Phase Separation (phase + separation)

Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Kinds of Phase Separation

  • induced phase separation
  • liquid phase separation
  • reaction-induced phase separation
  • vertical phase separation

  • Terms modified by Phase Separation

  • phase separation behavior
  • phase separation process

  • Selected Abstracts


    The Joint Research Program "CPR Precipitation" , Breakthroughs in the Understanding of Kinetic Pathways for the Early Stages of Phase Separation,

    ADVANCED ENGINEERING MATERIALS, Issue 12 2006
    G. Martin
    The CNRS joint research program, "CPR Precipitation", has been carefully prepared by the industrial initiators. Very significant results were obtained: they are summarized in the following and presented in this meeting. As for the future, the CPR has catalyzed the formation of a community of promising scientific interest: it would be of common benefit to stabilize this community by an appropriate further support. [source]


    Flexible Organic Solar Cells: Nanoscale Phase Separation and High Photovoltaic Efficiency in Solution-Processed, Small-Molecule Bulk Heterojunction Solar Cells (Adv. Funct.

    ADVANCED FUNCTIONAL MATERIALS, Issue 19 2009
    Mater.
    The inside cover of this issue illustrates the fabrication of lightweight and flexible organic solar cells, developed by B. Walker et al. on page 3063, from a solution of fullerene and diketopyrrolopyrrole-based materials. The texture of the organic film on the substrate was taken from an atomic force microscope phase image of the high performance device (4.4% power conversion efficiency), showing the phase separation behavior of the two molecular semiconducting materials. [source]


    Nanoscale Phase Separation and High Photovoltaic Efficiency in Solution-Processed, Small-Molecule Bulk Heterojunction Solar Cells

    ADVANCED FUNCTIONAL MATERIALS, Issue 19 2009
    Bright Walker
    Abstract Research relating to organic solar cells based on solution-processed, bulk heterojunction (BHJ) films has been dominated by polymeric donor materials, as they typically have better film-forming characteristics and film morphology than their small-molecule counterparts. Despite these morphological advantages, semiconducting polymers suffer from synthetic reproducibility and difficult purification procedures, which hinder their commercial viability. Here, a non-polymeric, diketopyrrolopyrrole-based donor material that can be solution processed with a fullerene acceptor to produce good quality films is reported. Thermal annealing leads to suitable phase separation and material distribution so that highly effective BHJ morphologies are obtained. The frontier orbitals of the material are well aligned with those of the fullerene acceptor, allowing efficient electron transfer and suitable open-circuit voltages, leading to power conversion efficiencies of 4.4,,0.4% under AM1.5G illumination (100,mW cm,2). Small molecules can therefore be solution processed to form high-quality BHJ films, which may be used for low-cost, flexible organic solar cells. [source]


    Vertical Phase Separation in Poly(3-hexylthiophene): Fullerene Derivative Blends and its Advantage for Inverted Structure Solar Cells

    ADVANCED FUNCTIONAL MATERIALS, Issue 8 2009
    Zheng Xu
    Abstract A method which enables the investigation of the buried interfaces without altering the properties of the polymer films is used to study vertical phase separation of spin-coated poly(3-hexylthiophene) (P3HT):fullerene derivative blends. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) analysis reveals the P3HT enrichment at the free (air) surfaces and abundance of fullerene derivatives at the organic/substrate interfaces. The vertical phase separation is attributed to the surface energy difference of the components and their interactions with the substrates. This inhomogeneous distribution of the donor and acceptor components significantly affects photovoltaic device performance and makes the inverted device structure a promising choice. [source]


    Effects of Solvent Mixtures on the Nanoscale Phase Separation in Polymer Solar Cells,

    ADVANCED FUNCTIONAL MATERIALS, Issue 12 2008
    Yan Yao
    Abstract The mixed solvent approach has been demonstrated as a promising method to modify nanomorphology in polymer solar cells. This work aims to understand the unique role of the additive in the mixture solvent and how the optimized nanoscale phase separation develops laterally and vertically during the non-equilibrium spin-coating process. We found the donor/acceptor components in the active layer can phase separate into an optimum morphology with the additive. Supported by AFM, TEM and XPS results, we proposed a model and identified relevant parameters for the additive such as solubility and vapor pressures. Other additives are discovered to show the ability to improve polymer solar cell performance as well. [source]


