Control of the stability of silica dispersion with the aid of charged diblockcopolymers

The influence of adsorption layers of nonselectively soluble diblockcopolym ers, including charged blocks of poly(dimethylaminoethyl methacrylate) and neutral blocks of dihydroxypropyl methacrylate on the electrokinetic proper ties and the stability of silicon dioxide dispersions, was studied. It was shown that at a diblockcopolymer concentration in a system equal to 25-50 m g/l, adsorption layers 10-12 nm thick are formed at the particle surfaces. Further increases in the polymer concentration at pH 8.5-9.5 resulted in a dramatic increase in adsorption layer thickness, whereas at pH 10.2 the thi ckness remains unchanged. Electrokinetic potential decreased (in some cases , nonmonotonically) when diblockcopolymer concentration varied from 0 to 10 0 mg/l; however, the reversal of the particle charge did not occur. It was shown that these diblockcopolymers can either decrease of increase (in the presence of displacing agents) the stability of silica dispersion. These re gularities were discussed, and assumptions on the mechanism of the influenc e of diblockcopolymers on the stability of silica dispersions were made.