DIELECTRIC NORMAL MODE RELAXATION OF PROBE POLYISOPRENE CHAIN IN SEMIDILUTE POLYBUTADIENE SOLUTIONS .2. DYNAMIC BEHAVIOR

Dynamics of a trace amount of cis-polyisoprene (PI) dissolved in semid ilute polybutadiene (PB)/n-heptane (Hep) solutions as a probe was exam ined through dielectric normal mode relaxation studies and compared wi th the results of semidilute PI/Hep solutions. In PI/Hep solutions, th e logarithm of the normal mode relaxation time tau of PI increased lin early with PI concentration Cl, and log tau values for different PI mo lecular weight M(I) were superposed by plotting against C(I)[eta]I wit h [eta]I being the intrinsic viscosity of PI in Hep. For the PI/PB/Hep ternary solutions of varying PB concentration C(B) and molecular weig ht M(B), the data of tau reduced by tau0 at the infinite dilution were plotted against the reduced concentrations C(B)[eta]B and C(B)[eta]I. We found that data of tau/tau0 were expressed by a universal function of such two parameters C(B)[eta]B and C(B)[eta]I. The log(tau/tau0) v s log(C(B)[eta]I) curves under constant C(B)[eta]B exhibited a sigmoid al shape, becoming independent of C(B)[eta]I at high C(B)[eta]I. The l og(tau/tau0) vs log(C(B)[eta]B) curves under constant C(B)[eta]I were also cast into a universal curve of a sigmoidal shape. These curves we re thus divided into three regimes in which the dynamics of the probe PI chains can be explained by a nondraining Zimm model, by a free-drai ning Rouse model, and by a reptation model reflecting entanglements am ong the PI and matrix PB chains.