Source:
Journal of Polymer Science, Part B: Polymer Physics, Volume 42, Number 17, p.3191-3203 (2004)
Accession Number:
2004717385
Abstract:
Small-angle neutron scattering (SANS) has been employed to study a blend of polystyrene and polybutadiene modified by copolymer additives. SANS data from the one-phase region approaching the phase boundary has been acquired for blends modified by random and diblock copolymers that have equal amts. of styrene and butadiene monomers as well as a random copolymer with an unequal monomer compn. The binary blend is near the crit. compn., and the copolymer concns. are low at 2.5% (wt./wt.). The data have been fitted with the RPA model (binary and multicomponent versions) to obtain Flory-Huggins interaction parameters (.chi.) for the various monomer interactions. These results are considered in the context of previous light scattering data for the same blend systems. The SANS cloud points are in good agreement with previous results from light scattering. The shifts in the phase boundary are due to the effects of the additives on the .chi. parameter at the spinodal. All the additives appear to lower the .chi. parameter between the homopolymers; this is in conflict with the predicted Flory-Huggins behavior.
