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Dganit Danino - One of the best experts on this subject based on the ideXlab platform.

  • Viscosity Peak due to Shape Transition from Wormlike to Disklike Micelles: Effect of Dodecanoic Acid
    Langmuir : the ACS journal of surfaces and colloids, 2018
    Co-Authors: Svetoslav E. Anachkov, Gergana Georgieva, Ludmila Abezgauz, Dganit Danino, Peter A. Kralchevsky
    Abstract:

    Here, we have investigated the synergistic growth of long wormlike micelles and their transformation into disklike micelles, which occurs in three-component solutions composed of sodium lauryl ether sulfate (SLES; anionic), cocamidopropyl betaine (CAPB; zwitterionic), and dodecanoic acid (HC12; nonionic). The solution rheology is characterized in terms of zero-shear viscosities and characteristic times for micellar breaking and reptation. Furthermore, the microstructure evolution, leading to the observed rheological behavior, is revealed by Cryo-Transmission Electron Microscopy (TEM) micrographs. In all cases, the CAPB-to-SLES ratio is fixed, whereas the fatty acid concentration is varied. At a certain HC12 concentration, the solution viscosity passes through a maximum. The cryo-TEM imaging indicates that wormlike micelles appear before the peak, grow further up to the peak, and finally transform into disklike aggregates (a very rare micellar structure) after the peak. The transformation of worms into dis...

  • structure and characterisation of hydroxyethylcellulose silica nanoparticles
    RSC Advances, 2018
    Co-Authors: Edward D H Mansfield, Dganit Danino, Yash Pandya, Ellina A Mun, Sarah E Rogers, Inbal Abutbulionita, Adrian C Williams, Vitaliy V Khutoryanskiy
    Abstract:

    Functionalising nanoparticles with polymers has gained much interest in recent years, as it aids colloidal stability and manipulation of surface properties. Here, polymer-coated thiolated silica nanoparticles were synthesised by self-condensation of 3-mercaptopropyltrimethoxysilane in the presence of hydroxyethylcellulose. These nanoparticles were characterised by dynamic light scattering, small angle neutron scattering, Nanoparticle Tracking Analysis, Raman spectroscopy, FT-IR spectroscopy, thermogravimetric analysis, Ellman's assay, transmission Electron Microscopy and Cryo-Transmission Electron Microscopy. It was found that increasing the amount of hydroxyethylcellulose in the reaction mixture increased the nanoparticle size and reduced the number of thiol groups on their surface. Additionally, by utilising small angle neutron scattering and dynamic light scattering, it was demonstrated that higher concentrations of polymer in the reaction mixture (0.5–2% w/v) resulted in the formation of aggregates, whereby several silica nanoparticles are bridged together with macromolecules of hydroxyethylcellulose. A correlation was identified between the aggregate size and number of particles per aggregate based on size discrepancies observed between DLS and SANS measurements. This information makes it possible to control the size of aggregates during a simple one-pot synthesis; a prospect highly desirable in the design of potential drug delivery systems.

  • Viscosity Peak due to Shape Transition from Wormlike to Disklike Micelles: Effect of Dodecanoic Acid
    2018
    Co-Authors: Svetoslav E. Anachkov, Ludmila Abezgauz, Dganit Danino, Gergana S. Georgieva, Peter A. Kralchevsky
    Abstract:

    Here, we have investigated the synergistic growth of long wormlike micelles and their transformation into disklike micelles, which occurs in three-component solutions composed of sodium lauryl ether sulfate (SLES; anionic), cocamidopropyl betaine (CAPB; zwitterionic), and dodecanoic acid (HC12; nonionic). The solution rheology is characterized in terms of zero-shear viscosities and characteristic times for micellar breaking and reptation. Furthermore, the microstructure evolution, leading to the observed rheological behavior, is revealed by Cryo-Transmission Electron Microscopy (TEM) micrographs. In all cases, the CAPB-to-SLES ratio is fixed, whereas the fatty acid concentration is varied. At a certain HC12 concentration, the solution viscosity passes through a maximum. The cryo-TEM imaging indicates that wormlike micelles appear before the peak, grow further up to the peak, and finally transform into disklike aggregates (a very rare micellar structure) after the peak. The transformation of worms into disks leads to a drop in viscosity because the length-to-thickness aspect ratio of the disks is significantly lower than that of the worms. In this article, we elucidate the structure–rheology relations in micellar solutions that might be applied for the design of personal-care and household formulations

