INTERACTION BETWEEN POLY(N-VINYL-2-PYRROLIDONE) AND ANIONIC HYDROCARBON/FLUOROCARBON SURFACTANT ON HYDROPHOBIC GRAPHITE

The adsorption of poly(N-vinyl-2-pyrrolidone) (PVP), lithium dodecyl sulfate (LiDS), and lithium perfluorooctanesulfonate (LiFOS) from PVP-LiDS and PVP-LiFOS binary mixed solutions on hydrophobic graphite has been investigated by measuring the adsorbed amount, ESR spectra, and zeta potential. The adsorption of PVP is enhanced in the presence of LiDS at low LiDS concentration due to formation of a surface complex of PVP and LiDS, followed by a decrease at high LiDS concentration. However, this increment on hydrophobic graphite is significantly smaller than that on hydrophilic alumina. A similar trend is observed in the PVP-LiFOS system. In both PVP-LiDS and PVP-LiFOS systems, the conformation of PVP adsorbed is estimated using a spin-labeled PVP and is changed gradually from loops and tails to trains with the surfactant concentration. The fraction of train segments in the PVP-LiFOS system is greater than that in the PVP-LiDS system over the whole surfactant concentration region. (C) 1995 Academic Press, Inc.