    Amphiphilic Homochiral Oligopeptides Generated via Phase Separation of Nonracemic , -Amino Acid Derivatives and Lattice-Controlled Polycondensation in a Phospholipid Environment

    HELVETICA CHIMICA ACTA, Issue 11 2003
    Irina Rubinstein
    Racemic S -ethyl thioesters of N, -stearoyllysine (=,S -ethyl (R,S)-2-amino-6-(stearoylamino)hexanethioate) and S -ethyl thioesters of , -stearyl glutamic acid (=stearyl (R,S)-4-amino-5-(ethylsulfanyl)-5-oxopentanoate) self-assemble as separated two-dimensional crystalline monolayers within an achiral phospholipid environment of racemic 1,2-dipalmitoylglycerol (DPG) and 1,2-dipalmitoylglycero-3-phosphoethanolamine (DPPE), as demonstrated by grazing-incidence X-ray-diffraction (GIXD) measurements performed on the surface of H2O. Lattice-controlled polycondensation within these crystallites with deuterium-enantiolabeled monomers was initiated by injecting aqueous solutions of Ag+ or I2/KI beneath the monolayers, which yielded mixtures of diastereoisomeric oligopeptides containing up to six to eight repeating units, as analyzed by MALDI-TOF mass spectrometry. Analysis of the diastereoisomeric distribution showed an enhanced relative abundance of the oligopeptides with homochiral sequences containing three or more repeating units. Within the DPPE monolayers, the nucleophilic amino group of the phospholipid operates as an initiator of polymerization at the periphery of the monomer two-dimensional crystallites. Enhanced relative abundance of enantiomerically enriched homochiral oligopeptides was obtained by the polycondensation of nonracemic monomers. This enhancement indicated a phase separation into racemic and enantiomorphous monomer crystallites within the phospholipid environment, although this separation could not be observed directly by GIXD. A possible role that might have been played by crystalline assemblies for the abiotic generation and amplification of oligopeptides with homochiral sequences is discussed. [source]


    Organic Electronics: Improved Performance of Polymer Bulk Heterojunction Solar Cells Through the Reduction of Phase Separation via Solvent Additives (Adv. Mater.

    ADVANCED MATERIALS, Issue 8 2010
    8/2010)
    The fabrication of bulk heterojunction organic solar cells from solution-casting techniques using low-cost materials makes them a promising new technology for converting sunlight into electricity. T.-Q. Nguyen, G. C. Bazan, et al. report on p. E63 that undesirable large-scale aggregation and phase separation that may arise during deposition can be reduced by incorporating a small amount of a well-chosen solvent additive. [source]


    Altering the Thermodynamics of Phase Separation in Inverted Bulk-Heterojunction Organic Solar Cells

    ADVANCED MATERIALS, Issue 30 2009
    Chang Su Kim
    Organic solar cells: By incorporating nonvolatile additives into blends of P3HT:PCBM, the efficiencies of inverted bulk-heterojunction solar cells are improved almost twofold (see figure). These additives selectively partition into the P3HT phase, effectively increasing phase separation between the P3HT and PCBM. [source]


    Janus Supraparticles by Induced Phase Separation of Nanoparticles in Droplets

    ADVANCED MATERIALS, Issue 19 2009
    Rhutesh K. Shah
    Biphasic Janus particles with a precisely tunable internal morphology are fabricated using a novel, versatile, and robust technique. This technique can be used in conjunction with microfluidics to produce monodisperse particles, or can be combined with bulk emulsification techniques to produce large quantities of particles. [source]


