Effect of shear on cubic phases in gels of a diblock copolymer

被引:60
作者
Hamley, IW [1 ]
Pople, JA
Fairclough, JPA
Terrill, NJ
Ryan, AJ
Booth, C
Yu, GE
Diat, O
Almdal, K
Mortensen, K
Vigild, M
机构
[1] Univ Leeds, Sch Chem, Leeds LS2 9JT, W Yorkshire, England
[2] Univ Sheffield, Dept Chem, Sheffield S3 7HF, S Yorkshire, England
[3] Univ Manchester, Dept Chem, Manchester M13 9PL, Lancs, England
[4] European Synchrotron Radiat Facil, F-38042 Grenoble, France
[5] Riso Natl Lab, Condensed Matter Phys & Chem Dept, DK-4000 Roskilde, Denmark
[6] SERC, Daresbury Lab, CLRC, Warrington WA4 4AD, Cheshire, England
关键词
D O I
10.1063/1.476108
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The effect of shear on the orientation of cubic micellar phases formed by a poly(oxyethylene)poly(oxybutylene) diblock copolymer in aqueous solution has been investigated using small-angle x-ray scattering (SAXS) and small-angle neutron scattering (SANS). SAXS was performed on samples oriented in a Couette cell using steady shear, and SANS was performed on samples subject to oscillatory shear in situ in a rheometer with a shear sandwich configuration. A body-centered-cubic (bcc) phase observed for gels with concentrations greater than 30 wt % copolymer was found to orient into a polydomain structure, with the close-packed {110} planes both parallel and perpendicular to the shear plane. For gels with 30 wt % copolymer or less, a face-centered-cubic (fcc) phase was observed, and this was also observed on heating the more concentrated gels that formed a bcc phase at room temperature. The fcc phase could be oriented to form a highly twinned structure, with a significant deviation from the ABCABC... stacking sequence of the ideal structure due to random sequences resulting from slip of {111} hexagonal-close-packed planes. For the lower concentration gels, a transition from hard to soft gel on increasing temperature was found to be characterized by a change in the susceptibility of the sample to macroscopic shear orientation, as probed using SAXS. The hard gel could be oriented by shear into a twinned fee structure, whereas the soft gel comprised a fee phase with a small grain size, which could not be sheared to form a macroscopically oriented domain. Shear only homogenized the sample, producing a powder SAXS pattern from a fcc structure. (C) 1998 American Institute of Physics.
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收藏
页码:6929 / 6936
页数:8
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