Abstract
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 ζ 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.
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