Flow mechanisms in the face-centred cubic micellar gel of a diblock copolymer |
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Authors: | V Castelletto I W Hamley Z Yang |
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Institution: | (1) School of Chemistry University of Leeds Leeds LS2 9JT, UK, GB;(2) Department of Chemistry University of Manchester Manchester M13 9PL, UK, GB |
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Abstract: | The mechanisms of flow of a face-centred cubic micellar phase were investigated using small-angle X-ray scattering (SAXS)
for samples under either steady or oscillatory shear in two different geometries: Couette cell and planar shear sandwich.
The system studied was a gel formed by a poly(oxyethylene)–poly(oxypropylene) diblock copolymer in water. SAXS indicated that
under steady shear in a Couette cell, flow occurs via sliding of hexagonal close-packed (hcp) layers with a close-packed 110]
direction along the shear direction. Under oscillatory shear in the planar shear sandwich, coexistence between this orientation
and one in which the hcp layers are rotated by 30° (and flow is in a 211] direction) was observed; however, when subject
to oscillatory shear in the Couette cell, flow only occurred along a 110] direction. This observation of flow in a non-close-packed
direction may be due to alignment induced by the walls of the shear sandwich.
Received: 24 February 2001 Accepted: 21 March 2001 |
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Keywords: | Block copolymers Micelles Gels Shear Small-angle x-ray scattering |
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