DIELECTRIC NORMAL MODE RELAXATION OF PROBE POLYISOPRENE CHAIN IN SEMIDILUTE POLYBUTADIENE SOLUTIONS .1. END-TO-END DISTANCE

Dielectric normal mode relaxation of a trace amount of cis-polyisopren e (PI) mixed in semidilute heptane (Hep) solutions of polybutadiene (P B) was studied and compared with semidilute PI/Hep solutions. The prob e PI chains have the dipole moments aligned in the same direction para llel to the chain contour, but the matrix PB chains do not. Thus we ca n observe dynamic and conformational properties of the probe PI chains alone. In this part 1, the concentration dependence of the mean squar e end-to-end distance [r2] of PI was compared to those in PI/Hep and P I/PB/Hep solutions. In PI/Hep, the [r2] decreased with PI concentratio n C(I) in proportion to C-0.152. The exponent agreed well with the sca ling theory of Daoud and Jannink with the Flory exponent nu = 0.56. In PI/PB/Hep the C(I) was fixed to be 0.2 or 0.4 wt % and the PB concent ration C(B) was changed over a wide range from dilute to semidilute re gimes. In the case where the molecular weight M(I) of PI is larger tha n that of PB (M(B)), the [r2] of the PI chains divided by [r2]o in dil ute PI/Hep solution was plotted against C(B)[eta]B (with [eta]B being the intrinsic viscosity of PB in Hep) and yielded a universal curve, w hereas for those with M(I) less-than-or-similar-to M(B), a universal c urve was obtained simply by plotting [r2]/M(I) against C(B). The resul ts were favorably compared with the scaling theories developed by Joan ny et al. and Nose.