Abstract
We compute phase diagrams for diblock copolymers in the mean-field weak-segregation regime as a function of the fraction f of A-monomers and the repulsive interaction χN. We include the ordered bicontinuous double-diamond (OBDD) phase [space group Pn3m] and the gyroid phase [space group Ia3d] as well as lamellae, hexagonal cylinders, and BCC spheres. We find a stable region of gyroid phase between cylinders and lamellae just above the mean-field critical point, in agreement with numerical mean-field calculations. The stability of gyroid depends on the presence of the next higher [220] reflections in addition to the [211] fundamental. The gyroid free energy is favored by terms of the form ψ[211]3ψ[220] and ψ[211]2ψ[220]; the analogous terms are not permitted for OBDD.
Original language | English (US) |
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Pages (from-to) | 249-255 |
Number of pages | 7 |
Journal | Journal de Physique I |
Volume | 7 |
Issue number | 2 |
State | Published - Dec 1 1997 |
All Science Journal Classification (ASJC) codes
- Statistical and Nonlinear Physics
- General Engineering