hexylthio and dodecylthio) pedant groups were polymerized using the FeCl₃ oxidation method. The polymers were characterized using microanalyses, conductivity measurements, thermogravimetry (TG) and ¹H NMR, UV-Vis, FTIR and XPS. The polymers are regiorandom in structure as expected and have a head-to-tail (HT) content of about 80% based on the ¹H NMR spectrum. Poly[(3-hexylthio)thiophenes] (PHTT), which carries the shorter side chain, exhibits a higher solubility in common organic solvents and is more thermally stable than the polymers with the longer dodecylthio poly[(3-dodecylthio)thiophenes] (PDDTT) chains. The polymers are moderately conductive after being doped by FeCl₃ or I₂. The high concentration of covalently bonded chlorine found from XPS and microanalysis and supported by ¹H NMR spectra suggests chlorination of the backbone occurred during the polymerization process. The influence of chlorination on the absorption spectra and conductivity were noted and discussed.