Physicochemical studies of clay polymer interactions.

This thesis reports investigations into the colloid and solid state properties of clay/polymer complexes. The interactions between water soluble polymers and clay were investigated because of their importance to the oil industry which make use of clay/polymer interactions to control certain properties of drilling muds. [133]Cs and to a lesser extent [23]Na NMR have been evaluated as novel in situ probes to study the adsorption of polycations, and other cationic species, onto 25 gL[-1] suspensions of Westone-L. Westone-L is a low iron containing montmorillonite which was completely exchanged with either Cs[+] or Na[+] cations. The polycations FL15, FL16 and FL17, of general formula [(Me[2]NCH[2]CHOHCH[2)[n]][n+], and Magnafloc 1697, [(CH[2]CHCH[2]N(Me)[2]CH[2]CHCH[2])[n]][n+] have been shown to displace the exchangeable cation from the clay surface more effectively than other cationic species investigated such as Na[+], K[+], MeN[4+] and paraquat[2+]. This was shown through a decrease in linewidth and an increase in the [133]Cs or [23]Na NMR peak integral as cationic species were added to the clay. This information has been correlated with that obtained from particle size and zeta potential measurements in aqueous solution which suggest that the highly charged polycations investigated adsorb onto the surface of the clay via an 'electrostatic patch' mechanism. To complement these aqueous in situ techniques, several dry powder studies have been completed, including adsorption isotherms through Kjeldahl N analysis, variable temperature x-ray diffraction and thermogravimetric studies. These dry powder studies show conclusively that the exchangeable cation associated with the clay surface has a large bearing upon the amount and location of polymer adsorbed.The neutral polyglycol DCP101 is presently finding widespread use as a shale inhibitor in drilling muds. The mechanism by which this polymer interacts with clay has been investigated by recording the [133]Cs and [1]H NMR spectra of 25 gL[-1] suspensions of Cs[+] and Mn[2+] exchanged Westone-L treated with DCP101. These novel in situ investigations have shown that DCP101 does not displace the exchangeable cation associated with the clay. They have also shown that the water molecules in the hydration sphere of the Mn2+ cation associated with the clay surface are predominantly undisturbed by added DCP101. To complement these aqueous in situ investigations, several dry powder studies were carried out including adsorption isotherms through CHN analysis, variable temperature x-ray diffraction and thermogravimetric studies. These dry powder studies show that the exchangeable cation has a large bearing upon the quantity of polymer adsorbed.One further in situ NMR method has been evaluated with a view to investigating clay/polymer interactions. This method involved the addition of 10% D[2]O to a 40 gL[-1] suspension of clay which had been exchanged to the cation of interest. The resulting [2]H NMR spectrum showed a residual quadrupolar splitting, the magnitude of which depended upon several factors including clay concentration, state of aggregation of the clay platelets and the exchangeable cation associated with the clay. It was hoped that by monitoring the clay/D[2]O interactions via the [2]H residual quadrupolar splitting that information about clay/polymer systems in aqueous suspension would be forthcoming. The observed [2]H residual quadrupolar splitting was however found to be too sensitive to addition of polymer or ions to the clay suspension, resulting in its collapse to a singlet.