The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Milton J. Rosen - One of the best experts on this subject based on the ideXlab platform.
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ultralow interfacial tension for enhanced oil recovery at very low surfactant concentrations
Langmuir, 2005Co-Authors: Milton J. Rosen, Hongzhuang Wang, Pingping Shen, Youyi ZhuAbstract:The interfacial tension (IFT) between alkanes and several individual surfactants and their mixtures has been investigated, using three kinds of alkyl hydrocarbons: decane, dodecane, and tetradecane. For individual and mixed surfactant systems, critical micelle concentrations and areas per molecule at the hydrocarbon−aqueous Solution Interface were calculated; for the mixed surfactant systems, , the molecular interaction parameter at the hydrocarbon−aqueous Solution Interface, and βM, the molecular interaction parameter in mixed micelle formation, were calculated. It was found that IFT in the 10-3 mN/m (ultralow) range can be obtained at surfactant concentrations below 0.05 wt % and even at concentrations below 0.01 wt %, when mixtures of certain surfactants are used at the proper ratio. Surfactants with branched-chain alkyl groups show a much better IFT reduction effectiveness than those with straight-chain alkyl groups. Contrary to what has been observed at the air−aqueous Solution surface, mixtures of ...
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molecular interactions of surfactants in mixed monolayers at the air aqueous Solution Interface and in mixed micelles in aqueous media the regular Solution approach
Langmuir, 2003Co-Authors: Qiong Zhou And, Milton J. RosenAbstract:Experimental area/molecule data (Aexpt) at the air/aqueous Solution Interface after mixing, ideal mixing area/molecule data (Aideal), based upon area/molecule data at that Interface before mixing, and regular Solution theory have been used to explain the values of surfactant molecular interaction (β) parameters observed in mixed monolayers and mixed micelles. The value of the β parameter reflects the difference in surfactant−surfactant interactions before and after mixing. In ionic−nonionic surfactant mixtures, when surfactant−surfactant interactions are weak, reduction in electrostatic self-repulsion interaction energy of the ionic surfactant, due to the dilution effect upon mixing, is suggested as a major contributor to the negative β values observed for mixed monolayers and mixed micelles. Steric effects appear when surfactant molecular structure varies in the size of the headgroups and in the branching of the hydrophobic groups. It is suggested that the effect of an increase in the size of the hydroph...
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superspreading of trisiloxane surfactant mixtures on hydrophobic surfaces 2 interaction and spreading of aqueous trisiloxane surfactant n alkyl pyrrolidinone mixtures in contact with polyethylene
Langmuir, 2002Co-Authors: Milton J. RosenAbstract:On the basis of the results of interfacial adsorptions of an ethoxylated trsiloxane(L77) and its mixtures with various N-alkyl-pyrrolidinones, the changes in interfacial pressure at the air/aqueous Solution, polyethylene/aqueous Solution, and air/polyethylene Interfaces caused by the surfactant mixture Solutions have been evaluated by use of the Gibbs equation. At the air/aqueous Solution Interface, the change in the surface tension, (ΔγLA), is always positive, indicating that there is no effect that could enhance spreading at this Interface upon the addition of N-alkyl-pyrrolidinones to the trisiloxane surfactant Solution. At the polyethylene/aqueous Solution Interface, the change in interfacial pressure, (ΔπSL), can be positive when N-alkyl-pyrrolidinones are mixed at a certain ratio, indicating that the mixtures can show a spreading enhancement effect at this Interface. Compared with the changes at the air/aqueous Solution Interface and the polyethylene/aqueous Solution Interface, the change in interfa...
Alberto E Regazzoni - One of the best experts on this subject based on the ideXlab platform.
