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Jeffrey Penfold - One of the best experts on this subject based on the ideXlab platform.
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Adsorption at the Air-water interface in Biosurfactant-Surfactant mixtures: Quantitative Analysis of Adsorption in a Five Component Mixture
Langmuir : the ACS journal of surfaces and colloids, 2017Co-Authors: Jessica R. Liley, Jeffrey Penfold, Ian M. Tucker, Robert Thomas, Jordan T. Petkov, Paul Stevenson, Ibrahim M. Banat, Roger Marchant, Michelle Rudden, John R P WebsterAbstract:The composition of the air–water adsorbed layer of a quinary mixture consisting of three conventional surfactants, Octaethylene Glycol monododecyl ether (C12E8), dodecane-6-p-sodium benzene sulfonate (LAS6), and diethylene Glycol monododecyl ether sodium sulfate (SLE2S), mixed with two biosurfactants, the rhamnolipids l-rhamnosyl-l-rhamnosyl-β-hydroxydecanoyl-β-hydroxydecanoyl, R2, and l-rhamnosyl-β-hydroxydecanoyl-β-hydroxydecanoyl, R1, has been measured over a range of compositions above the mixed critical micelle concentration. Additional measurements on some of the subsets of ternary and binary mixtures have also been measured by NR. The results have been analyzed using the pseudophase approximation (PPA) in conjunction with an excess free energy, GE, that depends on the quadratic and cubic terms in the composition. The compositions of the binary, ternary, and quinary mixtures could all be fitted to two sets of interaction parameters between the pairs of surfactants, one for micelles and one for adsor...
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Adsorption of nonionic surfactant mixtures at the hydrophilic solid-solution interface.
Langmuir : the ACS journal of surfaces and colloids, 2005Co-Authors: Jeffrey Penfold, I. Tucker, Robert K. ThomasAbstract:The adsorption of the mixed nonionic surfactants, monododecyl triethylene Glycol (C12EO3) and monododecyl Octaethylene Glycol (C12EO8), at the hydrophilic silica−solution interface has been studied by specular neutron reflectivity. The adsorption at the solid−solution interface is compared with that previously measured at the air−solution interface. The marked differences that are observed are explained in terms of the different packing constraints or preferred curvature arising from the disparity in the respective headgroup dimensions.
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The structure of mixed nonionic surfactant monolayers at the air-water interface: the effects of different alkyl chain lengths.
Journal of colloid and interface science, 2003Co-Authors: Jeffrey Penfold, Ian M. Tucker, Robert Thomas, E. Staples, R Woodling, Chuchuan DongAbstract:Abstract The structure of mixed nonionic surfactant monolayers of monodecyl hexaethylene Glycol (C10E6) and monotetradecyl hexaethylene Glycol (C14E6) adsorbed at the air–water interface has been determined by specular neutron reflectivity. Using partial isotopic labeling (deuterium for hydrogen) of the alkyl and ethylene oxide chains of each surfactant, the distribution and relative positions of the chains at the interface have been obtained. The packing of the two different alkyl chain lengths results in structural changes compared to the pure surfactant monolayers. This results in changes in the relative positions of the alkyl chains and of the ethylene oxide chains at the interface. The role of the alkyl chain length is contrasted with that of the ethylene oxide chain length, determined from results reported previously on the nonionic surfactant mixture of monododecyl triethylene Glycol (C12E3) and monododecyl Octaethylene Glycol (C12E8) (J. Penfold, et al., J. Colloid Interface Sci. 201 (1998) 223).
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Solvent distribution in non-ionic surfactant monolayers
Physical Chemistry Chemical Physics, 2002Co-Authors: Jeffrey Penfold, Robert K. ThomasAbstract:The distribution of solvent in the adsorbed monolayers of the non-ionic surfactants monododecyl hexaethylene Glycol, C12E6, and monododecyl Octaethylene Glycol, C12E8, at the air–water interface has been determined from specular neutron reflectivity measurements. The data is analysed by the method of partial structure factors, and the solvent distribution is described by a new approach that improves previous estimates based on a tanh profile. An improved description and quantification of hydration in surface adsorbed layers is required for the further development of the thermodynamic treatment of surfactant mixing at interfaces. It is a term currently neglected in theories based on the pseudo phase approximation. However, the comparison of some recent neutron reflectivity results and surface tension data for mixed surfactants suggests that its contribution may be important.
