THE EFFECT OF MOLECULAR-WEIGHT AND CRYSTALLINITY ON THE CONDUCTIVITY OF A CONDUCTING POLYMER

Recent theories have related the molecular-weight dependence of the co nductivity of a conjugated polymer to the relative importance of inter chain and intrachain charge transport processes. This prompted an expe rimental search for this effect using a series of fractionated poly(3- octylthiophenes). No significant molecular-weight dependence was found over the range 30 000 less-than-or-equal-to M(w) less-than-or-equal-t o 400 000, indicating that interchain transport does not limit the mac roscopic conductivity of these samples. However, even small difference s in the degree of crystallinity among the polymer samples were determ ined to have a profound effect on the conductivity.