Freeze-fracture electron microscopy study of mesophases in mixtures of polyoxyethylene (14) oleylether and water

Jousma, H.; Bouwstra, Joke A.; Spies, F.; Junginger, Hans E.

doi:10.1007/bf01418460

Cited by 20 publications

(9 citation statements)

References 29 publications

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“…In other words, the polydomain lamellar microstructure is formed by connected liquid crystalline monodomains with random orientation so that from a macroscopic point of view it looks disoriented and with structural defects (Barnes, 1980). The technique of freeze-fracture transmission electron microscopy provides clear pictures supporting the microstructure above described Kopp, 1987 and, (Jousma et al, 1987).…”

Section: Structure Of Lamellar Liquid Crystals (L α α )mentioning

confidence: 63%

Rheological and phase behaviour of amphiphilic lipids

Muñoz

Alfaro

2000

Grasas y Aceites

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RESUMEN Comportamiento reológico y de fase de lípidos anfifílicosEn este capítulo se realiza una revisión de las distintas estructuras coloidales de asociación que pueden formar los lípidos anfifílicos en estado líquido-cristalino y de sus correspondientes propiedades de flujo en cizalla. Se describe la estructura y comportamiento reológico de cristales líquidos termotrópicos, con énfasis en los de tipo esméctico, fases gel, y cristales líquidos liotrópicos: nemáticos, laminares, laminares diluidos, dispersiones de laminares, hexagonales y cúbicos. Se hace hincapié en la importancia de una buena caracterización reológica y reo-óptica de cara a sus aplicaciones prácticas, desarrollo de formulaciones y como una técnica útil para determinar diagramas de fases y detectar cambios de estructura. Se ha usado una metodología histórica para analizar la evolución de la caracterización reológica e identificación de las diferentes estructuras líquido-cristalinas y estructuras afines. La interpretación de comportamientos de flujo viscoso no newtonianos, fenómenos tixotrópicos y antitixotrópicos y de las propiedades viscoelásticas lineales, determinadas con ensayos dinámicos y de fluencia, y no lineales, descritas mediante la diferencia de esfuerzos normales y ensayos de relajación del esfuerzo, se basa en la interrelación microestructuracomportamiento reológico. La naturaleza policristalina de los cristales líquidos resulta ser muy sensible a la cizalla, debido al cambio de tamaño y orientación de los dominios líquido-cristalinos mientras fluyen. PALABRAS-CLAVE: Comportamiento de fase Comportamiento reológico Lípidos anfifílicos. SUMMARY Rheological and phase behaviour of amphiphilic lipidsThis chapter reviews the different association structures which are likely to be formed by amphiphilic lipids in the liquid-crystalline state and their corresponding shear flow properties. The structure and rheological behaviour of thermotropic liquid crystals, emphasizing the properties of smectic mesophases, and those of lyotropic liquid crystals such as: nematic, lamellar, diluted lamellar, lamellar dispersions, hexagonal and cubic mesophases are described. The importance of a comprehensive rheological characterisation, including rheo-optical techniques, is pointed out for their practical applications, development of formulations and as a useful technique to assist in the determination of phase diagrams. A historical approach has been used to discuss the evolving field of the rheology and structure identification of liquid crystals formed by amphiphilic lipids and surfactants. Non-Newtonian viscous shear flow, thixotropic and antithixotropic phenomena, linear viscoelastic properties -described by dynamic and creep compliance experiments-and non-linear viscoelastic properties -described by the difference of normal stresses and stress relaxation tests are interpreted on the basis of a microstructure-rheology relationship. The polycrystalline nature of liquid crystals turns out to be rather sensitive to shear due to the change of both size...

