LAMELLAR DOMAIN SPACINGS OF DIBLOCK COPOLYMER HOMOPOLYMER BLENDS AND CONFORMATIONS OF BLOCK CHAINS IN THEIR MICRODOMAINS/

Lamellar domain spacings (D) of blends of a styrene-2-vinylpyridine (S P) diblock copolymer and homopolymers corresponding to the block polym ers (S and/or P), of which molecular weights are lower than that of th e block polymer, were examined by small-angle X-ray scattering (SAXS), and the dimensions of block chains in the lamellae were investigated by small-angle neutron scattering (SANS). The D's for SP/S/P ternary a nd SP/S (or SP/P) binary blends increase with increasing the molecular weight of the homopolymers, M-H, as well as the volume fraction of th e homopolymers, Phi(H), in the corresponding lamella. The variations o f the D's with Phi(H) for the blends with homopolymers having differen t M-H's reveal that homopolymers with higher M-H are localized at the center of the corresponding lamella, while those with lower M-H are di stributed throughout the lamella. Moreover, the comparison between the D's for ternary and binary blends with homopolymers having equal M-H' s implies that the homopolymers in binary blends are more localized th an those in ternary blends. In these ternary and binary blends the rad ii of gyration of styrene block chains along the direction parallel to lamellar interface are not much different from that for a pure dibloc k copolymer irrespective of Phi(H) as well as M-H.