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

Abstract

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, χAC, and χBC) and the statistical segment lengths (lA, lB, and lC) 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.

Microphase and Macrophase Separation in Multicomponent A/B/A−C Polymer Blends with Attractive and Repulsive Interactions

“…Our synthesis and characterization procedures are described in ref 34. Polybutadiene was synthesized via anionic polymerization.…”

“…Binary and multicomponent blends were created via methods described in ref 34. The samples were pressed between two quartz disks and then annealed at 90°C (unless otherwise specified) for 10 min to erase the effects of the shearing force applied to the sample during pressing.…”

“…N j of deuterated components are equal to that of their hydrogenated counterparts. All definitions and equations are described fully in ref 34.…”

“…Periodic structures are described using self-consistent field theory (Appendix B of ref 34). [56][57][58] In these phases, the volume fractions of the components, φ i,m , are periodic functions of position.…”

“…[32][33][34][35][36][37][38][39][40][41] In this article, we use an A-C diblock copolymer to organize A and B homopolymers. The C block is designed to have attractive interactions with the B homopolymer and repulsive interactions with the A homopolymer.…”