Intrachain conduction and main-chain conformation of conducting polymers as studied by frequency-domain electric birefringence spectroscopy

Summary form only given. The single-chain dynamics of a typical soluble conducting polymer, poly(3-hexylthiophene) (P3HT), has been studied in solutions by the frequency-domain electric birefringence (FEB) spectroscopy. From the results, we obtained information on the intrachain conduction mechanism exclusively without the interference from the interchain one as well as on a close correlation between the conduction mechanism and the main-chain conformation. As the fraction of toluene in solvents mixed with methylene chloride increased, the polymer conformation changed from an extended form to a coiled one (the rod-coil transition). On the other hand, it was clearly revealed that there exist two kinds of transports of carriers along the polymer chain with different diffusion distances and diffusion constants in the intrachain conduction of P3HT in pure methylene chloride. Although the faster diffusion constant D/sub H/ within the shorter range has been reported for other conducting polymers by NMR and ESR measurements, the slower diffusion constant D/sub M/ within the longer distance up to the contour length of the conducting polymer is first revealed in the present study by the FEB technique. Thus the FEB spectroscopy is a useful technique for the investigation of the conduction mechanism in the conducting polymers.