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Title: Rheology and structure of suspensions in liquid crystalline hydroxypropylcellulose solutions
Authors: Hoekstra, Johannes ×
Vermant, Jan
Mewis, Joannes
Narayanan, T #
Issue Date: Jul-2002
Publisher: Amer chemical soc
Series Title: Langmuir vol:18 issue:15 pages:5695-5703
Abstract: The rheology and flow-induced microstructure of filled liquid crystalline polymers (LCPs) are studied. The matrix consists of hydroxypropylcellulose in water. The particle diameters are 28 and 3000 nm, i.e., ranging from the textural length scale to 100 times smaller. Contrary to earlier results in the literature, small amounts of the smallest particles did not induce a drop in viscosity. Even very small amounts of particles of either size eliminate or drastically shift the shear rate region where the first normal stress differences are negative. This is associated with a reduction in flow-induced ordering as detected with X-ray scattering. Different methods to deduce ordering from the SAXS data are compared. Using light scattering a substantial change in texture, due to the presence of the fillers, can be detected. Transient experiments indicate that texture still governs the rheology of filled LCPs. The characteristic time scales of the transients are reduced by the presence of fillers, which is consistent with a reduction in textural length scale. The latter causes an additional increase in viscosity when adding particles. This is not the case for N-1, which is more affected by global orientation than by texture as such. The structure factor of the particles has been measured, using SAXS, in a suspension with a volume fraction of 0.1. The particle structure remains essentially liquidlike and is not affected by shear in the range of shear rates covered here. The ordering effects that can be observed in low molecular weight LCs do not appear in the LCPs studied here.
URI: 
ISSN: 0743-7463
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Soft Matter, Rheology and Technology Section
Chemical Engineering - miscellaneous
× corresponding author
# (joint) last author

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