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surface complexation at the tio2 anatase aqueous Solution Interface chemisorption of catechol
Journal of Colloid and Interface Science, 1996Co-Authors: Raul Rodriguez, Miguel A Blesa, Alberto E RegazzoniAbstract:Abstract Catechol adsorbs at the TiO2(anatase)/aqueous Solution Interface forming inner-sphere surface complexes. The UV–visible differential reflectance spectrum of surface titanium–catecholate complexes presents a band centered at 420 nm which corresponds to the ligand to metal charge transfer transition within the surface complexes. At pH values below pKa1, the surface excess of catechol is almost insensitive toward pH and presents a Langmuirian dependence with the concentration of uncomplexed catechol. The ratio Γmax:NS(NSbeing the measured density of available OH surface groups) indicates a prevailing 1 to 2 ligand exchange adsorption stoichiometry. In the range pH ≥ pKa1, the catechol surface excess decreases markedly with increasing pH. Formation of 1 to 1 surface complexes produces an excess of negative surface charge that is revealed by the shift of the iep to lower pH values. The reported data, which are supplemented with information on the charging behavior of TiO2suspended in indifferent electrolyte Solutions, are interpreted in terms of the multi-site surface complexation model. In this model, two types of surface OH groups are considered: ≡TiOH1/3−and ≡OH1/3+. Although both surface groups undergo protonation–deprotonation reactions, only ≡TiOH1/3−are prone to chemisorption.
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surface complexation at the tio2 anatase aqueous Solution Interface chemisorption of catechol
Journal of Colloid and Interface Science, 1996Co-Authors: Raul Rodriguez, Miguel A Blesa, Alberto E RegazzoniAbstract:Catechol adsorbs at the TiO(2) (anatase)/aqueous Solution Interface forming inner-sphere surface complexes. The UV-visible differential reflectance spectrum of surface titanium-catecholate complexes presents a band centered at 420 nm which corresponds to the ligand to metal charge transfer transition within the surface complexes. At pH values below pK(a1), the surface excess of catechol is almost insensitive toward pH and presents a Langmuirian dependence with the concentration of uncomplexed catechol. The ratio Gamma(max):N(S) (N(S) being the measured density of available OH surface groups) indicates a prevailing 1 to 2 ligand exchange adsorption stoichiometry. In the range pH >/= pK(a1), the catechol surface excess decreases markedly with increasing pH. Formation of 1 to 1 surface complexes produces an excess of negative surface charge that is revealed by the shift of the iep to lower pH values. The reported data, which are supplemented with information on the charging behavior of TiO(2) suspended in indifferent electrolyte Solutions, are interpreted in terms of the multi-site surface complexation model. In this model, two types of surface OH groups are considered: identical withTiOH(1/3-) and identical withOH(1/3+). Although both surface groups undergo protonation-deprotonation reactions, only identical withTiOH(1/3-) are prone to chemisorption.
R. K. Thomas - One of the best experts on this subject based on the ideXlab platform.
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the impact of electrolyte on the adsorption of the anionic surfactant methyl ester sulfonate at the air Solution Interface surface multilayer formation
Journal of Colloid and Interface Science, 2018Co-Authors: Hai Xu, R J L Welbourne, Peixun Li, Jeff Penfold, R. K. Thomas, David W. Roberts, Jordan T. PetkovAbstract:Abstract The methyl ester sulfonates represent a promising group of anionic surfactants which have the potential for improved performance and biocompatibility in a range of applications. Their Solution properties, in particular their tolerance to hard water, suggests that surface ordering may occur in the presence of multi-valent counterion. Understanding their adsorption properties in a range of different circumstances is key to the exploitation of their potential. Neutron reflectivity and surface tension have been used to characterise the adsorption at the air-aqueous Solution Interface of the anionic surfactant sodium tetradecanoic 2-sulfo 1-methyl ester, C14MES, in the absence of electrolyte and in the presence of mono, di, and tri-valent counterions, Na+, Ca2+, and Al3+. In particular the emphasis has been on exploring the tendency to form layered structures at the Interface. In the absence of electrolyte and in the presence of NaCl and CaCl2 and AlCl3 at low concentrations monolayer adsorption is observed, and the addition of electrolyte results in enhanced adsorption. In the presence of NaCl and CaCl2 only monolayer adsorption is observed. However at higher AlCl3 concentrations surface multilayer formation is observed, in which the number of bilayers at the surface depends upon the surfactant and AlCl3 concentrations.
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multilayering of surfactant systems at the air dilute aqueous Solution Interface
Langmuir, 2015Co-Authors: R. K. Thomas, J PenfoldAbstract:In the last 15 years there have been a number of observations of surfactants adsorbed at the air–water Interface with structures more complicated than the expected single monolayer. These observations, mostly made by neutron or X-ray reflectivity, show structures varying from the usual monolayer to monolayer plus one or two additional bilayers to multilayer adsorption at the surface. These observations have been assembled in this article with a view to finding some common features between the very different systems and to relating them to aspects of the bulk Solution phase behavior. It is argued that multilayering is primarily associated with wetting or prewetting of the air–water Interface by phases in the bulk system, whose structures depend on an overall attractive force between the constituent units. Two such phases, whose formation is assumed to be partially driven by strong specific ion binding, are a concentrated lamellar phase that forms at low concentrations and a swollen lamellar phase that is n...
