SCFT Study of Nonfrustrated ABC Triblock Copolymer Melts

ABSTRACT: The phase behavior of ABC triblock copolymer melts is studied by self-consistent-field theory (SCFT). We focus on “nonfrustrated ” triblocks, in which the Flory-Huggins interaction parameter łAC between the end blocks is significantly larger than that between the middle and either end block, i.e., łAC. łAB łBC. Such systems tend to form ordered structures with no AC interface. Complete phase triangles at fixed values of the products łijN are presented for a model with łAB) łBC, łAC and for a model with parameters chosen to represent poly(isoprene-b-styrene-b-ethylene oxide) copolymers that have recently been studied experimentally. Particular attention is paid to the structure of the orthorhombic O70 network phase and the reasons for its existence as well as to the sensitivity of the predicted phase behavior to changes in the ł parameters. 1