Interfaces in Diblocks:  A Study of Miktoarm Star Copolymers

Abstract

We study ABn miktoarm star block copolymers in the strong segregation limit, focusing on the role that the AB interface plays in determining the phase behavior. We develop an extension of the kinked-path approach which allows us to explore the energetic dependence on interfacial shape. We consider a one-parameter family of interfaces to study the columnar to lamellar transition in asymmetric stars. We compare with recent experimental results. We discuss the stability of the A15 lattice of spherelike micelles in the context of interfacial energy minimization. We corroborate our theory by implementing a numerically exact self-consistent-field theory to probe the phase diagram and the shape of the AB interface.

Morphology diagrams forA2Bcopolymer melts: real-space self-consistent field theory

“…Also, we have found the PL and a micelle-like (M) morphology to be metastable for the A 2 B miktoarms with symmetric A arms. This is in agreement with other literature studies carried out using spectral SCFT [22] and in disagreement with a DPD [24] study. Furthermore, comparison of the morphology diagrams for A 2 B copolymers containing symmetric and asymmetric arms reveal that architectural asymmetry of A arms aids the microphase separation.…”

“…1(b)). Both, the SCFT [22] and DPD [24] studies have already chalked out the morphology diagrams for A 2 B copolymers with symmetric A arms. However, the SCFT study [22] has been carried out using spectral methods, where one has to presume the symmetry of morphologies.…”

“…Both, the SCFT [22] and DPD [24] studies have already chalked out the morphology diagrams for A 2 B copolymers with symmetric A arms. However, the SCFT study [22] has been carried out using spectral methods, where one has to presume the symmetry of morphologies. Furthermore, worm-like micelles are observed in the DPD simulations [24] in contrast to the sphere or cylindrical phase in the SCFT near the disorder-order transition around φ B = 0.8.…”

“…The theory by Milner [11] accounts for the fact that the two kinds of blocks may differ in conformational characteristics, which results in a variation in the arms stretching at the junction point. Self-consistent field theory (SCFT) studies bridging the gap between the weak and strong segregation theories were done by Grason et al [7,22,23]. Furthermore, dissipative particle dynamics (DPD) simulations [24] have been used to construct the morphology diagrams for A 2 B copolymer melts and reasonable agreement with the SCFT predictions [7,23] has been established with the addition of new morphologies.…”

Self-consistent field theory of multiply branched block copolymer melts

“…In general, it is not possible to evaluate the functional integrals in (8). Nevertheless, in the limit where N is large, fluctuation contributions to the partition function are small, and the integral is dominated by its saddlepoint, where the free energy per chain, − kB T n ln Z, is minimal [18,19] .…”