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the impact of alkyl sulfate surfactant geometry and electrolyte on the co adsorption of anionic surfactants with model perfumes at the air Solution Interface
Journal of Colloid and Interface Science, 2013Co-Authors: Robert Bradbury, Jeff Penfold, R. K. Thomas, Jordan T. Petkov, I Tucker, Craig JonesAbstract:The impact of surfactant geometry and electrolyte on the co-adsorption of anionic surfactants and model perfumes at the air-Solution Interface has been studied by neutron reflectivity. The more hydrophobic perfume linalool, competes more favourably for the surface with sodium dodecylsulfate than was previously reported for the anionic surfactant, sodium dodecyl 6-benzenesulfonate. Due to an increase in surface activity of the sodium dodecylsulfate, the addition of electrolyte results in a reduction in the linalool adsorption. Changing the alkyl chain length affects the relative adsorption of linalool and surfactant at the Interface. Similar measurements for the different alkyl sulfates and with electrolyte with the more hydrophilic perfume phenyl ethanol, reveal broadly similar trends. Although the relative adsorption of phenyl ethanol with sodium dodecylsulfate is substantially enhanced compared to sodium dodecyl-6-benzenesulfonate the effects are not as significant as was observed with linalool. The variations with alkyl chain geometry show the importance of the hydrophobic interaction between the perfume and surfactant and changes in the packing constraints on the relative adsorption. The results highlight the importance of the specific interaction between the surfactant and perfume, and the surfactant and perfume geometries on the relative adsorption at the Interface.
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adsorption of model perfumes at the air Solution Interface by coadsorption with an anionic surfactant
Langmuir, 2013Co-Authors: Robert Bradbury, R. K. Thomas, Jordan T. Petkov, I Tucker, J Penfold, Craig JonesAbstract:The adsorption of the model perfumes phenyl ethanol, PE, and linalool, LL, at the air–Solution Interface by coadsorption with the anionic surfactant sodium dodecyl 6-benezene sulfonate, LAS-6, has been studied primarily by neutron reflectivity, NR. The variation in the mixed surface adsorption with Solution composition is highly nonideal, and the more hydrophobic LL is more surface active. At a LAS-6 concentration of 0.5 mM the adsorption of PE and LL is broadly similar but with the LL systematically more surface active, and at 2 mM the LL completes more effectively for the surface than the PE. The variation in surface composition with Solution composition and concentration reflect the greater hydrophobicity and hence surface activity of LL, and the greater solubility of PE in aqueous Solution. Changing the geometry of the LAS isomer, from the symmetrical LAS-6 geometry to the more asymmetrical LAS-4, results in the LL competing more effectively for the surface due to changes in the packing constraints as...
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effect of architecture on the formation of surface multilayer structures at the air Solution Interface from mixtures of surfactant with small poly ethyleneimine s
Langmuir, 2012Co-Authors: Silvia Halacheva, R. K. Thomas, J Penfold, John R P WebsterAbstract:The impact of ethyleneimine architecture on the adsorption behavior of mixtures of small poly(ethyleneimines) and oligoethyleneimines (OEIs) with the anionic surfactant sodium dodecylsulfate (SDS) at the air–Solution Interface has been studied by surface tension (ST) and neutron reflectivity (NR). The strong surface interaction between OEI and SDS gives rise to complex surface tension behavior that has a pronounced pH dependence. The NR data provide more direct access to the surface structure and show that the patterns of ST behavior are correlated with substantial OEI/SDS adsorption and the spontaneous formation of surface multilayer structures. The regions of surface multilayer formation depend upon SDS and OEI concentrations, on the Solution pH, and on the OEI architecture, linear or branched. For the linear OEIs (octaethyleneimine, linear poly(ethyleneimine) or LPEI8, and decaethyleneimine, LPEI10) with SDS, surface multilayer formation occurs over a range of OEI and SDS concentrations at pH 7 and to ...
J Penfold - One of the best experts on this subject based on the ideXlab platform.
