ELECTRIC-CONDUCTIVITY, ELASTICITY, AND OPTICAL-SPECTRA IN BLEND GELS OF POLYDIACETYLENES - P(3BCMU) P(4BCMU) MIXED-SOLVENT SYSTEM

Alternating current conductivity sigma(ac), shear moduli G', and ultra violet-spectra (UV) were studied for gels consisting of two polydiacet ylenes i.e., 4,6-decadiyn-1,10-diol-bis(n-butoxy-carbonylmethyl uretha ne)] abbreviated as P(3BCMU) and poly[5,7-dodecadiyn-1,12-diol-bis(n-b utoxy carbonyl methylurethane)] abbreviated as P(4BCMU). As a common s olvent of these polydiacetylenes, a mixed solvent p-dichlorobenzene (p -DCB)/toluene (TOL) (62/38) was used. Shear moduli G' of blend gels de creased stepwise around 340 and 385 K which coincided with the gel-to- sol transition temperatures of pure P(4BCMU) and P(3BCMU) gels, respec tively. At 385 K the blend gels transformed completely into sol. Obser ved G' of blend gels conformed approximately to the additivity law wit h respect to the weight fraction of P(3BCMU) and P(4BCMU). This indica tes that in the range of T<340 the gel network is composed of both the P(4BCMU) and P(3BCMU) molecules but above 340 K the network is compos ed only of the P(3BCMU) molecules. Temperature dependence of sigma(ac) at 1 kHz exhibited two maxima around 330 and 360 K. sigma(ac) observe d around 360 K was ca. ten times higher than sigma(ac) expected from t he additivity. The UV spectra of the blend gels exhibited abosorption bands not seen in pure gels of the components. It is speculated that t he P(3BCMU) and P(4BCMU) chains partially form a charge transfer compl ex in blend gels.