DIELECTRIC NORMAL MODE PROCESS IN BINARY BLENDS OF POLYISOPRENE .2. DYNAMIC BEHAVIOR

The dielectric behavior was studied on binary blends through observation of the normal mode relaxation time τn of a small amount of a test chain component blended with a matrix component, both of which were narrow molecular weight cis-polyisoprenes (cis-PIs). The test chain was a low molecular weight component (lmc) and the matrix a high molecular weight component (hmc) and vice versa. The τn of the lmc test chain was somewhat increased from that of its pure undiluted state: when the molecular weight Mw of the lmc test chain was higher than 3000, the τn was proportional to Mw 3.0. The behavior is in agreement with the original tube theory proposed by de Gennes. For the binary blends composed of an hmc test chain and an lmc matrix, the τn of the hmc test chain was first corrected for the excluded volume effect by using the data of the expansion factor reported in part 1. The slope of the resulting double logarithmic plot of τn vs Mw of the hmc test chain was 1.9 in the lmc matrix of Mw = 1600, while the slope decreased to 1.6 for the lmc matrix with Mw≤1000. The results suggest that the hydrodynamic nondraining effect becomes significant in the lmc matrix of Mw<1000. The widths of the loss curves reflecting the distribution of relaxation times of the test components were almost the same among the two types of the blends as well as those of the corresponding monodisperse cis-PIs. © 1990, American Chemical Society. All rights reserved.