    Formation of Network and Cellular Structures by Viscoelastic Phase Separation

    ADVANCED MATERIALS, Issue 18 2009
    Hajime Tanaka
    Abstract Network (sponge) and cellular structures are often seen in various types of materials. Materials with such structures are generally characterized by light weight and high mechanical strength. The usefulness of such materials is highlighted, for example, by the remarkable material properties of bone tissue, which often has a highly porous structure. In artificial materials, plastic and metallic foams and breads have such structures. Here, we describe a physical principle for producing network and cellular structures using phase separation, and its potential applications to the morphological control of materials spanning from soft to hard matter. [source]


    Phase Separation of Polyfluorene-Based Blend Films and Its Influence on Device Operations,

    ADVANCED MATERIALS, Issue 11 2006
    Y. Xia
    Vertical phase separations have been found in blend films (TFB:F8BT) of polymer light-emitting diodes, giving rise to better device performances. A TFB wetting layer is present over most of the bottom interface with the substrate, as evidenced by the fluorescent microscopy images after top layers are etched away by oxygen plasma (see figure). [source]


    Characterization of Phase Separation and Thermal History Effects in Magnesium Silicate Glass Fibers by Nuclear Magnetic Resonance Spectroscopy

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2009
    Jonathan F. Stebbins
    Liquid,liquid immiscibility, leading to the separation of silica-rich and silica-poor domains, is a common phenomenon in binary silicate glasses, but can be difficult to detect and characterize when rapid cooling results in nano-scale domain dimensions. 29Si nuclear magnetic resonance (NMR) spectroscopy can be very useful for detecting such phase separation, because the exclusion of paramagnetic impurity ions from the silica-rich regions can greatly slow their spin-lattice relaxation rates. Properly designed experiments can therefore largely isolate the NMR signals from high-silica and low-silica domains, and thus provide information about their proportions, compositions, and short- to intermediate-range structures. We demonstrate this approach here for fiber glasses that are predominantly magnesium, or calcium-magnesium silicates, with minor contents of alumina. For bulk compositions within the known region of stable liquid immiscibility, phase separation occurs even when extremely rapid cooling yields fibers less than 1 ,m in mean diameter. Slower cooling increases the extent of separation, while the addition of small amounts of alumina reduces it. [source]


    Indication of Local Phase Separation in Polyimide/Silica Hybrid Polymers,

    MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2010
    Antonino Bartolotta
    Abstract PI/SiO2 hybrid polymers involving the in situ generation of SiO2 particles through the sol/gel route have emerged as promising materials in many fields of modern technology thanks to their unique structural characteristics. In this paper their structural and dynamic properties were investigated by FT-IR and DMTA as a function of SiO2 content. All data consistently highlight a loosening of polymeric structure due to the presence of SiO2 nanoparticles and suggest a silica-induced structural change most probably due to a sub-micrometer scale SiO2 phase separation. Our results demonstrate how the analysis of sub-glass ,-relaxation dynamics can be exploited to investigate sub-micro phase segregation in such materials. [source]


    Phase Separation and Organisation of Colloidal Spheres Suspended in Sheared Lyotropic Liquid-Crystalline Polymers

    MACROMOLECULAR RAPID COMMUNICATIONS, Issue 11 2005
    Shanju Zhang
    Abstract Summary: Organisation behaviours of spherical particles suspended in sheared, lyotropic, liquid-crystalline polymer solutions have been investigated using polarizing optical microscopy. We find that in a nematic phase the particles phase separate and adopt anisotropic chain-like structures along the director. An earring defect is observed around a single particle whereas a cross or strings defect between neighbouring particles is found to serve as a repulsive barrier to prevent the particles from contacting each other. A theoretical analysis is presented to explain this new phenomenon. An optical micrograph of 0.01 wt.-% glass spheres suspended in a nematic solution of 40 wt.-% ethyl cellulose in chloroform under an external shear force. [source]


    Reactive processing of syndiotactic polystyrene with an epoxy/amine solvent system

