DIELECTRIC NORMAL MODE PROCESS IN BINARY BLENDS OF POLYISOPRENE .1. EXCLUDED VOLUME EFFECT IN UNDILUTED BINARY BLENDS

The excluded volume effect in chemically homologous polymer blends was studied by dielectric normal mode spectroscopy on binary blends of narrow molecular weight distribution cis-polyisoprenes (cis-PI). Dielectric measurements of the mean-square end-to-end distance (r2) of the high molecular weight cis-PI component (hmc) were carried out on the blends containing 0.5–5% hmc with the degree of polymerization (DP) = P2 in low molecular weight cis-PI (lmc) with DP = P1 In dilute blends of P21/2/P1 being larger than unity, (r2) of hmc was greater than the unperturbed value, as predicted earlier by Flory. In some semidilute blends containing 5% hmc of P2 > 300, the expansion factor α2 of (r2) became independent of P2. This behavior was qualitatively in agreement with the theory of Joanny et al. © 1990, American Chemical Society. All rights reserved.