CHARACTERIZATION OF POLY(3-OCTYLTHIOPHENE) .2. MELT RHEOLOGICAL CHARACTERIZATION

The poly(3-alkythiophenes) are electrically conducting polymers which are of particular interest due to their melt-processibility. We have s tudied the melt properties of poly(3-octylthiophene) (P3OT) by dynamic theological measurements at temperatures between 180 and 250 degrees C. The samples investigated have molecular weights in the range M(w) = 30,000 to 400,000 and have been carefully characterized by dilute sol ution techniques. Residual iron chloride, a reagent used in the polyme rization of these materials, was found to cause a high degree of cross linking in the polymer melt. By contrast, samples which had been caref ully purified demonstrated a negligible rate of crosslinking in a nitr ogen atmosphere; however, the presence of air and higher temperatures were found to increase the rate of crosslinking substantially. The tem perature dependence of the viscoelastic properties was characterized a ccording to the principles of time-temperature superposition, and the influence of molecular weight was also evaluated. Overall, the theolog ical behavior was determined to be similar to that commonly observed f or linear flexible polymers, which is in agreement with the results of our solution characterization of these materials.