Lamellar phase of a symmetric triblock copolymer

Abstract

We study the lamellar phase formed by symmetric ABA triblock copolymers with degree of polymerization N and A monomer fraction f. Employing a mean-field, lattice formalism, we calculate the fraction of copolymers which bridge the B-rich lamellae. This fraction is found to be significant, although it is strictly bounded above by l/~ within the formalism. Once the lamellar phase is strongly segregated, the fraction of bridges decreases slowly with increasing N, increasing Flory parameter x, and decreasing f. In the strong-segregation limit, the lamellar spacing D is found to scale as D - N0xb with a = 0.68 and b = 0.19. The interfacial width 5 does not scale as a power of N but does scale with x as 5 - xc, where c = -0.51. Both D and 5 are nearly independent off. 187