CHARACTERIZATION, PROPERTIES AND DOPING OF POLY(3-ALKYLTHIOPHENE-2,5-DIYL)S, P3RTHS (R=N-C6H13,N-C8H17,N-C12H25), PREPARED BY USING ZERO-VALENT NICKEL-COMPLEX

Poly(3-alkylthiophene-2,5-diyl)s, P3RThs (alkyl = hexyl (P3HTh), octyl (P3OTh) and dodecyl (P3DTh)), have been prepared from the corresponding 2,5-dihalo-3-alkylthiophenes by means of an organometallic technique using zero-valent nickel complex as the dehalogenating reagent. Polymers are obtained in high yield with high molecular weight (M(w) congruent-to 190 000 for P3HTh as determined by the light scattering method) and contain a larger proportion of head-to-head units than head-to-tail units. Electrochemical doping and undoping of the polymers proceeds with good reversibility. Chemically doped polymers with oxidizing reagents such as I2 and FeCl3 and electrochemically doped polymers exhibit similar electrical conductivity (sigma) (e.g. 4 +/- 1 x 10(-1) S cm-1 for P3HTh). However, stability of the sigma value with time differs, the sigma values of I2- and FeCl3-doped polymers being virtually unvaried after 40 days under Ar, whereas the sigma values of the electrochemically doped polymers show rather steep decrease with time.