    MACROMOLECULAR SYMPOSIA, Issue 1 2003
    Jaap Schut
    Abstract Syndiotactic polystyrene (sPS) is a new semi-crystalline thermoplastic which is believed to fill the price-performance gap between engineering and commodity plastics. In order to reduce the high processing temperature of sPS (>290C), an epoxy-amine model system was used as a reactive solvent. Such a processing aid can be used to achieve a 50 to 500 fold lowering of the melt viscosity. When initially homogeneous solutions of sPS in a stoechiometric epoxy-amine mixture are thermally cured, Reaction Induced Phase Separation (RIPS) takes place, leading to phase separated thermoplastic-thermoset polymer blends. We focus our study on low (wt% sPS < 20%) and high concentration blends (wt% sPS > 60%) prepared by two processing techniques (mechanical stirring in a laboratory reactor or internal mixer/ reactive extrusion respectively). These blends have different potential interests. Low concentration blends (sPS domains in an epoxy-amine matrix) are prepared to create new, tunable blend morphologies by choosing the nature of the phase separation process, i.e. either crystallisation followed by polymerization or polymerization followed crystallisation. High concentration blends (sPS matrix containing dispersed epoxy-amine particles after RIPS) are prepared to facilitate the extrusion of sPS. In this case, the epoxy amine model system served as a reactive solvent. The time to the onset of RIPS is in the order of 7-9 min for low concentration blends, while it increases to 20-45 min for high concentration samples, as the reaction rates are substantially slowed down due to lower epoxy and amine concentrations. During the curing reaction the melting temperature of sPS in the reactive solvent mixture evolves back from a depressed value to the level of pure sPS. This indicates a change in the composition of the sPS phase, caused by (complete) phase separation upon reaction. We conclude that our epoxy amine system is suited for reactive processing of sPS, where final properties depend strongly on composition and processing conditions. [source]


    Effect of Concentration Gradient on the Morphology Development in Polymer Solutions Undergoing Thermally Induced Phase Separation

    MACROMOLECULAR THEORY AND SIMULATIONS, Issue 7 2007
    Bai Tao Jiang
    Abstract Anisotropic porous polymeric materials fabricated from the phase separation method via spinodal decomposition are used in various practical engineering applications. We studied the formation of anisotropic porous polymeric materials numerically, by imposing an initial linear concentration gradient across a model polymer solution. The initial concentration gradient is placed at three different regions of the polymer sample for comparison purposes. All the simulation results are in good agreement with published experimental observations, which are reported from the applications of porous polymeric membranes. The structure development shows that an anisotropic porous morphology forms when an initial linear concentration gradient is applied to the model polymer solution. [source]


    A Discrete, Space Variation Model for Studying the Kinetics of Shape Deformation of Vesicles Coupled with Phase Separation

    MACROMOLECULAR THEORY AND SIMULATIONS, Issue 5 2006
    Jianfeng Li
    Abstract Summary: The evolution dynamics of phase separation, coupled with shape deformation of vesicles is described by using dissipative dynamic equations, specifically the time-dependent Ginzburg-Landau (TDGL) equations. In order to improve the numerical stability and thus to efficiently deal with a large deformation of vesicles, a new algorithm, namely the discrete space variation model (DSVM) has been developed for the first time. The algorithm is based on the variation of the discretized free-energy functional, which is constructed in discrete membrane space, in contrast to the commonly used continuous free-energy functional. For the sake of numerical tractability, only the cylindrical vesicles (2D), with two components, are taken into consideration to illustrate the efficiency and validity of new algorithm. The simulation results, based on the DSVM algorithm have been compared with those from both linear analysis and strong segregation theory using the continuous space free-energy functional. It is found that the DSVM algorithm can correctly describe the coupling between the lateral phase-separation on the vesicle membrane and the vesicle shape deformation, both for early and late stages. A flower-like vesicle obtained by DSVM simulation. [source]


