S-Space College of Engineering/Engineering Practice School (공과대학/대학원) Dept. of Chemical and Biological Engineering (화학생물공학부) Journal Papers (저널논문_화학생물공학부)
Interplay between Cubic and Hexagonal Phases in Block Copolymer Solutions
|dc.contributor.author||Park, Moon Jeong||-|
|dc.identifier.citation||Langmuir, 2005, 21, 1403-1411||en|
|dc.description.abstract||The phase behavior of a symmetric styrene−isoprene (SI) diblock copolymer in a styrene-selective solvent, diethylphthalate, was investigated by in situ small-angle X-ray scattering on isotropic and shear-oriented solutions and by rheology and birefringence. A remarkable new feature in this phase diagram is the coexistence of both body-centered cubic (bcc) and hexagonally close-packed (hcp) sphere phases, in a region between close-packed spheres (cps) and hexagonally packed cylinders (hex) over the concentration range ≈ 0.33−0.45. By focusing on the transitions among these various ordered phases during heating and cooling cycles, we observed a strong hysteresis: supercooled cylinders persisted upon cooling. The stability of these supercooled cylinders is quite dependent on concentration, and for ≥ 0.40, the supercooled cylinders do not revert to spheres even after quiescent annealing for 1 month. The spontaneous formation of spheres due to the dissociation of cylinders is kinetically hindered in this case, and the system is apparently not amenable to any pretransitional fluctuations of cylinders prior to the cylinder-to-sphere transition. This contrasts with the case of cylinders transforming to spheres upon heating in the melt. The application of large amplitude shear to the supercooled cylinders is effective in restoring the equilibrium sphere phases.||en|
|dc.description.sponsorship||This work was supported primarily by the MRSEC Program of the National Science Foundation under Award No. DMR-0212302. Portions of this work were performed at the DuPont-Northwestern-DowCollaborative AccessTeam(DND-CAT) Synchrotron Research Center located at Sector 5 of the Advanced Photon Source.DND-CATis supported by the E.I. DuPont de Nemours&Co., The Dow Chemical Company, the U.S. National Science Foundation through grant DMR-9304725, and the State of Illinois through the Department of Commerce and the Board of Higher Education Grant IBHEHECANWU96. Use of the Advanced Photon Source was supported by the U.S. Department of Energy, Basic Energy Sciences, Office of Science, under Contract No. W-31-109-Eng-38, and use of the Pohang Light Source (PLS) was supported by Ministry of Science and Technology of Korea. We are grateful to the Brain Korea 21 Program endorsed by the Ministry of Education of Korea and to Prof.||en|
|dc.publisher||American Chemical Society||en|
|dc.title||Interplay between Cubic and Hexagonal Phases in Block Copolymer Solutions||en|
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