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The structure of mixed surfactants at the air–water interface
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1999Co-Authors: Jeffrey Penfold, E. Staples, I. Tucker, Robert ThomasAbstract:Abstract The structure of the mixed non-ionic surfactant monolayer of monododecyl triethylene Glycol (C12E3) and monododecyl Octaethylene Glycol (C12E8) and of the mixed cationic–non-ionic surfactant monolayer of hexadecytrimethyl ammonium bromide (C16TAB) and monododcyl hexaethylene Glycol (C12E6) adsorbed at the air–water interface are described. For the non-ionic surfactant mixture the frustration caused by packing the triethylene and Octaethylene Glycol headgroups results in a change of the surfactant structure compared to the pure monolayer of either surfactant. In particular the Octaethylene Glycol group is less extended, and the alkyl chain conformation is altered. Although the structures of the cationic and non-ionic surfactants in the non-ionic–cationic surfactant mixture are similar to those of the pure monolayers at an equivalent area per molecule, the detailed labelling schemes used reveal some changes. In the mixed monolayer the alkyl chains of both surfactants are more extended, and the amount of overlap between the surfactant and solvent distributions is greater. The structure of the C16TAB/C12E6 mixture is contrasted with previously published results for the mixtures sodium dodecyl sulphate (SDS)-dodecanol and dodecyl trimethylammonium bromide (C12TAB)-dodecane, which show an increasing change in position of the non-ionic additive at the interface relative to the solvent distribution with increasing solubility of the non-ionic component.
Robert Thomas - One of the best experts on this subject based on the ideXlab platform.
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Adsorption at the Air-water interface in Biosurfactant-Surfactant mixtures: Quantitative Analysis of Adsorption in a Five Component Mixture
Langmuir : the ACS journal of surfaces and colloids, 2017Co-Authors: Jessica R. Liley, Jeffrey Penfold, Ian M. Tucker, Robert Thomas, Jordan T. Petkov, Paul Stevenson, Ibrahim M. Banat, Roger Marchant, Michelle Rudden, John R P WebsterAbstract:The composition of the air–water adsorbed layer of a quinary mixture consisting of three conventional surfactants, Octaethylene Glycol monododecyl ether (C12E8), dodecane-6-p-sodium benzene sulfonate (LAS6), and diethylene Glycol monododecyl ether sodium sulfate (SLE2S), mixed with two biosurfactants, the rhamnolipids l-rhamnosyl-l-rhamnosyl-β-hydroxydecanoyl-β-hydroxydecanoyl, R2, and l-rhamnosyl-β-hydroxydecanoyl-β-hydroxydecanoyl, R1, has been measured over a range of compositions above the mixed critical micelle concentration. Additional measurements on some of the subsets of ternary and binary mixtures have also been measured by NR. The results have been analyzed using the pseudophase approximation (PPA) in conjunction with an excess free energy, GE, that depends on the quadratic and cubic terms in the composition. The compositions of the binary, ternary, and quinary mixtures could all be fitted to two sets of interaction parameters between the pairs of surfactants, one for micelles and one for adsor...
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The structure of mixed nonionic surfactant monolayers at the air-water interface: the effects of different alkyl chain lengths.
Journal of colloid and interface science, 2003Co-Authors: Jeffrey Penfold, Ian M. Tucker, Robert Thomas, E. Staples, R Woodling, Chuchuan DongAbstract:Abstract The structure of mixed nonionic surfactant monolayers of monodecyl hexaethylene Glycol (C10E6) and monotetradecyl hexaethylene Glycol (C14E6) adsorbed at the air–water interface has been determined by specular neutron reflectivity. Using partial isotopic labeling (deuterium for hydrogen) of the alkyl and ethylene oxide chains of each surfactant, the distribution and relative positions of the chains at the interface have been obtained. The packing of the two different alkyl chain lengths results in structural changes compared to the pure surfactant monolayers. This results in changes in the relative positions of the alkyl chains and of the ethylene oxide chains at the interface. The role of the alkyl chain length is contrasted with that of the ethylene oxide chain length, determined from results reported previously on the nonionic surfactant mixture of monododecyl triethylene Glycol (C12E3) and monododecyl Octaethylene Glycol (C12E8) (J. Penfold, et al., J. Colloid Interface Sci. 201 (1998) 223).