    Phase separation of liquid-liquid two-phase flow at a T-junction

    AICHE JOURNAL, Issue 1 2006
    L. Yang
    Abstract The phase separation of liquid-liquid two-phase flow at a T-junction has been studied using kerosene and deionized water as working fluids and a T-junction with a horizontal main pipe and a vertically upward side arm. Separation data are evaluated by a new criterion: separation efficiency. The results show that the T-junction is highly efficient at separating two immiscible liquids when the flows approaching the T-junction are stratified and when the fractional mass take offs close to the inlet kerosene mass fraction. A new model has been proposed for the phase separation. Comparison between the model and the experimental data shows that the data is well represented by the model. 2005 American Institute of Chemical Engineers AIChE J, 2006 [source]


    Phase separation of polymer-functionalized SWNTs within a PMMA/polystyrene blend

    JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2009
    James D. Mayo
    Abstract Phase separation of polystyrene (PS) and poly(methyl methacrylate) (PMMA) blends was used as a means to segregate PS- or PMMA-functionalized single-walled carbon nanotubes (SWNTs) in thin films. Dilute solutions (5 wt % in THF) of 1:1 PS/PMMA blends containing the functionalized nanotubes were spin cast and annealed at 180 C for 12 h. Two different polymer molecular weights were used (Mn = 8000 or Mn = 22,000), and were of approximately equivalent molecular weight to those attached to the surface of the nanotubes. Nanotube functionalization was accomplished using the Cu(I)-catalyzed [3 + 2] Huisgen cycloaddition, in which alkyne-decorated nanotubes were coupled with azide-terminated polymers, resulting in polymer-SWNT conjugates that were soluble in THF. Characterization of the annealed films by scanning Raman spectroscopy, which utilized the unique Raman fingerprint of carbon nanotubes, enabled accurate mapping of the functionalized SWNTs within the films relative to the two phase-separated polymers. It was found that nanotube localization within the phase-separated polymer films was influenced by the type of polymer attached to the nanotube surface, as well as its molecular weight. 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 450,458, 2009 [source]


    Highly fluorinated compounds induce phase separation in, and nanostructuration of liquid media.

    JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 14 2006
    Possible impact on, use in chemical reactivity control
    Abstract Liquid perfluorocarbons-like supercritical CO2 -provide valuable reaction media that can facilitate the separation of reaction products and the recovery of catalysts. Chemistry in fluorous media requires that some of the protagonist molecules, and in particular the catalysts, be grafted with one or more perfluoroalkylated chains. These chains, due to powerful hydrophobic and lipophobic effects, tend to self-assemble and induce the formation of a variety of nanocompartmented supramolecular architectures and colloids, such as micelles, vesicles, tubules, monolayers, and emulsions, thus generating microheterogenicity in the reaction medium. Fluorinated amphiphiles are, for example, known to generate fibrous gels in fluorous, organic, and aqueous media. Phase separation, nanocompartmentation, and interface-driven parameters can thus complicate otherwise simple chemistry. Conversely, they can provide useful micro- and nanoreactors and templates. 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4251,4258, 2006 [source]


    Liquid Chromatography of Synthetic Polymers under Limiting Conditions of Insolubility III

