ABSTRACT:Electric conductivity and sol-gel transition behavior were studied for gels of a polydiacetylene poly[ 4,6-decadiyn-1, I 0-diol-bis(n-butoxy-carbonylmethyl urethane)] abbreviated to P(3BCMU). Two solvents with different dielectric constant were used, i.e., a-dichlorobenzene (o-DCB) and a mixed solvent of p-dichlorobenzene (p-DCB) and toluene (TOL). Temperature dependence of the shear moduli G' was measured to determine the gel-to-sol transition temperatures T, at which the moduli decreased steeply. The T, was 378 Kin o-DCB and 387 Kin p-DCBITOL (62138). Both direct current (DC) conductivity o-d, and alternating current (AC) conductivity 0"30 at I kHz exhibited a maximum around 368 and 362 K in o-DCB and p-DCBITOL, respectively. Dopant effects of an electron acceptor iodine and a donor tetrathiafulvalene TTF on o-do and o-" were also studied. o-" was enhanced approximately by 100 times with iodine but only by 5 times with TTF. The pronounced dopant effect indicates that the conduction in the gel state is partly due to electronic conduction through the P(3BCMU) chains. We also observed an appreciable strength of ionic conductivity in the sol and gel phases. The ionic conductivity in the gel phase was estimated from o-30 of the solvent containing the ions extracted from the gel phase. Then observed o-a, and o-d, were separated into the contributions of ionic and electronic conductions. Electronic conductivity increased with increasing dielectric constant of the solvent. Transition temperature T, where the color changed from blue to yellow was also determined by measuring the transmittance at 630 nm wave length. The temperature dependence of the transmittance indicated a hysteresis.KEY WORDS Electric Conductivity I Sol-Gel Transition I Polydiacetylene I Gel I Poly[ 4,6-decadiyn-1,10-diol-bis(n-butoxycarbonylmethyl urethane)] I P(3BCMU) I Among conducting polymers, derivatives of polydiacetylene with a relatively long side group are unique in a sense that they are soluble in a variety of organic solvents and form gel in poor solvents. 1 -4 In our previous papers, 1 • 2 we reported behavior of the reversible sol-gel transition and electric conduction in toluene (TOL) solution of poly[5,7-dodecadiyn-1,12-diol-bis(n-butoxy carbonyl methylurethane)] abbreviated to P(4BCMU). The alternating current (AC) conductivity O'ac at 1kHz and the direct current (DC) conductivity O'dc of P(4BCMU)/TOL gel exhibited a broad maximum around 336 K. Above this temperature, the() ac and() de decreased steeply with increasing temperature and reached to a level of an insulator. The O'ac and O'dc were enhanced approximately 20 times by doping with iodine.
