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Polar-molecules-driven enhanced colloidal electrostatic interactions and their applications in achieving high active electrorheological materials

Published online by Cambridge University Press:  31 January 2011

L. Xu
Affiliation:
Surface Physics Laboratory and Department of Physics, Fudan University, Shanghai 200433, People’s Republic of China
W.J. Tian
Affiliation:
Surface Physics Laboratory and Department of Physics, Fudan University, Shanghai 200433, People’s Republic of China
X.F. Wu
Affiliation:
Surface Physics Laboratory and Department of Physics, Fudan University, Shanghai 200433, People’s Republic of China
J.G. Cao
Affiliation:
Surface Physics Laboratory and Department of Physics, Fudan University, Shanghai 200433, People’s Republic of China
L.W. Zhou
Affiliation:
Surface Physics Laboratory and Department of Physics, Fudan University, Shanghai 200433, People’s Republic of China
J.P. Huang*
Affiliation:
Surface Physics Laboratory and Department of Physics, Fudan University, Shanghai 200433, People’s Republic of China
G.Q. Gu
Affiliation:
School of Information Science and Technology, East China Normal University, Shanghai 200062, People’s Republic of China
*
b) Address all correspondence to this author. e-mail: jphuang@fudan.edu.cn
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Abstract

We have fabricated a class of colloidal electrorheological (ER) fluids, in which suspended TiO2 particles were synthesized by a sol-gel method and modified by 1,4-butyrolactone molecules with a permanent molecular dipole moment of 4.524 D. Compared with pure TiO2 ER fluids, the quasi-static yield stress of the polar- molecules-modified ER fluid is enhanced as high as 48.1 kPa when subjected to an external electric field of 5 kV/mm. Also, it possesses other attractive characters such as low current density (<14 μA/cm2) and low sedimentation. Based on a Green’s function method, we present a first-principles approach to investigate colloidal electrostatic interactions. Excellent agreement between experiment and theory has been shown for the enhancement ratio of quasi-static yield stress, which quantitatively reveals that enough polar molecules oriented within the field-directed gap between the colloidal particles can unexpectedly enhance the interactions, thus yielding the unusual enhancement. This shows a promising and flexible direction for achieving more highly active ER materials.

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Copyright
Copyright © Materials Research Society 2007

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