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Section: Structure Of Lamellar Liquid Crystals (L α α )mentioning

confidence: 63%

Rheological and phase behaviour of amphiphilic lipids

Muñoz

Alfaro

2000

Grasas y Aceites

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“…10a, b). Also, sometimes textures with parallel lines were seen, resembling fracture faces of Ha [40]. The directly observed repeat spacing (do) from SAXD for this sample is 14 nm.…”

Section: Structure Of the Gel-phasementioning

confidence: 68%

“…Studying I1, formed in mixtures of water and polyoxyethylene (14)oleyl ether, by using FFEM, layers with spherical units in a hexagonal array were seen [40]. Using the same procedures, such fracture faces could also be found on replicas of gel-phase samples.…”

Section: Structure Of the Gel-phasementioning

confidence: 90%

Changes of mesophase structure of BRIJ 96/water mixtures on addition of liquid paraffin

Jousma

Joosten

Gooris

et al. 1989

Colloid & Polymer Sci

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The influence of the addition of liquid paraffin (LP) on the structure of the lamellar (L~) and hexagonal (H1) mesophases formed in mixtures of water (W) and BRIJ 96 (/3) was studied. Mesophases were identified using polarization microscopy and small angle x-ray diffraction (SAXD). Repeat spacings were also determined with SAXD. Depending on the W/B ratio, addtion of LP to L~ gives a large, almost linear one-dimensional swelling or an initial swelling followed by a gradual transition to H1. L~ with a high LPcontent gives a diffraction pattern showing only the first order diffraction maximum, possibly a result of undulations of the layers. The lamellar structure, however, was confirmed using freeze fracture electron microscopy (FFEM). Addition of LP to H1 gives an initial swelling followed by a transition to a transparent, highly viscous, isotropic phase, called the gel-phase (G). The diffraction pattern obtained from G yields little information on its structure. A large swelling of G with LP was observed. From the degree of swelling as a function of hydrocarbon content it was inferred that this phase consists of spherical aggregates forming a close-packed structure. Using FFEM, textures were visualized resembling those obtained from the isotropic mesophase (I1) in water-surfactant mixtures. Finally, geometrical factors are discussed that may play a role in the formation of the gel-phase.

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“…A sketch of the pseudo phase, diagram has been published previously [14] and is reproduced in Fig. 3c.…”

Section: X-ray Scatteringmentioning

confidence: 98%

Mesophases in mixtures of water and polyoxyethylene surfactant: Variations of repeat spacing with temperature and composition

Jousma

Joosten

Junginger

1988

Colloid & Polymer Sci

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Abstract." Lamellar (L~) and hexagonal (Hi) mesophases, formed in mixtures of water and polyethylene oxide (PEO) oleylethers (average EO-numbers 5 (a), 8.5 (b) and 14 (c)) and pure hexaoxyethylene dodecylether (d), were investigated with small-an~e X-ray diffraction. Analysis of repeat spacings shows a deviation from linear one-and two-dimensional swelling of L~ and P/l, respectively, when a transition to a mesophase with a larger curvature of the interface is approached. With regard to L~, in this respect similar behaviour is observed for a pure surfactant (d) and a surfactant with an EO-length distribution (b). It is proposed that, through the formation of aggregates of limited extent, water filled pores in the mesophases arise. This is confirmed by analysis of the intensity ratio of diffraction maxima of first and second order in L~. Models for finite aggregates are introduced. These consist of (1) lamellae, infinite in one direction and with variable length L in a direction perpendicular to the first, with cylindrical edges and (2) cylinders with variable length L bounded by spherical caps. According to these models, under certain conditions, finite aggregates may be formed without an increase of the interfadal area per surfactant molecule. Applying the models to the regions where non-linear swelling is observed, reasonable values for L are found, which decrease progressively when the phase transition is approached.

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Freeze-fracture electron microscopy study of mesophases in mixtures of polyoxyethylene (14) oleylether and water

Cited by 20 publications

References 29 publications

Rheological and phase behaviour of amphiphilic lipids

Rheological and phase behaviour of amphiphilic lipids

Changes of mesophase structure of BRIJ 96/water mixtures on addition of liquid paraffin

Mesophases in mixtures of water and polyoxyethylene surfactant: Variations of repeat spacing with temperature and composition

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