The rheological behavior of the alkali metal salts of oligomeric sulfonated polystyrene (PS) ionomers was characterized using dynamic and steady shear measurements. The starting PS had a weight average molecular weight of 4000g∕mol and a narrow molecular weight distribution (1.06). Two sulfonation levels were examined, 2.5 and 4.8mol%, which corresponded, respectively, to one and two sulfonate groups per chain on average. The ionomers exhibited nanophase separation of an ion-rich phase, and as a consequence, time-temperature superposition failed for all samples. Sulfonation increased the melt viscosity of the ionomers, as much as seven orders of magnitude. The zero shear viscosity scaled as cq∕a, where c was the concentration of the ionic groups, q was the charge of the cation, and a was the cation radius, and although the molecular weight of the parent polystyrene was much lower than the entanglement molecular weight, the ionomer melts exhibited strong elastic behavior. The flow activation energy of the ionomers was similar to that of high molecular weight PS and the calculated molecular weight between “entanglements” of the ionomers was the same as for PS.

The dispersion and gelation of clay suspensions have major impact on a number of industries, such as ceramic and composite materials processing, paper making, cement production, and consumer product formulation. To fundamentally understand controlling mechanisms of clay dispersion and gelation, it is necessary to study anisotropic surface charge properties and colloidal interactions of clay particles. In this study, a colloidal probe technique was employed to study the interaction forces between a silica probe and clay basal plane/edge surfaces. A muscovite mica was used as a representative of 2:1 phyllosilicate clay minerals. The muscovite basal plane was prepared by cleavage, while the edge surface was obtained by a microtome cutting technique. Direct force measurements demonstrated the anisotropic surface charge properties of the basal plane and edge surface. For the basal plane, the long-range forces were monotonically repulsive within pH 6-10 and the measured forces were pH-independent, thereby confirming that clay basal planes have permanent surface charge from isomorphic substitution of lattice elements. The measured interaction forces were fitted well with the classical DLVO theory. The surface potentials of muscovite basal plane derived from the measured force profiles were in good agreement with those reported in the literature. In the case of edge surfaces, the measured forces were monotonically repulsive at pH 10, decreasing with pH, and changed to be attractive at pH 5.6, strongly suggesting that the charge on the clay edge surfaces is pH-dependent. The measured force profiles could not be reasonably fitted with the classical DLVO theory, even with very small surface potential values, unless the surface roughness was considered. The surface element integration (SEI) method was used to calculate the DLVO forces to account for the surface roughness. The surface potentials of the muscovite edges were derived by fitting the measured force profiles with the surface element integrated DLVO model. The point of zero charge of the muscovite edge surface was estimated to be pH 7-8.

The effect of weathering on the surface chemical composition and wettability of the oil sand solids and bitumen was studied by contact angle measurement, film flotation technique, XPS analysis, and ellipsometry thickness measurement. It was found that mild bitumen oxidation occurred during ore weathering. However, it has negligible effect on the bitumen surface wettability. In contrast, weathering forced more organic matters to adsorb onto the mineral solid surfaces, which made the solids more hydrophobic. A mechanism on how the organic matters adsorb on the solid surface due to weathering was put forward. The loss of the formation water due to weathering resulted in an intimate contact of bitumen with the mineral solids and thus offered the opportunity for the organic matters to adsorb, which was responsible for the enrichment of organic matters on the mineral solid surface. It was further observed that hot water washing partially removed the organic matters from the solids surface and hence decreased the solids hydrophobicity.

In oil sands processing, the separation of bitumen from sand grains is controlled by interfacial interactions between the bitumen and the sand. In this study, the effects of calcium and magnesium cations, surfactants, and their combination on the sand−bitumen interactions and consequently on bitumen liberation were investigated. Surface forces between silica and bitumen in industrial-plant process water and in water containing calcium and magnesium in amounts equivalent to those found in the plant process water were directly measured using an atomic force microscope. Zeta potential measurements were carried out for silica, bitumen, and their mixture to study the coagulation behavior between silica and bitumen. It was found that divalent cations are detrimental to bitumen liberation from sand grains because they decrease the long-range repulsive force and increase the adhesion force between silica and bitumen. On the other hand, surfactants were found to facilitate bitumen liberation by reducing silica−bitumen adhesion.

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