The gyroid: A new equilibrium morphology in weakly segregated diblock copolymers
- Princeton Univ., NJ (United States). Dept. of Physics
- Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Materials Science and Engineering
- Exxon Research and Engineering Co., Annandale, NJ (United States). Corporate Research Science Lab.
The authors report the identification of a new equilibrium microdomain morphology in an intermediate to weakly segregated diblock copolymer melt. A polystyrene-polyisoprene (SI) diblock copolymer consisting of 37 wt% styrene and of total M[sub w] = 27,400 was observed to transform from the lamellar morphology (in equilibrium at low annealing temperatures) to a new morphology at annealing temperatures approximately 50 C below the order-disorder transition (ODT). The transformation was observed to be thermoreversible. Investigation of the new morphology via small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) revealed the new structure to have remarkable three-dimensional long-range order, to belong to the cubic space group Ia3d, and to possess a bicontinuous cubic microstructure. From computer simulations of model structures and comparison with microscopy results, the authors propose models for the new morphology based on the triply periodic G minimal surface (gyroid) discovered by Schoen; similar morphologies have been observed in a variety of microphase-separated surfactant-water systems. Blends of this diblock with various short-chain homopolymers were used to investigate the compositional extent of the region of Ia3d stability on the phase diagram; the results indicate that the Ia3d phase is stable over a wide range of minority component volume fractions.
- DOE Contract Number:
- FG02-87ER60522
- OSTI ID:
- 6976411
- Journal Information:
- Macromolecules; (United States), Journal Name: Macromolecules; (United States) Vol. 27:15; ISSN MAMOBX; ISSN 0024-9297
- Country of Publication:
- United States
- Language:
- English
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