Shear-banding and microstructure of colloids in shear flow

被引:64
作者
Dhont, JKG
Lettinga, MP
Dogic, Z
Lenstra, TAJ
Wang, H
Rathgeber, S
Carletto, P
Willner, L
Frielinghaus, H
Lindner, P
机构
[1] Forschungszentrum Julich, IFF Weiche Mat, D-52425 Julich, Germany
[2] Forschungszentrum Julich, IFF Neutronen Streuung, D-52425 Julich, Germany
[3] Inst Max Von Laue Paul Langevin, F-38042 Grenoble 9, France
关键词
D O I
10.1039/b205039k
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
We shall discuss the following phenomena found in various colloidal systems in shear flow. We recently observed shear-banding in suspensions of fd-virus in a cylindrical shear cell. Small angle light scattering experiments revealed that the shear-banding transition is preceded by a relatively fast process ( minutes) of nematic-to-paranematic phase separation during which inhomogeneities on the micrometer length scale are formed. After the formation of these inhomogeneities, a slow ( hours) appearence of shear-bands is observed, which have a height of a few mm. In the stationary state it is found, by means of polarization microscopy, that inhomogeneities exist within the bands. Small angle, time resolved light scattering experiments on near-critical microstructural order in a mixture of colloidal spheres and free polymer under stationary shear flow are discussed. The unexpected distortion of microstructure in directions perpendicular to the flow direction is quantitatively explained by extending an already existing theory, to include shear-induced short-ranged microstructural distortion. In colloidal systems consisting of hairy colloids, where a spherical core is decorated with relatively long polymers, shear-induced polymer brush deformation might be important for its structural and rheological behavior. Preliminary neutron scattering and rheology experiments are performed to study polymer brush deformation in (semi-) dilute suspensions.
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页码:157 / 172
页数:16
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