Effectiveness of poly(vinylpyridine) block copolymers as stabilizers of aqueous titanium dioxide dispersions of a high solid content

Diblock copolymers of 4-vinylpyridine (4VP) and sodium methacrylate (MANa) have been synthesized and tested as dispersants for aqueous dispersions (80 wt % solid) of alumina-coated titanium dioxide. P4VP is strongly anchored onto the pigment surface. The molecular composition of the block copolymers has an effect on the amount of copolymer required for imparting good stability to the slurry. Where the two parent triblock copolymers are concerned, triblocks consisting of PMANa outer blocks have a stabilizing efficiency comparable to the diblock copolymers, whereas the reverse structure is much less efficient. In the case of a nonblock distribution of 4VP and MANa in the copolymer chains, the stabilization effect is lost. Finally, the comparison of different stabilizing blocks attached to the same anchoring block confirms that the electrosteric stabilization mechanism is superior to the steric stabilization mechanism. A decrease in the anchoring strength of the diblocks has a deleterious effect on the dispersion stability.