Preparation of a soluble and neutral alkyl derivative of poly(3,4-ethylene-dioxythiophene) and its optical properties

Soluble and non-doped poly(3,4-ethylenedioxythiophene) with a hexyl substituent (PEDOTh-C6 (Ni)), was first synthesized by Ni promoted dehalogenation polycondensation of the corresponding monomer. PEDOTh-C6 (Ni) exhibited good solubility in common organic solvents such as CHCl3, CH2Cl2, and DMF, in contrast to poor solubility of the corresponding polymer synthesized by oxidative polymerization. GPC analysis indicated that PEDOTh-C6 (Ni) had Mn and Mw of 5400 and 8500 (vs polystyrene standards); 1H NMR analysis gave an Mn value of 11,000. A cast film of PEDOTh-C6 (Ni) received electrochemical p-doping at 0.20 V vs Ag+/Ag. Chemical and electrochemical oxidation of PEDOTh-C6 (Ni) led to appearance of new absorption bands in the near infrared region.