  • sponge phases and nanoparticle dispersions in aqueous mixtures of mono and diglycerides
    Langmuir, 2016
    Co-Authors: Maria Valldeperas, Dganit Danino, Tommy Nylander, Malgorzata Wiśniewska, Maor Ramon, Ellina Kesselman, Justas Barauskas
    Abstract:

    The lipid liquid crystalline sponge phase (L3) has the advantages that it is a nanoscopically bicontinuous bilayer network able to accommodate large amounts of water and it is easy to manipulate due to its fluidity. This paper reports on the detailed characterization of L3 phases with water channels large enough to encapsulate bioactive macromolecules such as proteins. The aqueous phase behavior of a novel lipid mixture system, consisting of diglycerol monooleate (DGMO), and a mixture of mono-, di- and triglycerides (Capmul GMO-50) was studied. In addition, sponge-like nanoparticles (NPs) stabilized by Polysorbate 80 (P80) were prepared based on the DGMO/GMO-50 system, and their structure was correlated with the phase behavior of the corresponding bulk system. These NPs were characterized by dynamic light scattering (DLS), Cryo-Transmission Electron Microscopy (Cryo-TEM) and small angle X-ray scattering (SAXS) to determine their size, shape, and inner structure as a function of the DGMO/GMO-50 ratio. In addition, the effect of P80 as stabilizer was investigated. We found that the NPs have aqueous pores with diameters up to 13 nm, similar to the ones in the bulk phase.

  • structure and dynamics of poly oxyethylene cholesteryl ether wormlike micelles rheometry saxs and cryo tem studies
    Langmuir, 2011
    Co-Authors: Rekha Goswami Shrestha, Ludmila Abezgauz, Dganit Danino, Kenichi Sakai, Hideki Sakai, Masahiko Abe
    Abstract:

    In this article, we provide direct evidence for 1-D micellar growth and the formation of a network structure in an aqueous system of poly(oxyethylene) cholesteryl ether (ChEO20) and lauryl diethanolamide (L-02) by rheometry, small-angle X-ray scattering (SAXS), and Cryo-Transmission Electron Microscopy (cryo-TEM). The ChEO20 self-assembles into spheroid micelles above the critical micelle concentration and undergoes a 1-D microstructural transition upon the incorporation of L-02, which because of its lipophilic nature tends to be solubilized into the micellar palisade layer and reduces the micellar curvature. The elongated micelles entangle with each other, forming network structures of wormlike micelles, and the system shows viscoelastic properties, which could be described by the Maxwell model. A peak observed in the zero-shear viscosity (η0) versus L-02 concentration curve shifted toward higher L-02 concentrations and the value of maximum viscosity (η0 max) increased with the increasing ChEO20 mixing f...

Yeshayahu Talmon - One of the best experts on this subject based on the ideXlab platform.

  • Fluorophilic–Lipophilic–Hydrophilic Poly(2-oxazoline) Block Copolymers as MRI Contrast Agents: From Synthesis to Self-Assembly
    2018
    Co-Authors: Leonid I. Kaberov, Yeshayahu Talmon, Richard Hoogenboom, Bart Verbraeken, Anna Riabtseva, Jiri Brus, Petr Stepanek, Aurel Radulescu, Sergey K. Filippov
    Abstract:

    This work focuses on the synthesis and self-assembly of triphilic poly­(2-oxazoline) triblock copolymers with high fluorine content toward our future aim of developing poly­(2-oxazoline) magnetic resonance imaging (MRI) contrast agents. A highly fluorinated 2-substituted-2-oxazoline monomer, namely 2-(1H,1H,2H,2H-perfluorooctyl)-2-oxazoline, was synthesized using the Grignard reaction. The polymerization kinetics of the synthesized monomer was studied, and it was used for the preparation of triblock copolymers with hydrophilic 2-methyl-2-oxazoline, hydrophobic 2-octyl-2-oxazoline, and fluorophilic blocks by cationic ring-opening polymerization yielding polymers with low relatively dispersity (1.2–1.4). The presence of the blocks with the different nature in one copolymer structure facilitated self-assembly of the copolymers in water and dimethyl sulfoxide as observed by dynamic light scattering, Cryo-Transmission Electron Microscopy, and small-angle neutron scattering. The nanoparticle morphology is strongly influenced by the order and length of each block and the nature of solvent, leading to nanoparticles with core–shell structure as confirmed by small-angle neutron scattering. The reported poly­(2-oxazoline) block copolymers with high fluorine content have high potential for future development of MRI contrast agents

  • imaging the volume transition in thermosensitive core shell particles by cryo transmission Electron Microscopy
    Langmuir, 2006
    Co-Authors: Jerome J Crassous, Judith Schmidt, Matthias Ballauff, Markus Drechsler, Yeshayahu Talmon
    Abstract:

    We report a study of colloidal thermosensitive core−shell particles by Cryo-Transmission Electron Microscopy (cryo-TEM). The particles consist of a solid core of poly(styrene), onto which a network of cross-linked poly(N-isopropylacrylamide) (PNIPAM) is affixed. In water, the shell of these particles swells when the temperature is low. Raising the temperature above 32 °C leads to a marked shrinking of the shell. In this letter, we present the first study of these core−shell particles by cryo-TEM in situ, that is, in aqueous solution. We demonstrate that the core−shell particles are well-defined and exhibit a narrow size distribution. In particular, the PNIPAM shell is compact and has a defined outer surface of a slightly irregular shape. The micrographs show that there are density fluctuations within the network. Cryo-TEM of the system above and below the transition temperature furnishes information about the thermosensitive particles that had not been available through other methods employed in previous ...

  • self assembly of model collagen peptide amphiphiles
    Langmuir, 2001
    Co-Authors: Tushar Gore, And Matthew Tirrell, Yeshayahu Talmon, Yoav Dori, Havazelet Biancopeled
    Abstract:

    We have used Cryo-Transmission Electron Microscopy (cryo-TEM), small-angle neutron scattering (SANS), differential scanning calorimetry (DSC), and circular dichroism (CD) for microstructural characterization of amphiphiles that have a model collagen peptide headgroup. Single-tail amphiphiles and double-tail amphiphiles with short tails such as C12 and C14 formed spheroidal micelles. Further increase in tail length of the double-tail amphiphiles led to the formation of disklike micelles that aggregated to form a strandlike structure. SANS curves for double-tail amphiphiles were obtained at different contrasts by using different fractions of D2O in the D2O/H2O mixture. SANS data analysis using the sphere method confirmed the structures imaged by cryo-TEM and provided a detailed structural characterization. CD data showed that the peptide's capacity to organize into a triple helix by intertwining with two neighboring molecules can be affected by increasing the tail length. Double-tail amphiphiles with tails ...

  • cryo tem and nmr studies of a micelle forming phosphoglucolipid from membranes of acholeplasma laidlawii a and b
    Chemistry and Physics of Lipids, 1997
    Co-Authors: Dganit Danino, Alon Kaplun, Goran Lindblom, Leif Rilfors, Greger Oradd, Jon Hauksson, Yeshayahu Talmon
    Abstract:

    Abstract The chemical structure of a phosphoglucolipid from the membrane of the bacterium Acholeplasma laidlawii strain B-PG9 has been determined by high resolution NMR to be 1,2-diacyl-3-O-[glycerophosphoryl-6-O-(α- d -glucopyranosyl-(1→2)-O-α- d -glucopyranosyl)]-sn-glycerol (GPDGlcDAG). It was concluded that this lipid has exactly the same structure as one of the phosphoglucolipids from A. laidlawii strain A-EF22. By cryo transmission Electron Microscopy (cryo-TEM) and NMR diffusion techniques it was shown that, in highly diluted aqueous solutions, this membrane lipid forms long thread-like micelles in equilibrium with lipid vesicles. The cause of the occurrence of these different aggregates is discussed in terms of the varying molecular shapes of the lipid because of a heterogeneous composition of the acyl chains. A second membrane phosphoglucolipid from the bacterium, namely 1,2-diacyl-3-O-[glycerophosphoryl-6-O-(α- d -glucopyranosyl-(1→2)-monoacylglycerophosphoryl-6-O-α- d -glucopyranosyl)]-sn-glycerol (MABGPDGlcDAG), was found to form only a lamellar liquid crystalline phase coexisting with water.