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The structure of mixed surfactants at the air–water interface
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1999Co-Authors: Jeffrey Penfold, E. Staples, I. Tucker, Robert ThomasAbstract:Abstract The structure of the mixed non-ionic surfactant monolayer of monododecyl triethylene Glycol (C12E3) and monododecyl Octaethylene Glycol (C12E8) and of the mixed cationic–non-ionic surfactant monolayer of hexadecytrimethyl ammonium bromide (C16TAB) and monododcyl hexaethylene Glycol (C12E6) adsorbed at the air–water interface are described. For the non-ionic surfactant mixture the frustration caused by packing the triethylene and Octaethylene Glycol headgroups results in a change of the surfactant structure compared to the pure monolayer of either surfactant. In particular the Octaethylene Glycol group is less extended, and the alkyl chain conformation is altered. Although the structures of the cationic and non-ionic surfactants in the non-ionic–cationic surfactant mixture are similar to those of the pure monolayers at an equivalent area per molecule, the detailed labelling schemes used reveal some changes. In the mixed monolayer the alkyl chains of both surfactants are more extended, and the amount of overlap between the surfactant and solvent distributions is greater. The structure of the C16TAB/C12E6 mixture is contrasted with previously published results for the mixtures sodium dodecyl sulphate (SDS)-dodecanol and dodecyl trimethylammonium bromide (C12TAB)-dodecane, which show an increasing change in position of the non-ionic additive at the interface relative to the solvent distribution with increasing solubility of the non-ionic component.
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The Structure of the Mixed Nonionic Surfactant Monolayer of Monododecyl Triethylene Glycol and Monododecyl Octaethylene Glycol at the Air–Water Interface
Journal of Colloid and Interface Science, 1998Co-Authors: Jeffrey Penfold, E. Staples, Ian M. Tucker, Robert ThomasAbstract:Abstract The structure of the mixed nonionic surfactant monolayer of monododecyl triethylene Glycol and monododecyl Octaethylene Glycol adsorbed at the air–water interface has been determined using specular neutron reflection. Using partial isotopic labeling (deuterium/hydrogen) of the alkyl and ethylene oxide chains of each type of molecule, the distribution and relative positions of those labeled fragments have been obtained. The frustration caused by the packing of the triethylene and Octaethylene Glycol headgroups results in a change of the surfactant structure compared to the pure monolayer of either surfactant. Compared to the pure monolayer the alkyl chain distributions of both surfactants are more extended, the triethylene Glycol group is less hydrated, and the Octaethylene Glycol group is less extended and more hydrated.
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Neutron Reflection from a Layer of Monododecyl Octaethylene Glycol Adsorbed at the Air-Liquid Interface: The Structure of the Layer and the Effects of Temperature
The Journal of Physical Chemistry, 1994Co-Authors: Robert Thomas, E. Staples, L. J. Thompson, I. Tucker, Jeffrey PenfoldAbstract:We have determined the structure of a monolayer of monododecyl Octaethylene Glycol (C12E8) adsorbed at the air/water interface at its critical micelle concentration and at temperatures of 298 and 323 K using neutron specular reflection in combination with isotopic labeling. There is little effect of temperature on the coverage of the pure material, though a significant variation is observed when the material was slightly contaminated with lower members of the series (C12Em with m < 8). However, subtle changes in the structure of the adsorbed layer do occur, the alkyl chain region becoming about 14% thicker at the higher temperature, whereas the thickness of the ethylene Glycol chain region does not change. An analysis of these differences and the changes in the separation of the different fragments of the surfactant suggest that the layer is increasingly roughened at the higher temperature and that the ethylene Glycol chain region is significantly dehydrated. The structure of C12E8 is compared with other members of the C12Em series at approximately the same area per molecule of 55-65 Å2. The alkyl chain thickness is constant throughout the series, and the values of the structural parameters indicate a large average tilt of the surfactant molecules away from the surface normal and a significant incidence of gauche conformations in the alkyl chain. © 1994 American Chemical Society
Takashi Kakiuchi - One of the best experts on this subject based on the ideXlab platform.