    MACROMOLECULAR SYMPOSIA, Issue 1 2007
    Application of Monolithic Columns
    Abstract Summary Performance was evaluated of silica based commercial monolithic rod-like columns in liquid chromatography of synthetic polymers under limiting conditions of enthalpic interactions (LC LC). LC LC employs the barrier effect of the pore permeating and therefore slowly eluting small molecules toward the pore excluded, fast eluting macromolecules. Phase separation (precipitation) barrier action was applied in present study. The barrier was created either by the narrow pulse of an appropriate nonsolvent injected into the column just before the sample solution (LC LC of insolubility , LC LCI) or by the eluent itself. In the latter case, the polymer sample was dissolved and injected in a good solvent (LC LC of solubility , LC LCS). In LC LCI, polymer species cannot break thru the nonsolvent zone while in LC LCS they cannot enter eluent, which is their precipitant. Therefore, polymer species keep moving in the zone of their original solvent. Macromolecules eluting under the LC LC mechanism leave the column in the retention volume (VR) roughly corresponding to VR of the low molar mass substances and can be efficiently separated from the polymer species non-hindered by the barrier action. The known advantages of monoliths were confirmed. From the point of view of LC LCI and LC LCS the most important quality of monolithic columns represents their excellent permeability, which allows both working at high flow rates and injecting very high (in the range of 5%) sample concentrations. Monolithic column tolerate also extremely high molar mass samples (M>10,000 kg,,mol,1). On the other hand, the mesopores (separation pores) of the tested monoliths exhibited rather small volume and wide size distribution. These shortcomings partially impair the permeability advantage of monoliths because in order to obtain high LC LC separation selectivity a tandem of several monolithic columns must be applied. Presence of large mesopores also reduces applicability of monolithic columns for molar masses below about 50 kg,,mol,1 because VRs of polymers eluted behind the barrier are similar to that of freely eluting species. The non- negligible break-thru phenomenon was observed for the very high polymer molar masses largely eluting behind the barrier. It is assumed that the fraction of very large mesopores present in the monoliths or association/microphase separation of macromolecules may be responsible for this phenomenon. This is why the presently marketed SiO2 monolithic columns are mainly suitable for the fast purification of the LC LC eluting macromolecules from the polymeric admixtures non-hindered by the barrier-forming liquid. Still, monolithic columns have large potential in the LC LCI and LC LCS procedures provided size (effective diameter) of the mesopores can be reduced and their volume increased. [source]


    In situ monitoring of reaction-induced phase separation with modulated temperature DSC

    MACROMOLECULAR SYMPOSIA, Issue 1 2003
    Steven Swier
    Abstract A linearly polymerizing and network forming epoxy-amine system, DGEBA-aniline and DGEBA-MDA, respectively, will be modified with 20 wt% and 50 wt% of a high- Tg thermoplastic poly(ether sulphone) (Tg=223C), respectively, both showing LCST-type demixing behavior. Reaction-induced phase separation (RIPS) in these modified systems is studied using Modulated Temperature DSC (MTDSC) as an in situ tool. Phase separation in the linear system can be probed by vitrification of the PES-rich phase, occurring at a higher conversion than the actual cloud point from light scattering measurements. The negative slope of the cloud point curve in a temperature-conversion-transformation diagram unambiguously shows the LCST-type demixing behavior of this system, while the relation between the composition/glass transition of the PES-rich phase and the cure temperature is responsible for the positive slope of its vitrification line. Phase separation in the network forming system appears as reactivity increases at the cloud point due to the concentration of reactive groups. Different mixture compositions alter the ratio between the rate of phase separation and the rate of reaction, greatly affecting the morphology. Information about this in situ developed structure can be obtained from the heat capacity evolutions in non-isothermal post-cures. [source]


    Phase separation in SiOx films annealed under enhanced hydrostatic pressure

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 12 2008
    G. Yu.
    Abstract The effect of enhanced hydrostatic pressure (HP, (10,12) 108 Pa) on thermally stimulated phase decomposition of silicon suboxide layers processed at 450,1000 C was investigated by infrared spectroscopy and photoluminescence measurements. HP stimulates decomposition of non-stoichiometric SiOx most efficiently at about 450 C. In spite of enhanced SiOx decomposition, visible photoluminescence appears in HP-treated samples at higher annealing temperatures in comparison to those annealed under ambient pressure (AP, 105 Pa). Contrary to that, application of HP results in essential enhancement of near-infrared emission at lower annealing temperatures as compared to processing under AP. This can be related to pressure-stimulated crystallization of Si inclusions. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Morphology profiles generated by temperature gradient in PMMA modified epoxy system

    POLYMER ENGINEERING & SCIENCE, Issue 11 2001
    P. M. Stefani
    A diglycidyl ether of bisphenol-A (DGEBA) epoxy resin was modified with 15 wt% of poly(methylmethacrylate) (PMMA) and cured with a stoichiometric amount of 4,4,-diamino diphenyl methane (DDM). The reactive mixture was cured in a heated mold with different gradients of temperature. Temperature profiles in the mold were imposed by generation of a heat flux from the base, supported on a hot plate, and the top, cooled with water; they were measured along the mold. Depending on the thermal history in each position of the mold, the competition between the phase-separation process and reaction kinetics produces opaque or transparent zones. Phase separation can also occur in the postcure process while the gelation does not take place before. Therefore, a thermoset plate with gradient of morphology and properties was obtained. Mass fractions of PMMA dissolved in the matrix were calculated with the Fox equation from glass transition temperatures measured along the mold. They were related to morphologies developed during curing. The superposition of the phase diagrams with the conversion-temperature trajectories during cure permitted an explanation of the morphology gradients generated. [source]


