Observation of bond orientational order in floating and transferred monolayers with Brewster angle microscopy

Overbeck, Gernot A.; Hönig, Dirk; Wolthaus, L.; Gnade, Michael; Möbius, Dietmar

doi:10.1016/0040-6090(94)90496-0

Cited by 40 publications

(25 citation statements)

References 13 publications

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“…The dependence of R on d 2 (eq 1) can be used to determine the relative thickness of film regions even if the optical properties of the film are unknown . Although this approach is sufficient for the work reported here, a further step to calculate values of the monolayer thickness based on a model for the observed morphology has been used recently. − However, for our purpose the exact film thickness is not as interesting as the question of monolayer or multilayer formation depending on the experimental conditions.…”

Section: Methodsmentioning

confidence: 99%

Morphological and Structural Characteristics of Monoglyceride Monolayers at the Air−Water Interface Observed by Brewster Angle Microscopy

1999

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In this paper we report the morphology of monolayer domains for some typical lipids used as food emulsifiers (monopalmitin, monoolein, and monolaurin). In addition, we propound the utility of BAM for quantitative characterization of the relative film thickness as a function of the lipid and surface density. The surface pressure (π)−area isotherms and the Brewster angle microscopy (BAM) images of monopalmitin, monoolein, and monolaurin monolayers spread on buffered water at pH 7 and at 20 °C indicate that the morphology and structural characteristics of these lipids are very dependent on the hydrocarbon chain length and the presence of a double bond in the hydrocarbon chain. With a camera calibration it is possible to determine the relationship between the gray level and the relative reflectivity. The relative reflectivity allows the determination of the relative thickness of the monolayer. The present studies show the utility of a master curve of relative reflectivity versus surface pressure that is characteristic for any lipid. The results of the relative thickness measurements show that the monolayer thickness increases with the surface pressure and is maximum at the collapse point. The monolayer thickness is higher for monopalmitin monolayers and lower for monoolein monolayers. The thickness of the monolaurin film is halfway between those for monopalmitin and monoolein monolayers. The higher monolayer thickness correlates with the higher long-range lipid−lipid interactions and with closer molecular packing at the air−water interface.

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Section: Methodsmentioning

confidence: 99%

Morphological and Structural Characteristics of Monoglyceride Monolayers at the Air−Water Interface Observed by Brewster Angle Microscopy

1999

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“…With the development of Brewster angle microscopy (BAM), , a sensitive and effective method is available for studying the organization in spread monolayers at the air−water interface at the microscopic level. BAM provides information on the morphology of amphiphilic monolayers, − including the inner structure of condensed domains and phase transitions in monolayers, − the orientational order of the monolayer domains, ,, deformation − and relaxation phenomena 23,26-28 in monolayer domains caused by compression−expansion cycles or by interfacial flow, and so forth. Recently, this technique has been applied to the analysis of the morphology in adsorption layers of one- , and two-component systems. , As the light intensity at each point in the BAM image depends on the local thickness and monolayer optical properties, this technique can be used to determine the thickness of film regions, even when the optical properties of the film (refractive index) are unknown, if a model for the observed morphology is adopted. ,− …”

Section: Introductionmentioning

confidence: 99%

Is Brewster Angle Microscopy a Useful Technique To Distinguish between Isotropic Domains in β-Casein− Monoolein Mixed Monolayers at the Air−Water Interface?

1999

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The surface pressure (π)−area (A) isotherms and Brewster angle microscopy (BAM) images of monoolein−β-casein mixed films spread on buffered water at pH 5 and 7 and at 20 °C were determined as a function of the mass fraction of monoolein in the mixture (X). The structural characteristics, miscibility, and morphology of monoolein−β-casein mixed films were very dependent on surface pressure and monolayer composition. The structure in monoolein−β-casein mixed monolayers was liquid-expanded-like, as for pure components. The monolayer structure was more expanded as the pH and the monoolein concentration in the mixture were increased. From the concentration and surface pressure dependence on excess area, elasticity, and collapse pressure it was deduced that monoolein and β-casein form a practically immiscible monolayer at the air−water interface. The BAM images and the evolution with the surface pressure of the relative reflectivity of BAM images give complementary information on the interactions and structural characteristics of monoolein−β-casein mixed monolayers, which corroborated the conclusions derived from the π−A isotherm. The morphology of monoolein, β-casein, and monoolein−β-casein domains at surface pressures lower than that for β-casein collapse cannot be observed by BAM due to the fact that pure components and mixed monolayers form isotropic domains at the air−water interface. However, the high relative reflectivity of β-casein domains after the collapse point leads to the conclusion that monoolein was unable to displace totally the protein from the mixed monolayer at the air−water interface, even at higher monoolein concentrations in the mixture and at higher surface pressures.

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“…Firstorder phase transitions can be visualized in this way. Moreover, with an analyzer placed in the path of the reflected light, optical anisotropies due to the molecular tilt [20,21] or to the unit-cell anisotropy in untilted phases [20,22] can be detected. On the images, each shade of gray corresponds either to a different tilt-azimuthal orientation of the molecules in the tilted phases or to a different orientation of the unit cell in the untilted phase.…”

mentioning

confidence: 99%

Observation of a two-step mechanism in the formation of a superstructure of cadmium-behenic acid Langmuir monolayer: Evidence of an intermediate structure

et al. 2004

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By means of grazing incidence x-ray diffraction, the structure of a behenic acid monolayer spread over chloride salt solutions of cadmium is observed to evolve from the tilted L2 phase to the superstructure (corresponding to an organized monolayer of ions in addition to the ordered organic film), through an intermediate phase. The studied salt concentrations are below the so-called "threshold" needed for the formation of this superstructure. This kinetic process involving two first-order phase transitions is confirmed by Brewster angle microscopy experiments and surface pressure-area isotherms measured at different times after monolayer deposition.

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Observation of bond orientational order in floating and transferred monolayers with Brewster angle microscopy

Cited by 40 publications

References 13 publications

Morphological and Structural Characteristics of Monoglyceride Monolayers at the Air−Water Interface Observed by Brewster Angle Microscopy

Morphological and Structural Characteristics of Monoglyceride Monolayers at the Air−Water Interface Observed by Brewster Angle Microscopy

Is Brewster Angle Microscopy a Useful Technique To Distinguish between Isotropic Domains in β-Casein− Monoolein Mixed Monolayers at the Air−Water Interface?

Observation of a two-step mechanism in the formation of a superstructure of cadmium-behenic acid Langmuir monolayer: Evidence of an intermediate structure

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