  • on the structure of aggregated kappa carrageenan helices a study by cryo tem optical rotation and viscometry
    International Journal of Biological Macromolecules, 1996
    Co-Authors: Johan Borgstrom, Lennart Piculell, Christer Viebke, Yeshayahu Talmon
    Abstract:

    Abstract Cryo-Transmission Electron Microscopy (cryo-TEM), viscometry and optical rotation have been used to study the microstructure of dilute solutions of helical κ-carrageenan under varied electrolyte composition (0.1 M of NaI, CsI and mixtures of the two salts). Microfibers (300–400 nm in length) were observed above a critical cesium content, while below that no microstructure was seen in the micrographs. A drastic increase in the specific viscosity and an onset of thermal hysteresis in the optical rotation above the same critical cesium content provide clear evidence of aggregate formation. This leads to the conclusion that the observed microfibers are aggregates consisting of several helices. At high proportions of cesium, further aggregation of the microfibers was observed by cryo-TEM.

Katarina Edwards - One of the best experts on this subject based on the ideXlab platform.

  • A T-shaped amphiphilic molecule forms closed vesicles in water and bicelles in mixtures with a membrane lipid.
    The Journal of Physical Chemistry B, 2012
    Co-Authors: Peggy Scholtysek, Katarina Edwards, Anja Achilles, Claudia-viktoria Hoffmann, Bob-dan Lechner, Annette Meister, Carsten Tschierske, Kay Saalwächter, Alfred Blume
    Abstract:

    The T-shaped amphiphilic molecule A6/6 forms a columnar hexagonal liquid-crystalline phase between the crystalline and the isotropic liquid when studied in bulk (Chen et al., 2005). Because of the hydrophilic and flexible oligo(oxyethylene) side chain terminated by a 1-acylamino-1-deoxy-d-sorbitol moiety attached to a rigid terphenyl core with terminal hexyloxy alkyl chains, it was expected that also formation of lyotropic phases could be possible. We therefore studied the behavior of A6/6 in water and also in mixtures with bilayer-forming phospholipids, such as dipalmitoyl-phosphatidylcholine (DPPC), using differential scanning calorimetry (DSC), transmission Electron Microscopy (TEM), Cryo-Transmission Electron Microscopy (cryo-TEM), dynamic light scattering (DLS), and solid-state nuclear magnetic resonance (ssNMR). DSC showed for the pure A6/6 suspended in water a phase transition at ca. 23 °C. TEM and cryo-TEM showed vesicular as well as layered structures for pure A6/6 in water below and above this p...

  • melittin lipid interaction a comparative study using liposomes micelles and bilayer disks
    Biochimica et Biophysica Acta, 2008
    Co-Authors: Anna Lundquist, Per Wessman, Adrian R Rennie, Katarina Edwards
    Abstract:

    Comparison of melittin interaction with liposomes, bilayer disks and micelles showed that melittin binding to lipid aggregates is largely dictated by the amount of highly curved areas in the aggregates. The PEG-stabilised bilayer disks were characterised by a combination of small angle neutron scattering, Cryo-Transmission Electron Microscopy and dynamic light scattering. Importantly, the theoretically foreseen partial segregation of the lipid components, important for maintaining the structure of the bilayer disk, was confirmed. Steady state fluorescence spectroscopy indicated that melittin mainly resides at the rim of the bilayer disks. Results of the present study help increase the understanding of the mechanisms behind, and the physico-chemical factors affecting, melittin-lipid interaction. We suggest that bilayer disks, due to their stable structure, constitute interesting vehicles for transport of peptides that have high propensity to associate with lipid surfaces of high curvature.