    Photoreactions and lateral patterning in Langmuir and Langmuir,Blodgett films

    THE CHEMICAL RECORD, Issue 2 2007
    Mutsuyoshi Matsumoto
    Abstract Reversible morphological changes occur with photoisomerization of azobenzene in Langmuir,Blodgett (LB) films complexed with polycations, which contradicts an implicit assumption of the concept of free volume that two-dimensional film structures are preserved during the photoisomerization. J-aggregates of chromophores are formed by two processes. The first process is "light-induced J-aggregation" in which photoisomerized molecules form J-aggregates. The other process is "triggered J-aggregation," in which photoisomerization of one of the components triggers J-aggregation of another chemical species in the mixed films. Both processes of J-aggregation are in many cases accompanied by large morphological changes of the films. However, LB films fabricated using processes under isobaric conditions do not change their morphology during light-induced J-aggregation and are patterned with J-aggregates using ultraviolet illumination through a photomask. Phase separation in mixed LB films gives rise to two-dimensional patterns, which are used to fabricate templates by using an amphiphilic silane-coupling agent as one of the components in the mixed LB films. Nanopatterns are also fabricated. 2007 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 7: 69,77; 2007: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20099 [source]


    Liquid-liquid phase separation in acetone solutions of palm olein: Implications for solvent fractionation

    EUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 4 2007
    Kevin W. Smith
    Abstract The quality of palm mid fractions (PMF) obtained by dry fractionation has increased, but the best-quality PMF for application in many confectionery fats are still produced by solvent fractionation. In the present study, liquid-liquid phase separation has been observed in acetone solutions both for pure triacylglycerols and for palm olein. The temperature at which phase separation occurs increases as the oil concentration is increased and linearly as the water content of the system is increased. The triacylglycerol compositions of the two liquid phases that form do not differ. However, the oil-rich phase is depleted with respect to the polar components. The temperature at which liquid-liquid phase separation occurs is reduced by about 0.2 and 0.4,C per percent of free fatty acids and diacylglycerols, respectively. When oil-rich droplets appear, crystallisation occurs within them rather than in the oil-depleted phase, due to the higher oil concentration. Thus, liquid-liquid phase separation prior to crystallisation raises the nucleation temperature but may lead to a greater concentration of entrained olein in the filter cake, leading to a poorer-quality PMF. [source]


    Atom Probe Tomography II.

    ADVANCED ENGINEERING MATERIALS, Issue 12 2006
    The Precipitation in Al Base Alloys
    Abstract This paper presents two illustrations of the study of phase separation in Al-based alloys by means of tomographic atom probe. In an AlMgSi alloy, calculations of pair correlation functions have revealed that the nature of solute short range order differs from a pre-aged specimen to a non-pre-aged specimen. This results in different responses to aged hardening treatments. Concerning Al3(Zr,Sc)-type dispersoids observed in another Al-based alloy, they are found to display a core-shell structure wherein Zr is mainly present in the dispersoids periphery. This duplex structure is likely to explain the relative stability of Al3(Zr,Sc) dispersoids. [source]


    Presence of membrane ecdysone receptor in the anterior silk gland of the silkworm Bombyx mori

