ELECTRICAL-CONDUCTIVITY OF POLYDIACETYLENE, POLY[5,7-DODECADIYN-1,12-DIOL-BIS(N-BUTOXY CARBONYLMETHYL URETHANE)] GEL - SOL-GEL TRANSITION AND CONDUCTION MECHANISM

Electrical conductivity, colour change and sol-gel transition behaviou r were studied for a polydiacetylene, poly[5,7-dodecadiyn-1,12-diol-bi s(n-butoxy carbonylmethyl urethane) abbreviated as P(4BCMU), in toluen e gels. For P(4BCMU)-28 with weight average molecular weight of 280 00 0, the sol-gel transition temperature was determined to be around 348 K varying slightly depending on the methods employed for the determina tion. The alternating current (a.c.) and direct current (d.c.) conduct ivities of P(4BCMU)-28 gels exhibited a broad maximum at approximately 336 K. Upon heating the gels, the colour changed from red to yellow a t approximately 348 K, while upon cooling a sharp colour change was ob served at approximately 340 K indicating the supercooling of the sol p hase. These characteristic temperatures increased with increasing mole cular weight. The a.c. and d.c. conductivities were enhanced approxima tely 20 times by adding a dopant iodine to the gels. We also observed a weak photoconductivity similar to the bulk P(4BCMU). These results s uggest that the conduction mechanism of the gels is due predominantly to electronic origins through the gel networks rather than ionic ones in the toluene medium.