SIMULTANEOUS ADSORPTION OF POLY(VINYLPYRROLIDONE) AND CATIONIC SURFACTANT FROM THEIR MIXED-SOLUTIONS ON SILICA

The adsorption of poly(vinylpyrrolidone) (PVP) and dodecyltrimethylammonium chloride (DTAC) on silica has been investigated as a function of DTAC concentration. The adsorption of PVP decreases gradually with increasing DTAC concentration, whereas the adsorption of DTAC increases, but the magnitude of the increase in the adsorption is smaller than that in the absence of PVP. The colloid stability of the silica dispersion is poor at low concentrations of PVP, but is enhanced at higher concentrations of PVP. Electron spin resonance measurements indicate that the conformation of adsorbed PVP is relatively flat at low concentrations of PVP, while the conformation becomes more extended at higher concentrations. The stability of the silica dispersion is thus well correlated with the change in the conformation of PVP adsorbed.