Temperature- and pressure-dependent composition fluctuations in a polybutadiene/polystyrene polymer blend and diblock copolymer

Abstract

The phase diagram, the Flory-Huggins parameter Γ, and the Ginzburg parameter Gi of a polybutadiene/polystyrene blend and diblock copolymer were determined by small-angle neutron scattering in the pressure range of 0.1 and 200MPa. Both systems show qualitatively the same pressure dependence. The enthalpic and entropic terms of Γ are larger in blends. In the diblock copolymer a constant order-disorder temperature was observed which could be explained by a compensation effect between Γ and Gi.