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1

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Adhesion-induced lateral phase separation in membranes (2000)

Komura, S. ; Andelman, D.

Springer

The European physical journal 3 (2000), S. 259-271

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ISSN: 1292-895X

Keywords: PACS. 87.16.-b Subcellular structure and processes - 68.10.-m Fluid surfaces and fluid-fluid interfaces - 82.70.-y Disperse systems

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract: Adhesion between membranes is studied using a phenomenological model, where the inter-membrane distance is coupled to the concentration of sticker molecules on the membranes. The model applies to both adhesion of two flexible membranes and to adhesion of one flexible membrane onto a second membrane supported on a solid substrate. We mainly consider the case where the sticker molecules form bridges and adhere directly to both membranes. The calculated mean-field phase diagrams show an upward shift of the transition temperature indicating that the lateral phase separation in the membrane is enhanced due to the coupling effect. Hence the possibility of adhesion-induced lateral phase separation is predicted. For a particular choice of the parameters, the model exhibits a tricritical behavior. We also discuss the non-monotonous shape of the inter-membrane distance occurring when the lateral phase separation takes place. The inter-membrane distance relaxes to the bulk values with two symmetric overshoots. Adhesion mediated by other types of stickers is also considered.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s101890070018

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2

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Small-angle neutron scattering from Al-Zn and AI-Zn-Mg alloys during Guinier-Preston zone formation (1981)

Komura, S. ; Osamura, K. ; Fujii, H. ; [et al.]

Springer

Colloid & polymer science 259 (1981), S. 670-674

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ISSN: 1435-1536

Keywords: Neutron Scattering ; Small-angle Scattering ; Al-Zn Alloys ; Guinier-Preston zone ; Age-hardening

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Description / Table of Contents: Zusammenfassung Die Kleinwinkelstreuung der Neutronen von A1-6.8 at % Zn und Al-6.8 at % Zn- 0.1 at % Mg-Legierungen während der Guinier-Preston-Zonen-Bildung wurde am KUR (Kyoto Universität Reaktor) gemessen. Die Proben wurden aus 300 °C in Salzwasser von — 20 °C abgeschreckt und bei 77 K gehalten. Sie wurden bei 40 °C während der verschiedenen Zeitdauer von 0 bis 1000 Minuten mit der nachfolgenden Neutronenmessung bei 77 K gealtert. Die gemessene zeitliche Entwicklung des Streuquerschnittes kann qualitativ erklärt werden in übereinstimmung mit Saitos Formel, die aus zwei verschiedenen Teilen besteht, die der inkohärenten anomalen Schwankung und der kohärenten geordneten Struktur der Konzentration entsprechen.

Notes: Summary Small-angle neutron scattering from A1-6.8 at % Zn and Al-6.8 at % Zn-0.1 at % Mg alloys during Guinier-Preston zone formation have been measured at KUR (Kyoto University Reactor). The samples were quenched from 300 °C into brine at -20 °C and kept at 77 K. They were aged at 40 °C for various periods ranging from 0 up to 1000 minutes each with subsequent neutron measurement at 77 K. The observed temporal evolution of the cross section can be interpreted qualitatively in terms of Saito's formula which consists of two distinct parts due to the incoherent anomalous fluctuation and to the coherent ordered structure of the concentration.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01525036

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3

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Self-organization, phase transition and dynamics in amphiphilic systems (1997)

Komura, S. ; Seto, H. ; Takeda, T.

Springer

Colloid & polymer science 106 (1997), S. 1-5

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ISSN: 1435-1536

Keywords: Self-assembly ; phase transition ; slow dynamics ; amphiphiles ; neutron scattering

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract Recent studies on the structures, critical phenomena and slow dynamics in amphiphiles/ water/oil ternary systems using small-angle neutron scattering (SANS) and neutron spin echo (NSE) are reviewed. From the fitting of the scattering profiles of SANS to Teubner and Strey's and Gompper and Schick's formula we could obtain several structural and interaction parameters of a system. We observed critical scattering near the phase boundary into the decomposition of a system by SANS. The observed crossover from mean field to 3d-Ising behavior is interpreted in terms of an expression by Belyakov and Kiselev with an appropriate Ginzburg reduced temperature. We observed NSE signal from a system and obtained effective diffusion coefficients for the shape fluctuations of the interfacial films in lamellar phase which has two decaying processes. The powerfulness of neutron-scattering methods to characterize the structure and dynamics of amphiphilic systems is illustrated.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01189483

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4

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Microemulsions under steady shear flow (1997)

Komura, S. ; Kodama, H.

Springer

Colloid & polymer science 106 (1997), S. 75-78

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ISSN: 1435-1536

Keywords: Microemulsions ; rheology ; shear flow ; Ginzburg ; Landau model

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract Dynamic response of microemulsions to shear deformation on the basis of two-order-parameter time dependent Ginzburg Landau model is investigated by means of cell dynamical system approach. Time evolution of anisotropic factor and excess shear stress under steady shear flow is studied by changing shear rate and total amount of surfactant. As the surfactant concentration is increased, overshoot peak height of the anisotropic factor increases whereas that of the excess shear stress is almost unchanged.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01189495

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5

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Pressure-induced phase transition from disordered microemulsion to lamellar structure in a water/AOT/n-decane system (1997)

Nagao, M. ; Seto, H. ; Komura, S. ; [et al.]