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successive complex formation of multivalent ions with Octaethylene Glycol dodecyl ether at the nitrobenzene water interface
Journal of Electroanalytical Chemistry, 1993Co-Authors: Takashi KakiuchiAbstract:Transfer of Mg2+ and La3+ ions across the nitrobenzene (NB)/water (W) interface facilitated by Octaethylene Glycol monododecyl ether (C12E8) has been studied using cyclic voltammetry under conditions where the concentration of C12E8 in NB(bcC12E8NB) is much smaller than the concentration of Mg2+ or La3+ ions in W. The shape of the voltammograms is markedly dependent on bcC12E8NB. When bcC12E8NB⩾ 1 mM, the voltammograms exhibit a clear shoulder on both forward and reverse scans of the potential. For La3+ transfer, the convolution voltammograms exhibit two-step waves. The dependence of wave shape on ligand concentration indicates the successive formation of 1:2 (metal:ligand) and 1:1 complexes in the vicinity of the interface. The first wave is ascribed to the formation of the 1:2 (metal:ligand) complex, and the second wave to the 1:1 complex. This double wave merges into a single peak, when bcC12E8NB
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Successive complex formation of multivalent ions with Octaethylene Glycol dodecyl ether at the nitrobenzene/water interface
Journal of Electroanalytical Chemistry, 1993Co-Authors: Takashi KakiuchiAbstract:Transfer of Mg2+ and La3+ ions across the nitrobenzene (NB)/water (W) interface facilitated by Octaethylene Glycol monododecyl ether (C12E8) has been studied using cyclic voltammetry under conditions where the concentration of C12E8 in NB(bcC12E8NB) is much smaller than the concentration of Mg2+ or La3+ ions in W. The shape of the voltammograms is markedly dependent on bcC12E8NB. When bcC12E8NB⩾ 1 mM, the voltammograms exhibit a clear shoulder on both forward and reverse scans of the potential. For La3+ transfer, the convolution voltammograms exhibit two-step waves. The dependence of wave shape on ligand concentration indicates the successive formation of 1:2 (metal:ligand) and 1:1 complexes in the vicinity of the interface. The first wave is ascribed to the formation of the 1:2 (metal:ligand) complex, and the second wave to the 1:1 complex. This double wave merges into a single peak, when bcC12E8NB
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Mechanism of the transfer of alkali- and alkaline-earth-metal ions across the nitrobenzene-water interface facilitated by hexa- and Octaethylene Glycol dodecyl ethers
Journal of Colloid and Interface Science, 1993Co-Authors: Takashi KakiuchiAbstract:Abstract Transfer of Li + , Na + , K + , Rb + ,Ca 2+ , Sr 2+ , and B a2+ ions facilitated by hexa- and Octaethylene Glycol monododecyl ethers (C12E6 and C12E8) has been studied at the nitrobenzene (NB)-water (W) interface using cyclic voltammetry. When the concentration of C12E n ( n = 6 or 8) in NB is higher than 1 mM, cyclic voltammograms for all these ions show reversible transfer of ions facilitated by C12E n . The current is mainly carried by 1:1 (metal:ligand) complex and is limited by the diffusion of C12E n in N B. When the concentration of C12E n in NB is lowered to the submillimolar range, the contribution of the adsorption of C12E n to the current becomes significant. In the transfer of hydrophilic ions, e.g., Li + and Ca 2+ , the contribution of the complex with 1:2 (metal:ligand) stoichiometry to the measured current becomes nonnegligible. This 1:2 complex formation becomes pronounced with increasing ligand concentration.
Victor Starov - One of the best experts on this subject based on the ideXlab platform.
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Kinetics of spreading of synergetic surfactant mixtures in the case of partial wetting
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2016Co-Authors: Nina Kovalchuk, Faiz M. Mahdi, Anna Trybala, Victor StarovAbstract:Spreading kinetics of mixtures of hydrocarbon surfactant, Octaethylene Glycol monododecyl ether, and fluoro-surfactant, Zonyl FSN-100, on highly hydrophobic substrate was experimentally studied. The mixtures reveal a synergism in their wetting properties with equilibrium contact angle of mixtures being 15–20° lower than that of individual surfactant solutions. The synergism is due to different affinity of the surfactants to the liquid/air and liquid/solid interface. Both individual surfactants and their mixtures demonstrate power law kinetics of spreading over the time span of tens of seconds. The spreading exponent is lower than that for pure liquids, but spreading exponent of mixtures is higher than that of individual solutions. The maximum in the spreading exponent is observed for the mixtures demonstrating the lowest equilibrium contact angles. For these mixtures the spreading exponent is close to that of pure liquids.