  • morphological changes induced by phospholipase c and by sphingomyelinase on large unilamellar vesicles a cryo transmission Electron Microscopy study of liposome fusion
    Biophysical Journal, 1997
    Co-Authors: Gorka Basanez, M B Ruizarguello, Alicia Alonso, Felix M Goni, Goran Karlsson, Katarina Edwards
    Abstract:

    Cryo-Transmission Electron Microscopy has been applied to the study of the changes induced by phospholipase C on large unilamellar vesicles containing phosphatidylcholine, as well as to the action of sphingomyelinase on vesicles containing sphingomyelin. In both cases vesicle aggregation occurs as the earliest detectable phenomenon; later, each system behaves differently. Phospholipase C induces vesicle fusion through an intermediate consisting of aggregated and closely packed vesicles (the "honeycomb structure") that finally transforms into large spherical vesicles. The same honeycomb structure is also observed in the absence of enzyme when diacylglycerols are mixed with the other lipids in organic solution, before hydration. In this case the sample then evolves toward a cubic phase. The fact that the same honeycomb intermediate can lead to vesicle fusion (with enzyme-generated diacylglycerol) or to a cubic phase (when diacylglycerol is premixed with the lipids) is taken in support of the hypothesis according to which a highly curved lipid structure ("stalk") would act as a structural intermediate in membrane fusion. Sphingomyelinase produces complete leakage of vesicle aqueous contents and an increase in size of about one-third of the vesicles. A mechanism of vesicle opening and reassembling is proposed in this case.

  • solubilization of nonionic monoalkyl amphiphile cholesterol vesicles by octyl glucoside cryo transmission Electron Microscopy of the intermediate structures
    Langmuir, 1996
    Co-Authors: M Seras, Katarina Edwards, Michel Ollivon, Mats Almgren, Goran Carlson, Sylviane Lesieur
    Abstract:

    The micellization by octyl glucoside (OG) of diglycerol hexadecyl ether−cholesterol (1:1 wt %) sonicated vesicles containing a small amount of dicetyl phosphate has been studied by quasielastic light scattering, turbidity measurement, and cryogenic transmission Electron Microscopy. By using a controlled environment vitrification system (CEVS), this last technique provides new information about the vesicle−micelle transition structures without introducing artifacts due to changes in temperature or saturation. The intermediate structures have been visualized as a function of increasing surfactant composition. In the 0−0.5 range of the OG to lipid molecular ratio in the aggregates, profound vesicle rearrangements, mainly fusion and deformation processes, occur. At higher OG concentrations, the vesicles significantly decrease in size and form clusters which originate from a dense precipitate and coexist with mixed micelles, the proportion of lamellar structures being progressively reduced in favor of micelliz...

  • aggregate structure in dilute aqueous dispersions of oleic acid sodium oleate and oleic acid sodium oleate egg phosphatidylcholine
    Langmuir, 1995
    Co-Authors: Katarina Edwards, Mats Silvander, G. Karlsson
    Abstract:

    Cryo-Transmission Electron Microscopy was used to investigate the aggregate structure in dilute aqueous samples of oleic acid, as a function of pH. At pH 10.7, where the fatty acid is almost completely deprotonated, the micrographs show spherical or cylindrical micelles depending on the concentration. Upon a decrease of the pH to values just above 9, formation of unilamellar vesicles is induced. With decreasing pH the vesicles show an increasing tendency to aggregate. At pH between 8 and 7, large clusters of aggregated vesicles coexist with dispersed nonlamellar, presumably inverted hexagonal structures. Further decrease in pH results in a complete transition into nonlamellar liquid-crystalline structures and finally to the formation of oil droplets. Addition of high concentrations of oleic acid to small unilamellar lecithin vesicles induces, at pH 7.4 and lower, clustering and formation of particles with nonlamellar structure. At high pH, on the other hand, oleic acid acts like a conventional cationic surfactant. With increasing fatty acid: lipid molar ratio both significant vesicle growth and finally lipid solubilization into mixed micelles are observed.

Ludmila Abezgauz - One of the best experts on this subject based on the ideXlab platform.

