Abstract
Abstract Affinities of poly(thienylene) type polymers toward electron acceptors (iodine and SO3) and electric conductivities of the polymer–electron acceptor adducts have been investigated. π-Conjugated poly(2,5-thienylene) has a high affinity toward iodine to absorb 60 wt% of iodine per the polymer. Poly(3-methyl-2,5-thienylene) has a higher affinity toward iodine and absorbs 136 wt% of iodine per the polymer. In the case of copolymer composed of 2,5- and 2,4-thienylene units the affinity against iodine increases with increase in the proportion of the 2,5-thienylene unit in the copolymer. The poly(2,5-thienylene)–iodine and poly(3-methyl-2,5-thienylene)–iodine adducts show electric conductivities of 5×10−2 S cm−1 and 4×10−1 S cm−1, respectively, at room temperature. The activation energies of the electric conduction are 10 kJ/mol and 7.6 kJ/mol for the poly(2,5-thienylene)–iodine adduct (wt% of iodine=60) and poly(3-methyl-2,5-thienylene)–iodine adduct (wt% of iodine=136), respectively. The electric conductivity of the copolymer–iodine adduct sharply decreases on introduction of the 2,4-thienylene unit into the copolymer. The electric conductivity of the iodine adduct of the copolymer containing only 6% of 2,4-thienylene unit drops to ca. 1/100 of that of the iodine adduct of pure poly(2,5-thienylene). The activation energy of the electric conduction of the polymer-iodine adducts decreases with increase in the content of the 2,5-thienylene unit as well as with the increase in the amount of iodine absorbed. Every poly(thienylene) type polymer has a high affinity toward SO3, a stronger electron acceptor than iodine, to absorb about 70 wt% of SO3 per the polymer. The SO3–polymer adducts have electric conductivities of ca. 10−4 S cm−1.
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