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Controlling Clusters of Colloidal Platelets: Effects of Edge and Face Surface Chemistries on the Behavior of Montmorillonite Suspensions
journal contribution
posted on 2015-12-17, 07:59 authored by William
J. Ganley, Jeroen S. van DuijneveldtThe structural and rheological consequences
of adsorbing pyrophosphate
anions to the edges and polyetheramines to the faces of montmorillonite
platelets in aqueous suspension were investigated. Oscillatory rheology
and scattering experiments showed that the two surface treatments
act in different regions of the phase diagram and that this can be
attributed to modifications of local particle interactions resulting
in changes to the behavior and morphology of platelet clusters. The
polyetheramine was found to neutralize surface charge, reducing electrostatic
repulsion between platelets and therefore allowing them to come into
closer proximity. This reduces the effective volume fraction of the
clusters and reverses jamming in low ionic strength arrested phases.
Conversely, the adsorption of pyrophosphate was found to introduce
a high concentration of negative charge to the particle edge, resisting
the formation of bonded percolating gels at high ionic strength. The
two separate surface chemistries can be applied in parallel with no
adverse effects and thus have the potential to be applied to dual
functionalization of two-dimensional colloids such as platelets. This
has implications for finer formulation design where targeted rheology
modification could be achieved by careful selection of chemistry at
one surface accompanied by an additional function at the other.
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Keywords
polyetheramineadsorbing pyrophosphate anionsparticle interactionsstrengthControlling Clusterssurface treatments actmontmorillonite plateletsparticle edgeOscillatory rheologyrheology modificationFace Surface Chemistriesplatelet clustersColloidal Plateletsvolume fractionsurface chargerheological consequencesformulation designMontmorillonite SuspensionsThesurface chemistriesphase diagram