Observation of the parabolic focal conic structure and a disclination/dislocation relationship in a dilute lyotropic phase

Benton, W. J.; Toor, E. W.; Miller, Clarence A.; Fort, Tomlinson

doi:10.1051/jphys:01979004001010700

Cited by 31 publications

(7 citation statements)

References 3 publications

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“…Previously, mesh intermediate phases of all types have been identified optically by their ‘fine mosaic' or parabolic focal conic (PFC) textures. , A similar texture has been reported in the C 30 EO 9 system . This PFC texture is indicative of a layered structure which has undergone a dilative stress, and has been associated with the lyotropic lamellar , and random mesh phases. ,, In the C 16 EO 6 /water system, on cooling fixed concentration samples between 51 and 59 wt % surfactant from the lamellar phase, PFC textures were seen at the transition to the L α H phase. The transition from the L α phase to the L α H phase is much easier to see in samples with large, homeotropic regions in which the PFC texture can form and be clearly seen.…”

Section: Resultsmentioning

confidence: 65%

Structure and Morphology of the Intermediate Phase Region in the Nonionic Surfactant C₁₆EO₆/Water System

1997

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The concentration interval of 48−62 wt % hexaethylene glycol n-hexadecyl ether (C16EO6) in deuterium oxide (2H2O) has been investigated using optical microscopy, 2H nuclear magnetic resonance, and small angle X-ray scattering and the detailed phase behavior established. On cooling from the lamellar phase (Lα), the phase sequence defected lamellar (Lα H), mesh intermediate (Int.), Ia3d cubic (V1), and hexagonal (H1) or hexagonal plus gel biphase (H1 + Lβ) was observed. On heating from the hexagonal or two-phase region, the region of intermediate and cubic phases formed on cooling is replaced by an Ia3d cubic phase. The mesh intermediate phase, formed on cooling, is demonstrated to have a rhombohedral structure, assigned the space group R3̄m. It represents a phase in which the water-filled defects of the higher temperature Lα H phase become correlated between layers. The formation of the phase is driven by the need to introduce more curvature into the interface as the temperature is decreased because of increased ethylene oxide head group (EO) hydration. The interlayer correlation arises from the strong, repulsive head group overlap interaction in this system.

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Section: Resultsmentioning

confidence: 65%

Structure and Morphology of the Intermediate Phase Region in the Nonionic Surfactant C₁₆EO₆/Water System

1997

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“…It is known that such textures grow from lamellar phases which are in a pseudoisotropic orientation if this orientation is a stress situation for the phase. The theoretical and experimental background of parabolic focal conics have been treated in detail. − It is the purpose of this paper to outline the experimental conditions for parabolic focal conic textures with nearly perfect lateral order. The parabolic focal conics presented in this paper only appear in two-phase lamellar−isotropic regions of various lyotropic systems.…”

Section: Introductionmentioning

confidence: 99%

“…The theoretical and experimental background of parabolic focal conics have been treated in detail. [10][11][12][13][14][15][16][17][18][19][20] It is the purpose of this paper to outline the experimental conditions for parabolic focal conic textures with nearly perfect lateral order. The parabolic focal conics presented in this paper only appear in two-phase lamellar-isotropic regions of various lyotropic systems.…”

Section: Introductionmentioning

confidence: 99%

Highly Ordered Parabolic Focal Conics in Lyotropic Systems

and

Thunig

1996

Langmuir

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Parabolic focal conics develop at 10−20 wt % surfactant in the two-phase lamellar−isotropic regions of various systems (SDS−hexanol−decane−water, alkylpolyglucoside APG600−fatty alcohols pentanol, hexanol, decanol, dodecanol, tetradecanol, oleyl alcohol). Extended regular quadratic two-dimensional lattices are formed in microslides (0.05−0.4 mm thickness) when only a small amount (10−15 wt %) of the isotropic phase is present. Five different focal planes can be visualized with the polarization microscope. The midplane focus gives pictures which look like primitive two-dimensional lattices of equally sized vesicle droplets. The 1:1 mixtures give irregular pattern formation. Removal of the isotropic phase by a 20 min centrifugation at 3000g leads to ordinary focal conics. Parabolic focal conics seem to be formed when the isotropic phase and the coexisting lamellar phase have comparable compositions, and this leads to the assumption that both phases should be in a near-critical state. The formation of parabolic focal conics looks more like a spinodal demixing than a crystallization process with nucleation. The very regular parabolic focal conics are transient states which change to mosaic textures, which look very similar to hexagonal fan textures, whereas polycrystalline parabolic focal conics transform to ordinary focal conics after several days or weeks.

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“…Rectangular optical capillaries (Vitro Dynamics, Inc., Rockaway, New Jersey) having an optical pathwidth of 100 ~m were used for the microscopy studies (16). Samples were imbibed by capillary action, either shortly after mixing or after storage at constant temperature for an extended period.…”

Section: Methodsmentioning

confidence: 99%

Phase behavior and network formation in a cationic surfactant‐fatty alcohol‐water system

Benton

Miller

Wells

1987

J Americ Oil Chem Soc

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Optical microscopy and differential scanning calorimetry were used to study the behavior of dilute aqueous systems containing mixtures of a long-chain cationic surfactant and long-chain fatty alcohols. Both alcoholrich particles with a lamellar structure and crystalline fibers containing considerable surfactant were observed, the fibers becoming more prevalent with decreasing values of the alcohol-to-surfactant ratio r. For values of r exceeding about two, separate fibrous and particulate regions were seen, the latter forming continuous networks throughout individual samples and hence contributing to the viscoelastic properties known to characterize these formulations. Studies of system behavior as a function of temperature showed that melting temperatures of the fibers and particles were about 55 C and 60 C, respectively. /

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Observation of the parabolic focal conic structure and a disclination/dislocation relationship in a dilute lyotropic phase

Cited by 31 publications

References 3 publications

Structure and Morphology of the Intermediate Phase Region in the Nonionic Surfactant C₁₆EO₆/Water System

Structure and Morphology of the Intermediate Phase Region in the Nonionic Surfactant C₁₆EO₆/Water System

Highly Ordered Parabolic Focal Conics in Lyotropic Systems

Phase behavior and network formation in a cationic surfactant‐fatty alcohol‐water system

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Observation of the parabolic focal conic structure and a disclination/dislocation relationship in a dilute lyotropic phase

Cited by 31 publications

References 3 publications

Structure and Morphology of the Intermediate Phase Region in the Nonionic Surfactant C16EO6/Water System

Structure and Morphology of the Intermediate Phase Region in the Nonionic Surfactant C16EO6/Water System

Highly Ordered Parabolic Focal Conics in Lyotropic Systems

Phase behavior and network formation in a cationic surfactant‐fatty alcohol‐water system

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Product

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Structure and Morphology of the Intermediate Phase Region in the Nonionic Surfactant C₁₆EO₆/Water System

Structure and Morphology of the Intermediate Phase Region in the Nonionic Surfactant C₁₆EO₆/Water System