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multilayering of surfactant systems at the air dilute aqueous Solution Interface
Langmuir, 2015Co-Authors: R. K. Thomas, J PenfoldAbstract:In the last 15 years there have been a number of observations of surfactants adsorbed at the air–water Interface with structures more complicated than the expected single monolayer. These observations, mostly made by neutron or X-ray reflectivity, show structures varying from the usual monolayer to monolayer plus one or two additional bilayers to multilayer adsorption at the surface. These observations have been assembled in this article with a view to finding some common features between the very different systems and to relating them to aspects of the bulk Solution phase behavior. It is argued that multilayering is primarily associated with wetting or prewetting of the air–water Interface by phases in the bulk system, whose structures depend on an overall attractive force between the constituent units. Two such phases, whose formation is assumed to be partially driven by strong specific ion binding, are a concentrated lamellar phase that forms at low concentrations and a swollen lamellar phase that is n...
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adsorption of model perfumes at the air Solution Interface by coadsorption with an anionic surfactant
Langmuir, 2013Co-Authors: Robert Bradbury, R. K. Thomas, Jordan T. Petkov, I Tucker, J Penfold, Craig JonesAbstract:The adsorption of the model perfumes phenyl ethanol, PE, and linalool, LL, at the air–Solution Interface by coadsorption with the anionic surfactant sodium dodecyl 6-benezene sulfonate, LAS-6, has been studied primarily by neutron reflectivity, NR. The variation in the mixed surface adsorption with Solution composition is highly nonideal, and the more hydrophobic LL is more surface active. At a LAS-6 concentration of 0.5 mM the adsorption of PE and LL is broadly similar but with the LL systematically more surface active, and at 2 mM the LL completes more effectively for the surface than the PE. The variation in surface composition with Solution composition and concentration reflect the greater hydrophobicity and hence surface activity of LL, and the greater solubility of PE in aqueous Solution. Changing the geometry of the LAS isomer, from the symmetrical LAS-6 geometry to the more asymmetrical LAS-4, results in the LL competing more effectively for the surface due to changes in the packing constraints as...
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effect of architecture on the formation of surface multilayer structures at the air Solution Interface from mixtures of surfactant with small poly ethyleneimine s
Langmuir, 2012Co-Authors: Silvia Halacheva, R. K. Thomas, J Penfold, John R P WebsterAbstract:The impact of ethyleneimine architecture on the adsorption behavior of mixtures of small poly(ethyleneimines) and oligoethyleneimines (OEIs) with the anionic surfactant sodium dodecylsulfate (SDS) at the air–Solution Interface has been studied by surface tension (ST) and neutron reflectivity (NR). The strong surface interaction between OEI and SDS gives rise to complex surface tension behavior that has a pronounced pH dependence. The NR data provide more direct access to the surface structure and show that the patterns of ST behavior are correlated with substantial OEI/SDS adsorption and the spontaneous formation of surface multilayer structures. The regions of surface multilayer formation depend upon SDS and OEI concentrations, on the Solution pH, and on the OEI architecture, linear or branched. For the linear OEIs (octaethyleneimine, linear poly(ethyleneimine) or LPEI8, and decaethyleneimine, LPEI10) with SDS, surface multilayer formation occurs over a range of OEI and SDS concentrations at pH 7 and to ...
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adsorption behavior of hydrophobin and hydrophobin surfactant mixtures at the solid Solution Interface
Langmuir, 2011Co-Authors: X L Zhang, R. K. Thomas, Jordan T. Petkov, I Tucker, J Penfold, Julian Bent, Andrew Richard CoxAbstract:The adsorption of surface-active protein hydrophobin, HFBII, and HFBII/surfactant mixtures at the solid-Solution Interface has been studied by neutron reflectivity, NR. At the hydrophilic silicon surface, HFBII adsorbs reversibly in the form of a bilayer at the Interface. HFBII adsorption dominates the coadsorption of HFBII with cationic and anionic surfactants hexadecyltrimethyl ammonium bromide, CTAB, and sodium dodecyl sulfate, SDS, at concentrations below the critical micellar concentration, cmc, of conventional cosurfactants. For surfactant concentrations above the cmc, HFBII/surfactant Solution complex formation dominates and there is little HFBII adsorption. Above the cmc, CTAB replaces HFBII at the Interface, but for SDS, there is no affinity for the anionic silicon surface hence there is no resultant adsorption. HFBII adsorbs onto a hydrophobic surface (established by an octadecyl trimethyl silane, OTS, layer on silicon) irreversibly as a monolayer, similar to what is observed at the air-water Interface but with a different orientation at the Interface. Below the cmc, SDS and CTAB have little impact upon the adsorbed layer of HFBII. For concentrations above the cmc, conventional surfactants (CTAB and SDS) displace most of the HFBII at the Interface. For nonionic surfactant C(12)E(6), the pattern of adsorption is slightly different, and although some coadsorption at the Interface takes place, C(12)E(6) has little impact on the HFBII adsorption.
