Self‐assembled crystalline monolayers and multilayers of n‐alkanes on the water surface*

Weinbach, Susan P.; Weissbuch, Isabelle; Lahav, Meir; Leiserowitz, Leslie; Kjær, Kristian; Bouwman, Wim G.; Nielsen, Jens Als

doi:10.1002/adma.19950071009

Cited by 55 publications

(75 citation statements)

References 21 publications

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“…These very small crystals are generally unstable due to their high surface tension, and thus have a tendency to transform to larger particles by Oswald ripening. In recent years, quantum dots were prepared mainly in matrices and also as self-assembled structures, such as reverse micelles, [10] zeolites, [11] polymers, [12] self-assembled monolayers, [13] biopolymers, [14] layered metal phosphonates, [15] and Langmuir±Blodgett (LB) films. [16,17] In the preceding communication, [18] we reported that spreading of tetracosanedioic acid HOOC(CH 2 ) 22 COOH (C 24 diacid) on surfaces of aqueous solutions containing di- …”

Section: Methodsmentioning

confidence: 99%

“…Recently, the formation at the air±water interface of crystalline monolayer and multilayer films obtained from symmetric molecules with end groups equally hydrophobic or hydrophilic, such as long-chain linear fluorocarbons [14] and hydrocarbons, [15] oligothiophenes [16] (containing four, five, and six rings), and a,w-alkanediols, [17] has been reported. In these films at low surface pressure the long molecular axis is aligned either normal to the water surface or tilted by up to 40 from the normal.…”

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confidence: 99%

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Oriented Crystalline Thin Films of Tetracosanedioic Acid and Its Metal Salts at the Air-Aqueous Solution Interface

Weissbuch¹,

Guo

Edgar

et al. 1998

Adv. Mater.

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Langmuir monolayers are conventionally prepared by spreading, on a water surface, amphiphilic molecules containing hydrophilic head groups, which interact with the water molecules, and hydrophobic chains, which favor lateral aggregation in air. The crystalline packing of the molecules in the monolayer has been determined in situ, with almost atomic resolution by means of synchrotron X-ray diffraction using a monochromatic beam at grazing incidence.[1] With the use of this technique, the two-dimensional crystalline packing arrangement of monolayers of long-chain alcohols, [2±4] carboxylic acids, [5,6] amides, [7] aamino acids, [8±10] and phospholipids [11±13] could be determined. Recently, the formation at the air±water interface of crystalline monolayer and multilayer films obtained from symmetric molecules with end groups equally hydrophobic or hydrophilic, such as long-chain linear fluorocarbons [14] and hydrocarbons, [15] oligothiophenes [16] (containing four, five, and six rings), and a,w-alkanediols, [17] has been reported. In these films at low surface pressure the long molecular axis is aligned either normal to the water surface or tilted by up to 40 from the normal. Moreover, the formation of crystalline interdigitated trilayers from water-insoluble long-chain mandelic acid and phenylethylamine molecules contained in the subphase was proven by grazing incidence X-ray diffraction (GID).[18]The changes in packing arrangement of monolayers composed of long-chain carboxylic acids, as induced by the presence in the subphase of Cd 2+ , Ca 2+ , or Pb 2+ ions, have also been determined by GID. Over pure water and in the uncompressed state, the chains are tilted by approximately 30 from the normal to the water surface, whereas over solutions containing the metal ions, the chains are vertically aligned. [19,20] This report describes the self-assembly process of a,wtetracosanedioic acid, HOOC±(CH 2 ) 22 ±COOH, on aqueous subphases containing divalent Cd 2+ and Pb 2+ ions.These positive ions have a dramatic influence on the packing of the diacid molecules: they bind to both carboxylate ends of the molecule and force the long hydrocarbon chain to lie parallel to the water surface and to self-assemble as multilayer domains about 50 thick, but with the molecules and the bound ions perfectly ordered laterally over distances up to 1000 . GID and specular X-ray reflectivity (XR) were used to characterize the oriented crystalline multilayers of these cadmium and lead salts. Such multilayer films preserve their orientation during the transfer from the water surface onto a mica support, as imaged by scanning force microscopy (SFM), and can be used in the preparation of quantum dots (see following communication [21] ).The GID experiments were carried out at the synchrotron beamline BW1, HASYLAB, on the liquid surface diffractometer, as described elsewhere.[1] The samples were prepared by spreading solutions of the diacid onto pure water and onto aqueous subphases containing the metal ions, at 15 C, to give a nominal molecul...

