The layer thickness of adsorbed nonionic surfactants: comparison between electrokinetic and film thickness methods

Stuart, M.A. Cohen; Boomgaard, Th. van den; Zourab, Sh.M.; Lyklema, J.

doi:10.1016/0166-6622(84)80155-9

Cited by 26 publications

(5 citation statements)

References 13 publications

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“…It is known that at low PVP concentrations the typical conformation of PVP chain molecules at the solid/aqueous solution interface consists of a sequence of many short loops and trains and at higher coverage the bound fraction decreases due to the formation of a relatively dense loop layer, with a few long tails protruding into the solution as mentioned above. Adsorbed layer thickness in the range 5−10 nm (plateau adsorption region) are known in the case of Pluronic F68, poly(ethylene oxide), nonylphenyl poly(propylene oxide)−poly(ethylene oxide) adducts and poly(vinylpyrrolidone), which is consistent with our results. Further, hydrodynamic thickness of adsorbed polymer layers has been calculated by Stuart et al .…”

Section: Resultssupporting

confidence: 92%

Simultaneous Adsorption of Poly(Vinylpyrrolidone) and Anionic Hydrocarbon/Fluorocarbon Surfactant from Their Binary Mixtures on Polystyrene Latex

Otsuka

Ring

et al. 1999

J. Phys. Chem. B

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Lithium dodecyl sulfate (LiDS)/lithium perfluorooctanesulfonate (LiFOS) and poly(vinylpyrrolidone) (PVP) were simultaneously adsorbed to polystyrene latex particles (PS) with diameter of 261 nm from PVP−LiDS and PVP−LiFOS binary mixed aqueous solutions. The conformation of PVP adsorbed on PS was estimated by using ESR. The thickness of the adsorbed layer was also determined by photon correlation spectroscopy (PCS) after pre-fractionation by sedimentation field-flow fractionation (sedFFF) which removed the aggregates and permitted an accurate PCS-based determination of the thickness of the coating layer. The adsorption of PVP was enhanced in the presence of LiDS at low LiDS concentrations owing to the formation of a surface complex of PVP and LiDS, followed by a decrease at high LiDS concentrations. A similar trend was observed in the PVP−LiFOS system. In both the PVP−LiDS and PVP−LiFOS systems, the conformation of PVP adsorbed was changed remarkably from loops and tails to trains with the surfactant concentration. The fraction of train segments in the PVP−LiFOS system was greater than that in the PVP−LiDS system, especially in the high surfactant concentration region. The thickness of PVP adsorbed on PS from the binary mixed solutions estimated from PCS decreased with an increase of the surfactant concentration. Thus, the ESR results were well correlated with the thickness of PVP adsorbed obtained from PCS.

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Section: Resultssupporting

confidence: 92%

Simultaneous Adsorption of Poly(Vinylpyrrolidone) and Anionic Hydrocarbon/Fluorocarbon Surfactant from Their Binary Mixtures on Polystyrene Latex

Otsuka

Ring

et al. 1999

J. Phys. Chem. B

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“…In a densely packed SAM, however, steric constraints prevent hydronium ions or cations from penetrating the SAM.] We therefore suggest an alternative explanation for the decrease of the electrokinetic potentials with increasing coverage, following the electrokinetic studies of Stuart et al on PEO-block-copolymers (streaming potential) 35,36 and of Cohen et al (electrophoretic mobility) 37 on liposomes grafted with PEG chains of similar (n ) 45) and higher chain length. Using Smoluchowski theory for the electrophoretic mobility, they observed for liposomes of identical surface charge a decreasing electrokinetic potential with increasing length of the grafted PEG chain.…”

Section: Discussionmentioning

confidence: 65%

“…Although there is convincing evidence for preferential cation binding within poly(ethylene oxide) gels, 32 the results obtained in the electrokinetic characterization of SAM-based OEG and PEG layers confirm charging through preferential adsorption of hydroxide anions for EG 3 OMe/Au surfaces, 19 while on the PEG SAMs the negative surface charge could also be caused by ion adsorption on uncovered segments of the underlying substrate. Differences in the electrokinetic charge in the PEG/Au systems as a function of coverage can be attributed to hydrodynamic effects without implying significant charging on the PEG chain itself, 18,[32][33][34][35] or alternatively to a decease in adsorbed hydroxide ion concentration due to reduced image charge stabilization with increasing film thickness. 33 We first discuss the negative charges caused by hydroxide adsorption on the OEG SAM surfaces, and then suggest models to explain the observations on the PEG surfaces.…”

