Influence of regiospecificity on the stability of electrical conductivity in photodoped poly(alkylthiophenes)

Summary form only given. Polymer structure plays a key role in electrical conductivity of poly(alkylthiophenes). The transport properties of conducting polymers depend drastically on the extend of intramolecular and intermolecular /spl pi/n-orbital overlap and on steric effects. Many kinds of synthetic methods were performed leading to different structure regularities and were studied in relation to their electrical conductivity behaviour: a) standard synthetic method by oxidative coupling with FeCl/sub 3/ giving random regiospecific structures, b) regiospecific synthetic method leading to regioregular polymers, c) reduction of the number of alkyl side chains in a regular way, d) Grignard-reagents coupling method, and e) copolymers of 3-rnethylthiophene and different alkylthiophenes. The doping of polymers was photoinitiated with optically dissociative materials (onium salts) which are incorporated with the basic poly(alkylthiophene) polymer in the spinning solution. The conditions of light exposure (wavelength range, exposure dose) and the concentration of photodopant used have been optimized to enhance the electrical conductivity as well as its stability. We report the results for these different structures. The influence of different atmospheres (nitrogen, dry air, humid air) and the effect of temperature on the degradation of the conductivity have also been studied. Under ambient conditions, a relative conductivity /spl sigma//spl sigma/sub o/, better than 1 has been found after more than 1000 hours, with a conductivity about 0.5 S/cm. High-resolution conducting patterns have been realized by microlithography techniques and their possible use in microelectronics have been investigated.