Complete and Partial Miscibility in Binary Monolayers of Phosphatidylethanolamines with Different Lengths of Acyl Groups

Doerfler, H.-D.; Koth, Chr; Rettig, W.

doi:10.1021/la00012a036

Cited by 10 publications

(6 citation statements)

References 2 publications

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“…Phase P 2 , consisting of monopalmitin molecules which, as a result of the LE−LC phase transition carried out at 14.5 mN/m, change their orientation from a horizontal position ( liquid−expanded state ) to a vertical position ( liquid−condensed state ) (Mp (v) ). This orientation change provokes their immiscibility with the horizontally oriented PMMA horizontally oriented, The incompatibility of the components due to their different orientation in the interface is often reported in the literature. − …”

Section: Discussionmentioning

confidence: 99%

Monolayer and Brewster Angle Microscopy Studies of Poly(methyl methacrylate)−Monopalmitin Mixed Systems at the Air−Water Interface

et al. 2010

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Mixed monolayers of poly(methyl metacrylate) (PMMA) and monopalmitin (Mp) were used for the study of their interactions. A thorough analysis of surface pressure (pi)-area (A) isotherms with the Langmuir monolayer technique, complemented with Brewster angle microscopy (BAM) images was performed. Mixed films show two phase transitions at a surface pressure of 14.5 mN/m and at 20-21 mN/m, respectively. Moreover, mixed monolayers show two well-defined collapses: one, corresponding to the lipid (at surface pressures of 50-51 mN/m) and the another one, ascribed to the PMMA, at surface pressure values of 57-58 mN/m. When the mean molecular areas of the mixed films (A(1,2)) were plotted versus film composition (X(1) or X(2)), positive deviations from the ideal behavior were observed at surface pressures below 15 mN/m, which were mainly attributed to a change in the conformation of the PMMA molecules at the surface. However, at higher surface pressures, the areas per monomer unit of the mixed monolayers obey the additivity rule, attributed to the fact that the film components form an immiscible system in these conditions.

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Section: Discussionmentioning

confidence: 99%

Monolayer and Brewster Angle Microscopy Studies of Poly(methyl methacrylate)−Monopalmitin Mixed Systems at the Air−Water Interface

et al. 2010

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“…Thus, the results of Niccolai et al, related to mixed monolayers of 1-glycerol monooleoil (MON) and 1-glycerol monoestearoil (MOS), confirm the “empirical rule” that immiscibility of the components at the interface is due to their different orientations (MON, horizontal; MOS, vertical). Other authors , attribute the miscibility or immiscibility of the components to the physical state of their respective monolayers: when both are in the same surface state (for example in the expanded state), components are miscible at the interface, whereas if they are in different surface states (for example, liquid-expanded and liquid-condensed states), they are partially miscible or immiscible. In fact, this reference to the physical states of the monolayer is another way of considering the different orientations of the molecules at the interface, because the nature of the surface state depends on the arrangement of molecules on the water surface.…”

Section: Discussionmentioning

confidence: 99%

Interactions between Polymers and Lipid Monolayers at the Air/Water Interface: Surface Behavior of Poly(methyl methacrylate)−Cholesterol Mixed Films

Conde

Trillo

et al. 2010

J. Phys. Chem. B

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The behavior of mixed monolayers of cholesterol and poly(methyl methacrylate) (PMMA) with molecular weights of M(w) = 120,000 g/mol and M(w) = 15,000 g/mol was investigated at the air/water interface using Langmuir and Brewster angle microscopy techniques. From the data of surface pressure (pi)-area (A) isotherms, compressional modulus-surface pressure (C(s)(-1)-pi) curves, and film thickness, complemented with Brewster angle microscopy images, the interaction between the components was analyzed. Regardless of the surface pressure (pi = 10, 20, or 30 mN/m) at which the mean molecular/monomer areas (Am) were calculated, the Am-mole fraction plots (corresponding to X(PMMA) = 0.1, 0.3, 0.5, 0.7, and 0.9) show that all the experimental points obtained are placed on the theoretical straight line calculated according to the additivity rule. This fact, together with the existence of two collapses in the mixed monolayers and with the fact that the surface pressure of the liquid-expanded LE-L'E phase transition of PMMA does not change with the monolayer composition, demonstrates the immiscibility of the film components at the interface. The application of the Crisp phase rule to the phase diagram of PMMA-cholesterol mixed monolayers helps to explain the existence of a biphasic system, regardless of their composition and surface pressure. Besides, Brewster angle microscopy (BAM) images showed the existence of heterogeneous cholesterol domains with high reflectivity immersed in a homogeneous polymer separate phase with low reflectivity.

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“…The thermodynamic parameters, namely the limiting area per molecule, the compression modulus, and the collapse surface pressure, obtained from compression isotherms give important information on the monolayer characterization. The mean molecular area is the most common and sensitive parameter to give confirmatory and complementary information on the packing of the hydrocarbon chains in certain “monolayer states”. , The packing of the chains is governed by the balance between cohesive forces, thermal agitation, and the affinity between hydrophilic groups and water molecules. On the other hand, the collapse pressures give definitive proof of the insolubility of components in surface mixtures.…”

Section: Discussionmentioning

confidence: 99%

Mixed Monolayers of Heptadecanoic Acid with Chlorohexadecane and Bromohexadecane. Effects of Temperature and of Metal Ions in the Subphase

Silva¹,

Guerreiro²,

Rodrigues³

et al. 1996

Langmuir

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Mixed monomolecular films of heptadecanoic acid (HpA)−chlorohexadecane (ClHx) and heptadecanoic acid−bromohexadecane (BrHx) at the air/water interface were studied on ultrapure water and on aqueous substrates containing cadmium sulfate and barium chloride at 15 and 25 °C. The surface pressure−area (π−A) isotherms were determined by the Wilhelmy plate method. ClHx and BrHx by themselves do not form insoluble monolayers at the air/water interface. The shape of the mixed isotherms varies with the composition, the temperature, and the presence of metal ions in the subphase. For many compositions, the alkyl halide is partially squeezed out of the monolayer before the final collapse. It was observed that this initial collapse of the mixed monolayer decreases with the mole fraction of the alkyl halide and with temperature and varies with the halogen atom in the guest molecule: BrHx is preferred on the pure water subphase while, in the presence of Cd2+, ClHx is preferred. The presence of Cd2+ in the subphase promotes a condensing effect of the mixed monolayers, decreases the initial collapse surface pressure, and induces a second collapse in the two mixtures studied for a mole fraction of alkyl halide x 2 > 0.3. The condensing effect of Cd2+ is more pronounced in the system with chloride than in the presence of bromine. On the basis of monolayer collapse surface pressures and mean molecular areas, the two-dimensional miscibility was investigated. The range of miscibility decreases with the surface pressure and with the temperature.

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Complete and Partial Miscibility in Binary Monolayers of Phosphatidylethanolamines with Different Lengths of Acyl Groups

Cited by 10 publications

References 2 publications

Monolayer and Brewster Angle Microscopy Studies of Poly(methyl methacrylate)−Monopalmitin Mixed Systems at the Air−Water Interface

Monolayer and Brewster Angle Microscopy Studies of Poly(methyl methacrylate)−Monopalmitin Mixed Systems at the Air−Water Interface

Interactions between Polymers and Lipid Monolayers at the Air/Water Interface: Surface Behavior of Poly(methyl methacrylate)−Cholesterol Mixed Films

Mixed Monolayers of Heptadecanoic Acid with Chlorohexadecane and Bromohexadecane. Effects of Temperature and of Metal Ions in the Subphase

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