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.