Springer

Colloid & polymer science 106 (1997), S. 86-90

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ISSN: 1435-1536

Keywords: Neutron scattering ; microemulsion ; lamellar structure ; first-order phase transition ; high pressure

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract Pressure effect on the structure of a 3-component micro-emulsion AOT/water/n-decane was investigated by means of small-angle neutron scattering. The measured pressure range was from 0.1 (1 atm) to 83.5 MPa. The present sample was at the composition of the molar ratio of [water]/[AOT]=40.8 and the volume fraction of both water and AOT against the whole volume 0.6. A phase transition from disordered microemulsion to ordered lamellar structure was observed at about 50 MPa through a coexisting region. The pressure dependence of the repeat distance and the correlation length in both high- and low-pressure phases was calculated from the scattering profiles by fitting to Teubner and Strey's formula and/or a single Gaussian. The low-pressure phase became more disordered with increasing pressure and then the phase transition to the ordered phase occurred.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01189498

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6

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Structural changes and interaction parameters in amphiphilic system C12E5/water/n-octane (1997)

Ghosh, S. K. ; Matsuba, J. ; Komura, S. ; [et al.]

Springer

Colloid & polymer science 106 (1997), S. 91-97

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ISSN: 1435-1536

Keywords: Interaction parameter ; lamella ; microemulsion ; structure ; parameter ; spin-lattice model

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract A ternary amphiphilic system consisting of water,n-octane and nonionic amphiphile C12E5 has been studied by means of small-angle X-ray scattering in order to understand the differences of structures and interaction parameters among the low-temperature microemulsion (LTM), middle-temperature lamellar (MTL) and high-temperature microemulsion (HTM) phases. Scattering spectra for microemulsion phases are analyzed by the phenomenological scattering formula of Teubner and Strey (TS), whereas the Ornstein-Zernike scattering formula was combined with the TS formula for the lamellar phase. From the fitting parameters we have determined structural parameters such as the repeat distanceD, correlation lengthξ and 2πξ/D for both the lamellar and the two microemulsion phases. Observed results suggest that the LTM phase is more ordered than the HTM phase. Thermal fluctuations in the HTM phase may make the structure less ordered than that in the LTM phase. Again a finite value ofkξ suggests the existence of an imperfectly ordered MTL phase. Microscopic interaction parameters were determined in terms of Gompper and Schick's (GS) microscopic spin-lattice theory for a suitable lattice parameterd=15 Å. Observed interaction parameters have reasonable agreement with GS's prediction. The inequality condition ¦L¦〉J/4, suggests strong amphiphilic interaction for all three phases.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01189499

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7

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Structure functions and interfacial mean curvatures in a ternary amphiphilic system C12E5/water/n-octane (1997)

Ghosh, S. K. ; Komura, S. ; Seto, H. ; [et al.]

Springer

Colloid & polymer science 106 (1997), S. 98-103

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ISSN: 1435-1536

Keywords: Amphiphile ; microemulsion ; lamella ; partial structure function ; mean curvature

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract Partial structure functions and mean curvatures of a ternary amphiphilic system consisting of water,n-octane and nonionic amphiphile C12E5 with equal volume fraction of oil and water have been studied by means of small-angle neutron scattering (SANS). Isotopic contrast variation technique was used to obtain suitable scattering contrasts of oil and water. We observed that the cross partial structure functions, that arise from the correlation between water-surfactant or oil-surfactant, change sign when the temperature passes through the hydrophile-lipophile balance (HLB) point. It indicates that the interaction parameterC of the spin-lattice model invert on HLB line. We have calculated mean curvatures considering that water or oil molecules can partially penetrate into the surfactant film. Experimental results show that mean curvatures increase as the temperature increases at a rate of 1.5×10−3 (Å−1 K−1).

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01189500

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Small angle neutron scattering studies of critical phenomena in a three-component microemulsion (1997)

Seto, H. ; Komura, S. ; Wignall, G. D. ; [et al.]

Springer

Colloid & polymer science 106 (1997), S. 104-107

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ISSN: 1435-1536

Keywords: Small-angle neutron ; scattering ; critical phenomena ; crossover ; microemulsion

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract Critical density fluctuations of a “water-in-oil” microemulsion consisting of water, benzene, and BHDC (benzyldimethyl-n-hexadecyl ammonium chloride) have been observed near the phase boundary by a small-angle neutron scattering (SANS). The observed profiles were well described by the product of a form factor of spherical droplets and a structure factor, consisting of a term describing the inter-droplet correlations and also an Ornstein-Zernike component describing the droplet density fluctuations. Allowance was also made for the droplet polydispersity, though the width of the distribution turned out to be very small (1–2%). The observed temperature dependence of the osmotic compressibility was fitted using the crossover function proposed by Belyakov et al., and the Ginzburg numbers were obtained of the order 10−2. These results indicate that longrange inter-droplet forces are not significant in this system, which displays upper critical solution temperature (UCST) behavior. In contrast, previous studies of systems displaying with lower critical solution temperature (LCST) behavior [e.g. water,n-decane and AOT (dioctyl sulfosuccinate sodium salt)] indicate that long-range interactions appear to dominate the phase separation behavior.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01189501

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