    FEBS JOURNAL, Issue 15 2004
    Mohamed Elmogy
    Nongenomic action of an insect steroid hormone, 20-hydroxyecdysone (20E), has been implicated in several 20E-dependent events including the programmed cell death of Bombyx anterior silk glands (ASGs), but no information is available for the mode of the action. We provide evidence for a putative membrane receptor located in the plasma membrane of the ASGs. Membrane fractions prepared from the ASGs exhibit high binding activity to [3H]ponasterone A (PonA). The membrane fractions did not contain conventional ecdysone receptor as revealed by Western blot analysis using antibody raised against Bombyx ecdysone receptor A (EcR-A). The binding activity was not solubilized with 1,m NaCl or 0.05% (w/v) MEGA-8, indicating that the binding sites were localized in the membrane. Differential solubilization and temperature-induced phase separation in Triton X-114 showed that the binding sites might be integrated membrane proteins. These results indicated that the binding sites are located in plasma membrane proteins, which we putatively referred to as membrane ecdysone receptor (mEcR). The mEcR exhibited saturable binding for [3H]PonA (Kd = 17.3 nm, Bmax = 0.82 pmolmg,1 protein). Association and dissociation kinetics revealed that [3H]PonA associated with and dissociated from mEcR within minutes. The combined results support the existence of a plasmalemmal ecdysteroid receptor, which may act in concert with the conventional EcR in various 20E-dependent developmental events. [source]


    The assembly factor P17 from bacteriophage PRD1 interacts with positively charged lipid membranes

    FEBS JOURNAL, Issue 20 2000
    Juha M. Holopainen
    The interactions of the assembly factor P17 of bacteriophage PRD1 with liposomes were investigated by static light scattering, fluorescence spectroscopy, and differential scanning calorimetry. Our data show that P17 binds to positively charged large unilamellar vesicles composed of the zwitterionic 1-palmitoyl-2-oleoyl-phosphatidylcholine and sphingosine, whereas only a weak interaction is evident for 1-palmitoyl-2-oleoyl-phosphatidylcholine vesicles. P17 does not bind to negatively charged membranes composed of 1-palmitoyl-2-oleoyl-phosphatidylglycerol and 1-palmitoyl-2-oleoyl-phosphatidylcholine. Our differential scanning calorimetry results reveal that P17 slightly perturbs the phase behaviour of neutral phosphatidylcholine and negatively charged multilamellar vesicles. In contrast, the phase transition temperature of positively charged dimyristoylphosphatidylcholine/sphingosine multilamellar vesicles (molar ratio 9 : 1, respectively) is increased by approximately 2.4 C and the half width of the enthalpy peak broadened from 1.9 to 5.6 C in the presence of P17 (protein : lipid molar ratio 1 : 47). Moreover, the enthalpy peak is asymmetrical, suggesting that lipid phase separation is induced by P17. Based on the far-UV CD spectra, the ,-helicity of P17 increases upon binding to positively charged micelles composed of Triton X-100 and sphingosine. We propose that P17 can interact with positively charged lipid membranes and that this binding induces a structural change on P17 to a more tightly packed and ordered structure. [source]


    Annealing-Free High Efficiency and Large Area Polymer Solar Cells Fabricated by a Roller Painting Process

    ADVANCED FUNCTIONAL MATERIALS, Issue 14 2010
    Jae Woong Jung
    Abstract Polymer solar cells are fabricated by a novel solution coating process, roller painting. The roller-painted film , composed of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) , has a smoother surface than a spin-coated film. Since the roller painting is accompanied by shear and normal stresses and is also a slow drying process, the process effectively induces crystallization of P3HT and PCBM. Both crystalline P3HT and PCBM in the roller-painted active layer contribute to enhanced and balanced charge-carrier mobility. Consequently, the roller-painting process results in a higher power conversion efficiency (PCE) of 4.6%, as compared to that for spin coating (3.9%). Furthermore, annealing-free polymer solar cells (PSCs) with high PCE are fabricated by the roller painting process with the addition of a small amount of octanedi-1,8-thiol. Since the addition of octanedi-1,8-thiol induces phase separation between P3HT and PCBM and the roller-painting process induces crystallization of P3HT and PCBM, a PCE of roller-painted PSCs of up to 3.8% is achieved without post-annealing. A PCE of over 2.7% can also be achieved with 5,cm2 of active area without post-annealing. [source]