期刊
SCIENCE
卷 330, 期 6002, 页码 349-353出版社
AMER ASSOC ADVANCEMENT SCIENCE
DOI: 10.1126/science.1195552
关键词
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资金
- Department of Energy [4000041622]
- National Science Foundation [DMR-0704192]
- University of Minnesota Materials Research Science and Engineering Center (MRSEC)
- E. I. Dupont de Nemours Company
- Dow Chemical Company
- State of Illinois
- U.S. Department of Energy, Office of Science, Basic Energy Sciences [DE-AC02-06CH11357]
- NSF through National Nanotechnology Infrastructure Network
Sphere-forming block copolymers are known to self-assemble into body-centered cubic crystals near the order-disorder transition temperature. Small-angle x-ray scattering and transmission electron microscopy experiments on diblock and tetrablock copolymer melts have revealed an equilibrium phase characterized by a large tetragonal unit cell containing 30 microphase-separated spheres. This structure, referred to as the sigma (sigma) phase by Frank and Kasper more than 50 years ago, nucleates and grows from the body-centered cubic phase similar to its occurrence in metal alloys and is a crystal approximant to dodecagonal quasicrystals. Formation of the s phase in undiluted linear block copolymers (and certain branched dendrimers) appears to be mediated by macromolecular packing frustration, an entropic contribution to the interparticle interactions that control the sphere-packing geometry.
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