Thermodynamics of Polymer Blends Organized by Balanced Block Copolymer Surfactants Studied by Mean-Field Theories and Scattering

Parameters determined from binary experiments were used to predict the behavior of multicomponent A/B/A−C polymer blends, where A is saturated polybutadiene with 90% 1,2-addition (sPB90), B is polyisobutylene (PIB), and C is also saturated polybutadiene but with 63% 1,2-addition (sPB63). The polymers were chosen such that the binary interactions (A/B, A/C, and B/C) are analogous to those in oil (A)/water (B)/nonionic surfactant (A−C) systems, where A/B and A/C are unfavorable interactions (χ > 0) and B/C is a favorable interaction (χ < 0). The Flory−Huggins interaction parameters (χ_AB, χ_AC, and χ_BC) and the statistical segment lengths (l_A, l_B, and l_C) were all determined experimentally by fitting the random phase approximation (RPA) to small-angle neutron scattering (SANS) data from the three binary homopolymer blends. These parameters were successfully used to predict the scattering from concentration fluctuations in a homogeneous A/B/A−C blend using multicomponent RPA. These same binary parameters were also used as the only inputs to self-consistent field theory (SCFT) calculations of ordered multicomponent polymer blends. The SCFT calculations enabled quantitative interpretation of the SANS profiles from microphase separated A/B/A−C blends. The phase separation temperatures predicted by theory for the blends were within the experimental error, and the theoretical domain spacings were within 10% of the experimental values.