Abstract: The viscosimetric constants of aqueous suspensions of certain homoionic forms of montmorillonite and attapulgite were measured following adsorption of different kinds and quantities of organic polymers. Dissymmetry and interaction of the clay-organic complexes were then calculated from the Schulz-Blaschke equation and their structures deduced.
A positive, linear relationship was found between the dissymmetry of H- and Al-montmorillonite, respectively, and the amount of vinyl acetate maleic anhydride (VAMA) adsorbed-H-montmorillonite displayed the greater dissymmetry and it is inferred that H-montmorillonite complexes consist of an edge-to-edge linkage of clay particles through lattice-aluminum-carboxyl bonds. Al-montmorillonite permits three kinds of linkage: edge-to-edge (as with H-montmorillonite), external flat surface-to-surface (producing a “stacked” structure), and surface-to-edge, the last two involving exchangeable aluminum-carboxyl bonds. Edge-to-edge linkages probably predominate.
Ca-montmorillonite is unaffected by less than 8 parts of VAMA per thousand of clay. Edge-to-edge linked clay particles appear at this ratio and interaction diminishes. Delayed structural organization can be explained by low polymer adsorption at high initial pH. Maximum dissymmetry of H-montmorillonite-VAMA complexes occurred after titration with NaOH to pH between 6 and 8, above which mutual repulsion between highly dissociated polymer and clay may restrict linkage.
H-attapulgite-VAMA complexes are dissymmetrical for low VAMA adsorption but increased adsorption reduces dissymmetry and bundles of edge-to-edge linked particles are formed.
Probable structures of montmorillonite complexes with other polymers are also discussed.