Simultaneous adsorption of sodium dodecyl sulfate and poly(vinyl pyrrolidone) on titanium dioxide with quaternary ammonium groups

Simultaneous adsorption of sodium dodecyl sulfate (SDS) and poly(vinyl pyrrolidone) (PVP) on titanium dioxide with quaternary ammonium groups (XNm, where m is the carbon number of the alkyl chain, 8 and 12) was investigated by measuring the amount of adsorbed SDS and PVP, zeta potential, and dispersion stability. The conformation of PVP adsorbed was also estimated using a spin-labeled polymer. The amount of SDS adsorbed on XNm in the presence of PVP was enhanced at low SDS concentrations, but was depressed at high SDS concentrations compared with that in the absence of PVP. Further, the amounts of SDS adsorbed on XNm in the presence and in the absence of PVP were greater than that on untreated titanium dioxide. The adsorption of PVP was remarkably enhanced at low SDS concentrations, followed by a dramatic decrease at high SDS concentrations for XNm and untreated titanium dioxide. The results of ESR measurements indicate that the PVP adsorbed on XNm in the absence and in the presence of SDS takes mainly train conformation, while the PVP adsorbed on untreated titanium dioxide in the absence of SDS takes loops or tails and converts to train conformation in the presence of SDS. In addition, the dispersion stability of XNm and untreated titanium dioxide suspensions increased at low SDS concentrations in the presence of PVP compared to that in the absence of PVP. (C) 1999 Elsevier Science B.V. All rights reserved.