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polyelectrolyte surfactant mixtures at the air Solution Interface
Current Opinion in Colloid and Interface Science, 2006Co-Authors: J Penfold, R. K. Thomas, D J F TaylorAbstract:Abstract This review presents some of the recent developments in our understanding of the behaviour of polyelectrolyte/surfactant mixtures at the air–Solution Interface. The existence of a strong surface polyelectrolyte/surfactant interaction results in a complex pattern of surface adsorption. Recent studies, using a range of surface sensitive techniques, which include ellipsometry, neutron and X-ray reflectivity, surface tension and interfacial rheology, have considerably enhanced the understanding of their surface behaviour, which can be rationalized in terms of the competition between the formation of surface active polymer/surfactant complexes and Solution polymer/surfactant micelle complexes.
Raul Rodriguez - One of the best experts on this subject based on the ideXlab platform.
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surface complexation at the tio2 anatase aqueous Solution Interface chemisorption of catechol
Journal of Colloid and Interface Science, 1996Co-Authors: Raul Rodriguez, Miguel A Blesa, Alberto E RegazzoniAbstract:Abstract Catechol adsorbs at the TiO2(anatase)/aqueous Solution Interface forming inner-sphere surface complexes. The UV–visible differential reflectance spectrum of surface titanium–catecholate complexes presents a band centered at 420 nm which corresponds to the ligand to metal charge transfer transition within the surface complexes. At pH values below pKa1, the surface excess of catechol is almost insensitive toward pH and presents a Langmuirian dependence with the concentration of uncomplexed catechol. The ratio Γmax:NS(NSbeing the measured density of available OH surface groups) indicates a prevailing 1 to 2 ligand exchange adsorption stoichiometry. In the range pH ≥ pKa1, the catechol surface excess decreases markedly with increasing pH. Formation of 1 to 1 surface complexes produces an excess of negative surface charge that is revealed by the shift of the iep to lower pH values. The reported data, which are supplemented with information on the charging behavior of TiO2suspended in indifferent electrolyte Solutions, are interpreted in terms of the multi-site surface complexation model. In this model, two types of surface OH groups are considered: ≡TiOH1/3−and ≡OH1/3+. Although both surface groups undergo protonation–deprotonation reactions, only ≡TiOH1/3−are prone to chemisorption.
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surface complexation at the tio2 anatase aqueous Solution Interface chemisorption of catechol
Journal of Colloid and Interface Science, 1996Co-Authors: Raul Rodriguez, Miguel A Blesa, Alberto E RegazzoniAbstract:Catechol adsorbs at the TiO(2) (anatase)/aqueous Solution Interface forming inner-sphere surface complexes. The UV-visible differential reflectance spectrum of surface titanium-catecholate complexes presents a band centered at 420 nm which corresponds to the ligand to metal charge transfer transition within the surface complexes. At pH values below pK(a1), the surface excess of catechol is almost insensitive toward pH and presents a Langmuirian dependence with the concentration of uncomplexed catechol. The ratio Gamma(max):N(S) (N(S) being the measured density of available OH surface groups) indicates a prevailing 1 to 2 ligand exchange adsorption stoichiometry. In the range pH >/= pK(a1), the catechol surface excess decreases markedly with increasing pH. Formation of 1 to 1 surface complexes produces an excess of negative surface charge that is revealed by the shift of the iep to lower pH values. The reported data, which are supplemented with information on the charging behavior of TiO(2) suspended in indifferent electrolyte Solutions, are interpreted in terms of the multi-site surface complexation model. In this model, two types of surface OH groups are considered: identical withTiOH(1/3-) and identical withOH(1/3+). Although both surface groups undergo protonation-deprotonation reactions, only identical withTiOH(1/3-) are prone to chemisorption.
