Morphology and phase diagram of complex block copolymers:  ABC linear triblock copolymers

Abstract

Using a real space implementation of the self-consistent field theory for the polymeric system, we explore microphases of ABC linear triblock copolymers. For the sake of numerical tractability, the calculation is carried out in a two-dimensional (2D) space. Seven microphases are found to be stable for the ABC triblock copolymer in 2D, which include lamellae, hexagonal lattice, core-shell hexagonal lattice, tetragonal lattice, lamellae with beads inside, lamellae with beads at the interface, and hexagonal phase with beads at the interface. By systematically varying the composition, triangle phase diagrams are constructed for four classes of typical triblock polymers in terms of the relative strengths of the interaction energies between different species. In general, when both volume fractions and interaction energies of the three species are comparable, lamellar phases are found to be the most stable. While one of the volume fractions is large, core-shell hexagonal or tetragonal phases can be formed, depending on which of the blocks dominates. Furthermore, more complex morphologies, such as lamellae with beads inside, lamellae with beads at the interface, and hexagonal phases with beads at the interface compete for stability with lamellae structures, as the interaction energies between distinct blocks become asymmetric. Our study provides guidance for the design of microstructures in complex block copolymers.

Effect of Architecture on the Tensile Properties of Triblock Copolymers in a Lamellar Phase

“…We found that these linear and star-shaped ABC terpolymers self-assemble into lamellar phases when using these parameters (Figure 3). The calculations agree with those of Yang et al [18,19] In our simulation, we select the relative deformation from À0.15 to + 0.15, and the corresponding free energies (the free energy of extension or shear) are calculated. Table 1 lists the dimensionless tensile moduli, obtained from Equation (17) for the triblock copolymer system, of lamellar structures having different molecular architectures (linear and star).…”

“…Consequently, the internal energy U should be written as being inversely proportional to the equilibrium domain size d*, that is, the thickness of the lamellae [Eq. (18)]: [32] U…”

“…Based on theoretical studies, linear and starlike block copolymers can assemble into similar ordered microstructures when their components and interaction energies between blocks are nearly identical. [18,19] Our focus in this investigation is to study the influence of the block copolymer architecture on the tensile properties of polymeric nanomaterials having lamellar phases.…”

Morphology of ABCD Tetrablock Copolymers Predicted by Self‐Consistent Field Theory

“…When the volume fraction of the middle block C is between 0.4 and 0.5 and that of the end block is about 0.2, the separated stable phase is two interpenetrating tetragonal lattices (CST 2 ). The similar phase (TET 2 ) was predicted theoretically [11,33] and observed experimentally [17][18][19] in the linear ABC triblock copolymer. The difference is that the adjacent blocks, A and B, form the core-shell phase, then form the core-shell tetragonal lattice, and the other minority D forms the other tetragonal lattice which interpenetrates the core-shell tetragonal lattice.…”

“…Until now, the morphologies and the phase diagrams for AB diblock copolymers, linear ABC triblock copolymer, and even ABC threemiktoarm copolymers have been intensively studied theoretically and experimentally. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Moreover, the more complicated block copolymers, such as those of linear ABCA, [20] ABCD, [21][22][23][24][25] ABCDE [23] types, and ABCD four-miktoarm star copolymer, [26] have been synthesized. Among these complicated tetrablock copolymers, only the morphology of the linear ABCA tetrablock copolymers has been studied theoretically; [27,28] a substitution of the end block A by a different block D, such as is the case Summary: We studied the two-dimensional (2D) microphase-separated morphology of linear ABCD tetrablock copolymers by self-consistent field theory.…”