  • Viscosity Peak due to Shape Transition from Wormlike to Disklike Micelles: Effect of Dodecanoic Acid
    Langmuir : the ACS journal of surfaces and colloids, 2018
    Co-Authors: Svetoslav E. Anachkov, Gergana Georgieva, Ludmila Abezgauz, Dganit Danino, Peter A. Kralchevsky
    Abstract:

    Here, we have investigated the synergistic growth of long wormlike micelles and their transformation into disklike micelles, which occurs in three-component solutions composed of sodium lauryl ether sulfate (SLES; anionic), cocamidopropyl betaine (CAPB; zwitterionic), and dodecanoic acid (HC12; nonionic). The solution rheology is characterized in terms of zero-shear viscosities and characteristic times for micellar breaking and reptation. Furthermore, the microstructure evolution, leading to the observed rheological behavior, is revealed by Cryo-Transmission Electron Microscopy (TEM) micrographs. In all cases, the CAPB-to-SLES ratio is fixed, whereas the fatty acid concentration is varied. At a certain HC12 concentration, the solution viscosity passes through a maximum. The cryo-TEM imaging indicates that wormlike micelles appear before the peak, grow further up to the peak, and finally transform into disklike aggregates (a very rare micellar structure) after the peak. The transformation of worms into dis...

  • Viscosity Peak due to Shape Transition from Wormlike to Disklike Micelles: Effect of Dodecanoic Acid
    2018
    Co-Authors: Svetoslav E. Anachkov, Ludmila Abezgauz, Dganit Danino, Gergana S. Georgieva, Peter A. Kralchevsky
    Abstract:

    Here, we have investigated the synergistic growth of long wormlike micelles and their transformation into disklike micelles, which occurs in three-component solutions composed of sodium lauryl ether sulfate (SLES; anionic), cocamidopropyl betaine (CAPB; zwitterionic), and dodecanoic acid (HC12; nonionic). The solution rheology is characterized in terms of zero-shear viscosities and characteristic times for micellar breaking and reptation. Furthermore, the microstructure evolution, leading to the observed rheological behavior, is revealed by Cryo-Transmission Electron Microscopy (TEM) micrographs. In all cases, the CAPB-to-SLES ratio is fixed, whereas the fatty acid concentration is varied. At a certain HC12 concentration, the solution viscosity passes through a maximum. The cryo-TEM imaging indicates that wormlike micelles appear before the peak, grow further up to the peak, and finally transform into disklike aggregates (a very rare micellar structure) after the peak. The transformation of worms into disks leads to a drop in viscosity because the length-to-thickness aspect ratio of the disks is significantly lower than that of the worms. In this article, we elucidate the structure–rheology relations in micellar solutions that might be applied for the design of personal-care and household formulations

  • structure and dynamics of poly oxyethylene cholesteryl ether wormlike micelles rheometry saxs and cryo tem studies
    Langmuir, 2011
    Co-Authors: Rekha Goswami Shrestha, Ludmila Abezgauz, Dganit Danino, Kenichi Sakai, Hideki Sakai, Masahiko Abe
    Abstract:

    In this article, we provide direct evidence for 1-D micellar growth and the formation of a network structure in an aqueous system of poly(oxyethylene) cholesteryl ether (ChEO20) and lauryl diethanolamide (L-02) by rheometry, small-angle X-ray scattering (SAXS), and Cryo-Transmission Electron Microscopy (cryo-TEM). The ChEO20 self-assembles into spheroid micelles above the critical micelle concentration and undergoes a 1-D microstructural transition upon the incorporation of L-02, which because of its lipophilic nature tends to be solubilized into the micellar palisade layer and reduces the micellar curvature. The elongated micelles entangle with each other, forming network structures of wormlike micelles, and the system shows viscoelastic properties, which could be described by the Maxwell model. A peak observed in the zero-shear viscosity (η0) versus L-02 concentration curve shifted toward higher L-02 concentrations and the value of maximum viscosity (η0 max) increased with the increasing ChEO20 mixing f...

