Neutron reflectivity studies of adsorption and wetting in the vicinity of a liquid/liquid critical point: alkane + perfluoroalkane mixtures at a silicon interface

Bowers, James; Manzanares-Papayanopoulos, Emilio; McLure, Ian A.; Cubitt, R.

doi:10.1088/0953-8984/10/37/006

Cited by 10 publications

(18 citation statements)

References 33 publications

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“…A different geometry that would enable us to follow the development of density profiles and interfacial fluctuations to thick films, and thus to bulk behavior, would be to lower a horizontal substrate below the surface of the bulk mixture. Measurements performed in this way could be compared with previous ellipsometry, [17][18][19]40 evanescentwave-generated fluorescence spectroscopy, 20 neutron, 55,56 and x-ray scattering experiments 42,61 on PF/MC and related mixtures.…”

Section: Discussionmentioning

confidence: 99%

Quenching of capillary waves in composite wetting films from a binary vapor: An x-ray reflectivity study

2001

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We report x-ray reflectivity measurements of the internal structure of thin wetting films formed on a silicon substrate from the vapor of a binary mixture of methylcyclohexane ͑MC͒ and perfluoromethylcyclohexane ͑PF͒. At Tϭ30°C ͑below the bulk consolute temperature of T c Ϸ46°C) variation in the difference in temperature between the substrate and the vapor induces changes in film thickness ͑25 to 135 Å) that are consistent with complete wetting of both surfaces, with a MC-rich phase wetting the substrate and a PF-rich phase wetting the free surface. The width of the internal liquid/liquid interface, however, is found to be noticeably smaller than values predicted from the convolution of the intrinsic interfacial profile between bulk liquids with the capillary wave roughness as modified by dispersion interactions with the substrate. The difference is attributed to the effects of confinement. Although the width of the liquid/liquid interface is less well defined above the consolute point (Tϭ60°C), we still find PF enrichment at the free surface and MC enrichment at the substrate.

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Section: Discussionmentioning

confidence: 99%

Quenching of capillary waves in composite wetting films from a binary vapor: An x-ray reflectivity study

2001

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“…The nature of its adsorption at the free liquid and silicaceous interfaces has been studied previously. 14,16,17 The hexane-h 14 ϩperfluorohexane mixtures are complemented, where appropriate, by isotopically related mixtures incorporating perdeutero-n-hexane ͑hexane-d 14 ). Hexane ͑Aldrich, 99 ϩ%͒, hexane-d 14 ͑Goss Scientific Ltd., 99ϩD at.…”

Section: A Choice Of System and Preparation Of Liquid Mixturesmentioning

confidence: 99%

Adsorption from alkane+perfluoroalkane mixtures at fluorophobic and fluorophilic surfaces. I. Nature of the noncritical adsorption profiles

Bowers

Zarbakhsh

Christenson

et al. 2003

The Journal of Chemical Physics

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Local structure of a phase-separating binary mixture in a mesoporous glass matrix studied by small-angle neutron scattering Adsorption from alkane+perfluoroalkane mixtures at fluorophobic and fluorophilic surfaces. II. Crossover from critical adsorption to complete wetting Neutron reflection has been applied to probe the nature and extent of adsorption from a mixture of (1Ϫx)n-hexaneϩx perfluoro-n-hexane against silicon substrates modified with alkylsilane ͑fluorophobic͒ or fluoroalkylsilane ͑fluorophilic͒ coupled layers. For an equimolar mixture (x ϭ0.5, 60.7 vol %͒ in the one-phase region at Tϭ30°C-removed both in temperature and composition from the upper critical point at 22.65°C and xϭ0.36-the structure was resolved at both fluorophobic and fluorophilic surfaces. Liquid mixtures with three different refractive index contrasts were used to reduce model ambiguity in the ensuing analysis. For both surfaces the composition profiles of the adsorbed liquids could be represented using two-layer slab models which included interlayer Gaussian roughness. For the fluorophobic surface, the thickness of the layer closest to the substrate is ϳ20 Å and composed of ϳ83 vol % n-hexane, and the second, more dilute layer has a composition profile which decays smoothly into the bulk over a range of ϳ100 Å. A similar result is found for the fluorophilic surface, but in this case the layer closest to the substrate is ϳ15 Å thick and composed of ϳ95 vol % perfluoro-n-hexane. Qualitatively similar behavior is found for adsorption from a mixture with xϭ0.7 against a fluorophobic substrate and for a mixture with xϭ0.2 against a fluorophilic substrate.

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“…7 The substrates were then chemically dried prior to treatment with a silane coupling agent octadecyltrichlorosilane (ACROS, 95%) using established methods. 8 This has been shown to provide a chemically bound hydrophobic layer on the silica surface. 9 In our previous work, we have characterized this layer by measuring the reflectivity from the Si-water interface using a series of contrasts.…”

Section: Methodsmentioning

confidence: 99%

“…Neutron reflectivity is a technique sensitive to the average neutron refractive index, n, profile normal to an interface. 8 The dispersive refractive index can be written as…”

Section: Methodsmentioning

confidence: 99%

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Structural Studies of Aliphatic Substituted Phthalocyanine−Lipid Multilayers

et al. 2010

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A Langmuir-Blodgett film of aliphatic substituted phthalocyanines on a C18 silane supporting layer coupled onto a 11 silicon substrate has been investigated using neutron reflectometry. This multilayer structure is seen as a possible The focus of our project was to study the structure and hence ) and lipid 59 multilayer structures on a hydrophobic solid support using 60 neutron reflectometry technique. We seek to determine the water 61 content of the phthalocyanine multilayers, as this plays an impor-

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Neutron reflectivity studies of adsorption and wetting in the vicinity of a liquid/liquid critical point: alkane + perfluoroalkane mixtures at a silicon interface

Cited by 10 publications

References 33 publications

Quenching of capillary waves in composite wetting films from a binary vapor: An x-ray reflectivity study

Quenching of capillary waves in composite wetting films from a binary vapor: An x-ray reflectivity study

Adsorption from alkane+perfluoroalkane mixtures at fluorophobic and fluorophilic surfaces. I. Nature of the noncritical adsorption profiles

Structural Studies of Aliphatic Substituted Phthalocyanine−Lipid Multilayers

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