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Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Oriented Crystalline Thin Films of Tetracosanedioic Acid and Its Metal Salts at the Air-Aqueous Solution Interface

Weissbuch¹,

Guo

Edgar

et al. 1998

Adv. Mater.

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“…These crystallites self-assemble spontaneously at zero surface pressure from excess material placed on water for 20 ϽnϽ30. 17,22 Mercury as a subphase for Langmuir films offers several additional advantages. The high surface energy of mercury, 500 mJ/m 2 , as compared to that of water, 72 mJ/m 2 , should enhance the spreading of surface films, and induce spreading in compounds not readily, or not at all, spreadable on water.…”

Section: Introductionmentioning

confidence: 99%

Langmuir films of normal-alkanes on the surface of liquid mercury

Kraack

Ocko

Pershan

et al. 2003

The Journal of Chemical Physics

141

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The Harvard community has made this article openly available. Please share how this access benefits you. Your story matters Citation Kraack, H., B. M. Ocko, Peter S. Pershan, E. Sloutskin, and M. Deutsch. 2003. Langmuir films of normal-alkanes on the surface of liquid mercury.The coverage dependent phase behavior of molecular films of n-alkanes (CH 3 CH nϪ2 CH 3 , denote Cn) on mercury was studied for lengths 10рnр50, using surface tensiometry and surface x-ray diffraction methods. In contrast with Langmuir films on water, where roughly surface-normal molecular orientation is invariably found, alkanes on mercury are always oriented surface-parallel, and show no long-range in-plane order at any surface pressure. At a low coverage a two-dimensional gas phase is found, followed, upon increasing the coverage, by a single condensed layer (n р18), a sequence of single and double layers (19рnр20; nу26), or a sequence of single, double, and triple layers (22рnр24). The thermodynamical and structural properties of these layers, as determined from the measurements, are discussed.

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“…12,23,24 For comparison we also study structural and dynamical water behavior at extended hydrophilic surfaces ͑macroscopic contact angle ls Ͻ10°). 19,42 Specifically, our present simulations include explicit TIP3 43 water molecules confined between the crystalline materials n-C 36 H 74 ͑hydrophobic͒ 19,44 and n-C 35 H 71 OH ͑hydrophilic͒. 45 The observed difference between water behavior in the two cases is discussed in the perspective of the hydrophobic effect.…”

Section: Introductionmentioning

confidence: 99%

The hydrophobic effect: Molecular dynamics simulations of water confined between extended hydrophobic and hydrophilic surfaces

Jensen

Mouritsen

Peters

2004

The Journal of Chemical Physics

103

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Structural and dynamic properties of water confined between two parallel, extended, either hydrophobic or hydrophilic crystalline surfaces of n-alkane C(36)H(74) or n-alcohol C(35)H(71)OH, are studied by molecular dynamics simulations. Electron density profiles, directly compared with corresponding experimental data from x-ray reflectivity measurements, reveal a uniform weak de-wetting characteristic for the extended hydrophobic surface, while the hydrophilic surface is weakly wetted. These microscopic data are consistent with macroscopic contact angle measurements. Specific water orientation is present at both surfaces. The ordering is characteristically different between the surfaces and of longer range at the hydrophilic surface. Furthermore, the dynamic properties of water are different at the two surfaces and different from the bulk behavior. In particular, at the hydrophobic surface, time-correlation functions reveal that water molecules have characteristic diffusive behavior and orientational ordering due to the lack of hydrogen bonding interactions with the surface. These observations suggest that the altered dynamical properties of water in contact with extended hydrophobic surfaces together with a partial drying of the surfaces are more indicative of the hydrophobic effect than structural ordering, which we suggest to be independent of surface topology.

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Self‐assembled crystalline monolayers and multilayers of n‐alkanes on the water surface*

Cited by 55 publications

References 21 publications

Oriented Crystalline Thin Films of Tetracosanedioic Acid and Its Metal Salts at the Air-Aqueous Solution Interface

Oriented Crystalline Thin Films of Tetracosanedioic Acid and Its Metal Salts at the Air-Aqueous Solution Interface

Langmuir films of normal-alkanes on the surface of liquid mercury

The hydrophobic effect: Molecular dynamics simulations of water confined between extended hydrophobic and hydrophilic surfaces

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