Amphiphilic Molecules and Liquid Crystals

Pershan, Peter S.

doi:10.1051/jphyscol:1979385

Cited by 16 publications

(4 citation statements)

References 8 publications

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“…Separate CP/MAS 13 C NMR experiments 6 have recently shown that the surfactant chain dynamics in silicate−surfactant and binary lyotropic liquid crystals are very similar, and that at room temperature, the silicate−surfactant mesophases are above their Krafft temperatures, consistent with their liquid crystalline properties. These results validate the use of the subscript α (e.g., H α and L α ), which designates the anisotropic liquid-like mobility of the alkyl CTA + chains in silicate−surfactant mesophases.…”

Section: Resultsmentioning

confidence: 96%

Alkaline Lyotropic Silicate−Surfactant Liquid Crystals

et al. 1997

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Multinuclear (2H, 13C, 29Si, 81Br) magnetic resonance spectroscopy, small-angle X-ray scattering, and polarized optical microscopy techniques have been used to investigate molecular and mesoscopic organization in silicate−surfactant lyotropic liquid crystals with hexagonal and lamellar morphologies under highly alkaline conditions. Such systems cooperatively self-assemble following the addition of a basic aqueous solution containing anionic silicate oligomers (e.g., double-four-ring species) to an isotropic micellar solution of cationic surfactant molecules (e.g., cetyltrimethylammonium bromide). Important similarities and differences are shown to exist between multicomponent silicate−surfactant and conventional binary lyotropic liquid crystals. Under highly alkaline conditions, the silicate−surfactant systems possess the characteristics of ordinary lyotropic liquid crystalline systems, though the balance of forces underlying their self-assembly is complicated by the richness of the aqueous silicate chemistry. This is the first comprehensive description of lyotropic silicate−surfactant liquid crystalline behavior, from which detailed insight is obtained into the molecular factors governing inorganic−organic mesophase formation in aqueous media.

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Section: Resultsmentioning

confidence: 96%

Alkaline Lyotropic Silicate−Surfactant Liquid Crystals

et al. 1997

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“…Diffusive transport of lipids and membrane proteins is of fundamental interest to physics, chemistry, and cell biology, because it typifies two-dimensional diffusion and plays a key role in intracellular signaling . For these reasons, a number of experiments have investigated diffusion in cell and model membrane systems. − However, existing ensemble methods that measure the average transport of many lipids (such as fluorescence recovery after photobleaching, FRAP, or electron spin resonance) implicitly rely on assumptions, such as the individual lipid motion is Brownian, , and thus cannot detect complex diffusive behaviors, including subdiffusion.…”

Section: Introductionmentioning

confidence: 99%

Single Lipid Diffusion in Langmuir Monolayers

2001

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Individual lipid movement in a monolayer is studied over long time intervals (500 s) by darkfield microscopy of single lipids labeled with gold colloids (30 or 100 nm in diameter). Dimyristoyl phosphatidylcholine in the fluid phase shows normal diffusion, with a diffusion coefficient of (1.1 ± 0.2) × 10-8 cm2/s. Since this is consistent with values derived from the diffusive transport of many lipids, the analysis of gold-tagged lipids in a monolayer provides a reliable picture of lipid diffusion on the level of single molecules.

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“…1 In a pioneering work, Albrecht, Gruler, and Sackmann 6 inferred the occurrence of such a mesophase ͑actually the smectic-C phase differing from the nematic by a finite out-of-plane tilt of molecular long axis͒ in Langmuir monolayers of phospholipids based on indirect evidence from thermodynamic and hydrodynamic behaviors. Although the possibility of 2D smectic-C and/or nematic phases was furthermore supported by numerous statistical theories [7][8][9][10][11][12][13][14][15][16][17][18][19] and computer simulations, [20][21][22][23][24][25] it had taken more than 20 years before this idea was proven to be real through the recent optical microscopic studies of Langmuir monolayers formed by certain thermotropic mesogenic molecules by Adams et al 26 and Tabe and Yokoyama.…”

Section: Introductionmentioning

confidence: 99%

Near-critical two-dimensional smectic-C to solid-like phase transition in azobenzene-derivative Langmuir monolayers

Tabe

Yokoyama

2001

The Journal of Chemical Physics

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Transition between two next-nearest-neighbor phases in a mixed Langmuir monolayer. A study by grazingincidence x-ray diffraction and Brewster-angle microscopyWe describe the results of a detailed study of two-dimensional ͑2D͒ smectic-C to solid-like phase transition in azobenzene-derivative Langmuir monolayers by the surface pressure vs area-per-molecule isotherm measurement, polarizing optical microscopy, and the grazing incidence synchrotron x-ray diffraction. The phase transition was observed to be weakly first order up to slightly above room temperature with a transition entropy less than 1.0 k B per molecule, accompanied by proper characteristics of a nearly ideal horizontal coexistence line on the isotherm, an abrupt change in optical texture, and the emergence of a conspicuous x-ray diffraction peak in the solid-like phase, which indicates a weak positional order with a correlation length of 10-20 nm. Analysis of the x-ray diffraction data within the framework of distorted hexagonal lattice suggests that the solid-like phase may be regarded as a 2D analog of smectic-L phase that is a hexatic smectic phase with the molecules tilted toward a direction between the nearest and the next-nearest bonds. At higher temperatures, the transition became less discontinuous and entirely disappeared above 40°C in all these experimental aspects. We argue that the transition is viewed as a 2D induced hexatic-hexatic transition ͑analog of smectic-C to smectic-L transition͒, which has an isolated critical point where the first-order transition comes to an end.

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Amphiphilic Molecules and Liquid Crystals

Cited by 16 publications

References 8 publications

Alkaline Lyotropic Silicate−Surfactant Liquid Crystals

Alkaline Lyotropic Silicate−Surfactant Liquid Crystals

Single Lipid Diffusion in Langmuir Monolayers

Near-critical two-dimensional smectic-C to solid-like phase transition in azobenzene-derivative Langmuir monolayers

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