Section: Discussionmentioning

confidence: 99%

Electrokinetic Characterization of Oligo- and Poly(ethylene glycol)-Terminated Self-Assembled Monolayers on Gold and Glass Surfaces

et al. 2003

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Force−distance studies suggest that electrostatic forces play a dominant role in the resistance of oligo(ethylene glycol) (OEG) terminated self-assembled monolayers (SAMs) to adsorption from aqueous solution, whereas for end grafted poly(ethylene glycol) (PEG) coated surfaces inertness is explained by a steric repulsion effect. To study the role of electrostatics in the repulsive forces measured on methoxytri(ethylene glycol) (EG3OMe) terminated alkanethiolate SAMs on gold surfaces, their electrokinetic potentials and charging properties were determined with the microslit electrokinetic setup (MES) using rectangular microchannels formed by SAM-covered sample carriers. The zeta potentials measured on the (EG3OMe) SAMs, both on gold and on glass substrate, indicate preferential hydroxide ion adsorption from the aqueous phase resulting in a net negative surface charge at pH >4. Calculated charge densities agree well with the results from force−distance studies. We also studied the electrokinetic properties of poly(ethylene glycol) (PEG) SAMs (HS(CH2)11(OCH2CH2)44−OCH3). All these films show a negative zeta potential in neutral and alkaline solutions which decreases with increasing packing density and optical film thickness, reflecting the changes in frictional properties of the PEG chains with increasing coverage. An explanation why the negatively charged (EG3OMe) surfaces exhibit repulsive electrostatic forces in aqueous solution, but other negatively charged surfaces do not, is proposed.

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“…24,26 Examples of good agreement between δ h (measured by PCS) and δ s (obtained by the surface forces apparatus) have been published, for both adsorbed homopolymers 27,28 and block copolymers. 22,29 Several issues regarding the relationship between the hydrodynamic adlayer thickness, adlayer structure, and the stability of colloids supporting such adlayers remain to be investigated. For example, while hydrodynamic thicknesses measured by PCS often accord with steric thicknesses determined by SFA measurements, studies showing such comparisons have not been accompanied with direct determinations of colloid stability, as might be quantified by determination of the stability ratio, W. Also, while it has been surmised that only a very low density of tails might be sufficient to confer steric stability, [30][31][32] experiments providing the minimum density for steric stability for any specific system have not been reported.…”

Section: Introductionmentioning

confidence: 99%

The Role of Long Tails in Steric Stabilization and Hydrodynamic Layer Thickness

Stenkamp

Berg

1997

Langmuir

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In steric stabilization, the "thickness" of the adsorbed layer on the particles is of key importance in determining the stability of the colloid. There is evidence to suggest that both the adlayer thickness, as measured by hydrodynamic means, and the colloid stability are determined solely by the most outwardextending tails in the adlayer, even when the tail density is quite low. The present study seeks to investigate experimentally and to quantify the relationship between tail density, hydrodynamic adlayer thickness and colloid stability for a model system consisting of a bimodal adlayer of triblock copolymers anchored to the surface of a latex colloid. The low molar mass component of the adlayer has a thickness too small to impart significant steric stability by itself, thereby isolating the stability attributable to the long tails provided by the high molar mass component. By systematic variation of the adlayer composition, the density of tails required to impart marginal stability can be determined and compared to the effect of tail density on the hydrodynamic thickness. For the system investigated, the adlayer proportion of long tails required for marginal stability was less than 0.5%, in good agreement with the proportion required to significantly increase the hydrodynamic adlayer thickness. The practical inference is that the most efficient steric stabilizers (on a per unit mass basis) are highly polydisperse mixtures with only a very small proportion of the highest molar mass constituent.

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The layer thickness of adsorbed nonionic surfactants: comparison between electrokinetic and film thickness methods

Cited by 26 publications

References 13 publications

Simultaneous Adsorption of Poly(Vinylpyrrolidone) and Anionic Hydrocarbon/Fluorocarbon Surfactant from Their Binary Mixtures on Polystyrene Latex

Simultaneous Adsorption of Poly(Vinylpyrrolidone) and Anionic Hydrocarbon/Fluorocarbon Surfactant from Their Binary Mixtures on Polystyrene Latex

Electrokinetic Characterization of Oligo- and Poly(ethylene glycol)-Terminated Self-Assembled Monolayers on Gold and Glass Surfaces

The Role of Long Tails in Steric Stabilization and Hydrodynamic Layer Thickness

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