Shear-induced ordering of lamellar and gyroid structures observed in a nonionic surfactant/water system |
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Authors: | M Imai K Nakaya T Kato |
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Institution: | (1) Department of Physics, Faculty of Science, Ochanomizu University, Bunkyo, Tokyo 112-0012, Japan, JP;(2) Graduate School of Science, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan, JP |
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Abstract: | The shear-induced ordering of lamellar and gyroid structures of a nonionic surfactant C16E7/D2O system in a Couette shear cell ( 0.001 < < 10 s-1, : shear rate) has been investigated by using a small angle neutron scattering technique. In the lamellar phase, the steady
shear flow having > 0.01 s-1 suppresses undulation fluctuations of lamellae (Maxwell effect). This suppression of fluctuations brings two effects; 1)
shear-induced lamellae ordering toward a parallel orientation and 2) obstruction of a lamellar↦gyroid transition. It is quite
interesting to note that there is a characteristic shear rate range ( 0.01 < < 0.3 s-1), where both effects take place. We have also investigated the shear effects on the gyroid phase. Below the characteristic
shear rate range, the gyroid structure keeps three-dimensional network lattice, while above the characteristic shear rate
range, the gyroid structure transforms to the parallel orientation lamellae (shear-induced gyroid-lamellar transition). Thus
the shear flow having the characteristic shear rate plays very important roles in shear ordering phenomena.
Received 26 June 2000 and Received in final form 12 January 2001 |
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Keywords: | PACS 83 50 Ax Steady shear flows viscometric flow – 68 55 Jk Structure and morphology thickness crystalline orientation and texture – 64 70 Md Transitions in liquid crystals |
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