  • origins of the viscosity peak in wormlike micellar solutions 1 mixed catanionic surfactants a cryo transmission Electron Microscopy study
    Langmuir, 2009
    Co-Authors: Lior Ziserman, Ludmila Abezgauz, Ory Ramon, Srinivasa R Raghavan, Dganit Danino
    Abstract:

    The rheology of wormlike micelles (“worms”) formed by surfactants in water often follows nonmonotonic trends as functions of composition. For example, a study by Raghavan et al. (Langmuir 2002, 18, 3797) on mixtures of the anionic surfactant sodium oleate (NaOA) and the cationic surfactant octyl trimethylammonium bromide (OTAB) reported a pronounced peak in the zero-shear viscosity η0 as a function of NaOA/OTAB ratio at a constant surfactant concentration (3 wt %). In this work, we study the origins of rheological changes in the NaOA/OTAB system and the relations between the composition and structural characteristics using Cryo-Transmission Electron Microscopy (cryo-TEM). When either surfactant is in large excess, the dominating morphology is that of spherical micelles. As oppositely charged surfactant is added to the mixture, the spheres grow into linear worms and these continue to elongate as the viscosity peak (which occurs at a 70/30 NaOA/OTAB ratio) is approached from either end. At the viscosity pea...

Judith Schmidt - One of the best experts on this subject based on the ideXlab platform.

  • imaging the volume transition in thermosensitive core shell particles by cryo transmission Electron Microscopy
    Langmuir, 2006
    Co-Authors: Jerome J Crassous, Judith Schmidt, Matthias Ballauff, Markus Drechsler, Yeshayahu Talmon
    Abstract:

    We report a study of colloidal thermosensitive core−shell particles by Cryo-Transmission Electron Microscopy (cryo-TEM). The particles consist of a solid core of poly(styrene), onto which a network of cross-linked poly(N-isopropylacrylamide) (PNIPAM) is affixed. In water, the shell of these particles swells when the temperature is low. Raising the temperature above 32 °C leads to a marked shrinking of the shell. In this letter, we present the first study of these core−shell particles by cryo-TEM in situ, that is, in aqueous solution. We demonstrate that the core−shell particles are well-defined and exhibit a narrow size distribution. In particular, the PNIPAM shell is compact and has a defined outer surface of a slightly irregular shape. The micrographs show that there are density fluctuations within the network. Cryo-TEM of the system above and below the transition temperature furnishes information about the thermosensitive particles that had not been available through other methods employed in previous ...

  • self assembly of model dna binding peptide amphiphiles
    Langmuir, 2005
    Co-Authors: Ronit Bitton, Judith Schmidt, Raymond S Tu, Matthew Tirrell, Markus Biesalski, Havazelet Biancopeled
    Abstract:

    Peptide amphiphiles combine the specific functionality of proteins with the engineering convenience of synthetic amphiphiles. These molecules covalently link a peptide headgroup, typically from an active fragment of a larger protein, to a hydrophobic alkyl tail. Our research is aimed at forming and characterizing covalently stabilized, self-assembled, peptide-amphiphile aggregates that can be used as a platform for the examination and modular design and construction of systems with engineering biological activity. We have studied the self-assembly properties of a model DNA-binding amphiphile, having a GCN4 peptide as the headgroup and containing a polymerizable methacrylic group in the tail region, using a combination of small-angle X-ray scattering, small-angle neutron scattering, and cryo- transmission Electron Microscopy. Our results reveal a variety of morphologies in this system. The peptide amphiphiles assembled in aqueous solution to helical ribbons and tubules. These structures transformed into la...

  • composite polymer nanofibers with carbon nanotubes and titanium dioxide particles
    Langmuir, 2005
    Co-Authors: Shahar Kedem, Judith Schmidt, Yaron Paz, Yachin Cohen
    Abstract:

    Composite nanofibers containing nanometric TiO2 particles and multiwalled carbon nanotubes dispersed in poly(acrylonitrile) (PAN) were prepared by the electrospinning technique. The structure and quality of the precursor dispersions were evaluated by Cryo-Transmission Electron Microscopy. The fabricated nanofibers, the diameters of which were in the 20−200 nm range, contained well-oriented nanotubes and spherical TiO2 nanoparticles in close proximity. Such nanofibers are under investigation as new photocatalytic reactor elements.