Characterization, properties and doping of poly(3-alkylthiophene-2,5-diyl)s, P3RThs (R = n-C 6H 13, n-C 18H 17, n-C 12H 25), prepared by using zero-valent nickel complex

Abstract

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 ⋍ 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 I 2 and FeCl 3 and electrochemically doped polymers exhibit similar electrical conductivity (σ) (e.g. 4 ± 1 × 10 −1 S cm −1 for P3HTh). However, stability of the σ value with time differs, the σ values of I 2- and FeCl 3-doped polymers being virtually unvaried after 40 days under Ar, whereas the σ values of the electrochemically doped polymers show rather steep decrease with time.