SMALL-ANGLE NEUTRON-SCATTERING AND LIGHT-SCATTERING STUDY ON THE MISCIBILITY OF POLY(STYRENE-RAN-BUTADIENE) POLYBUTADIENE BLENDS

The miscibility of binary blends of polybutadiene (PB) and poly(styrene-ran-butadiene) (SBR) was studied on the basis of segmental interaction parameters. In this analysis PB was assumed to be a random copolymer comprising 1,2-linkages (V) and 1,4-linkages (B) and SBR to be the one comprising styrene (S) and butadiene with V and B. The segmental interaction parameters between V and S (chi-vs), B and S (chi-BS), and V and B (chi-VB) were determined on the basis of the copolymer blend theory from the effective interaction parameters (chi-eff'S) for the blends of PB and SBR, and those for poly(styrene-b-butadiene-b-styrene) triblock copolymer (SBS), with different copolymer compositions and microstructures of polybutadienes. The values chi-eff were determined from either the small-angle neutron or X-ray scattering of the mixtures in the single-phase state. By use of these segmental interaction parameters, chi-VS, chi-BS, and chi-VB, the miscibility of the SBR/PB blends was predicted for a given set of V, B, and S contents in PB and SBR. The predictions of the miscibility for several SBR/PB blends agreed well with the results of the light scattering experiments.