Shear-induced ordering of lamellar and gyroid structures observed in a nonionic surfactant/water system

M. Imai; K. Nakaya; T. Kato

doi:doi:10.1007/s101890170046

2021 Impact factor 1.624

Soft Matter and Biological Physics

Eur. Phys. J. E 5, 391-402 (2001)

Shear-induced ordering of lamellar and gyroid structures observed in a nonionic surfactant/water system

M. Imai¹, K. Nakaya¹ and T. Kato^{1, 2}

¹ Department of Physics, Faculty of Science, Ochanomizu University, Bunkyo, Tokyo 112-0012, Japan
² Graduate School of Science, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan

imai@phys.ocha.ac.jp

(Received 26 June 2000 and Received in final form 12 January 2001 )

Abstract
The shear-induced ordering of lamellar and gyroid structures of a nonionic surfactant C₁₆E₇/D₂O system in a Couette shear cell ( $0.001 < \dot{\gamma} < 10$ s^-1, $\dot{\gamma}$ : shear rate) has been investigated by using a small angle neutron scattering technique. In the lamellar phase, the steady shear flow having $\dot{\gamma} > 0.01$ 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 $\to$ gyroid transition. It is quite interesting to note that there is a characteristic shear rate range ( $0.01 < \dot{\gamma} < 0.3$ 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.

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.

© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001