ELECTRICAL AND MECHANICAL-PROPERTIES OF ORIENTED POLY(3-ALKYLTHIOPHENES) .2. EFFECT OF SIDE-CHAIN LENGTH

The mechanical and electrical properties of solution-processed poly(3-alkylthiophenes) with alkyl side-chain lengths of 6, 8 and carbon atoms are discussed. Tensile drawing at elevated temperatures yield materials with moderately increased mechanical properties. A simple model accounting for defects in the regiospecificity, i.e. head-to-tail versus head-to-head or tail-to-tail monomer coupling, is introduced, in addition to side-chain dilution, to account for the low moduli of undoped samples. Doping with FeCl3 . 6H2O led to significant enhancement of the mechanical properties of the drawn samples, as well as to high electrical conductivity. As was previously found for other conducting polymer systems, strong correlations were observed between mechanical properties and electrical conductivity. The conductivity was found to scale linearly with tenacity, independent of side-chain length.