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Kinetics of spreading of synergetic surfactant mixtures in the case of partial wetting
2016Co-Authors: Nina Kovalchuk, Faiz M. Mahdi, Victor Starov, Anna TrybalaAbstract:© 2015 Elsevier B.V.Spreading kinetics of mixtures of hydrocarbon surfactant, Octaethylene Glycol monododecyl ether, and fluoro-surfactant, Zonyl FSN-100, on highly hydrophobic substrate was experimentally studied. The mixtures reveal a synergism in their wetting properties with equilibrium contact angle of mixtures being 15–20° lower than that of individual surfactant solutions. The synergism is due to different affinity of the surfactants to the liquid/air and liquid/solid interface. Both individual surfactants and their mixtures demonstrate power law kinetics of spreading over the time span of tens of seconds. The spreading exponent is lower than that for pure liquids, but spreading exponent of mixtures is higher than that of individual solutions. The maximum in the spreading exponent is observed for the mixtures demonstrating the lowest equilibrium contact angles. For these mixtures the spreading exponent is close to that of pure liquids
Albert Zilkha - One of the best experts on this subject based on the ideXlab platform.
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Non‐bond crosslinked macroporous thermally reversible hydrogels
Polymers for Advanced Technologies, 2007Co-Authors: Yair Avny, Anat Zada, Albert ZilkhaAbstract:Non-bond crosslinked macroporous thermally reversible hydrogels of poly-N-isopropylacrylamide were obtained by copolymerization with the crosslinking agent cyclic Octaethylene Glycol fumarate, a 29-membered ring, having a polymerizable double bond; threading of polymer chains into the macrocyclic ring being the cause for the crosslinking. These hydrogels showed a high swelling capacity in water which could be controlled by varying the molar ratio of monomer/crosslinking agent. They rapidly ‘collapsed’ at 33° and swelled back at low temperatures. Copyright © 2007 John Wiley & Sons, Ltd.
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Non-bond crosslinked polymer hydrogels
European Polymer Journal, 2001Co-Authors: Albert ZilkhaAbstract:Non-bond crosslinked polymer hydrogels of N-vinyl pyrrolidone were obtained by copolymerization with the cross linking agent cyclic Octaethylene Glycol fumarate, a 29-membered ring, having a polymerizable double bond. Threading of polymer chains into the macrocyclic rings is the cause for the crosslinking. These hydrogels showed a high swelling capacity in water, which could be controlled either by varying the molar ratio of monomer/crosslinking agent or through copolymerization with different concentrations of hydrophobic monomers.
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Monomers for non-bond crosslinking of vinyl polymers: II. Cyclic Octaethylene Glycol 5-methacrylamido-isophthalate☆
European Polymer Journal, 2000Co-Authors: Anat Zada, Yair Avny, Albert ZilkhaAbstract:The new concept of non-bond crosslinking of vinyl polymers is demonstrated with cyclic Octaethylene Glycol 5-methacrylamido-isophthalate, which was synthesized and copolymerized with methyl methacrylate to yield insoluble copolymers with a high swelling capacity, threading of polymer chains through the rings being the cause of the crosslinking. Evidence for the threading was obtained from 2D nuclear magnetic resonance.
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Monomers for non-bond crosslinking of vinyl polymers
European Polymer Journal, 1999Co-Authors: Anat Zada, Yair Avny, Albert ZilkhaAbstract:Abstract Monomers having on the one hand a polymerizable double bond and on the other hand a large macrocyclic ring (n≥27–28) through which a growing chain may be threaded are shown to be a new type of crosslinking agents which lead to non-bond crosslinking of vinyl polymers. This is demonstrated by cyclic Octaethylene Glycol fumarate, a 29-membered ring obtained in the reaction of fumaryl chloride with Octaethylene Glycol under high dilution conditions, which upon copolymerization with styrene or methylmethacrylate led to crosslinked polymers.