Aqueous Cholesteric Liquid Crystals Using Uncharged Rodlike Polypeptides

Bellomo, Enrico G.; Davidson, Patrick; Impéror‐Clerc, Marianne; Deming, Timothy J.

doi:10.1021/ja047932d

Cited by 38 publications

(35 citation statements)

References 28 publications

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“…The absorption of the supernatant at 422 nm was then compared to a linear calibration curve (Supporting Information) that had been obtained by reacting the TNBS dye with variable concentrations of free APS in water. We thus obtained an amine content of 0.43((0.06)% in the sample, suggesting that amine functionalities are present on 21 26 This supports the assumption that only the protonated sites can react with the silane agent. While it is difficult to assess the detailed binding geometry of the silanes, geometric considerations show that it is impossible for one silicon atom to simultaneously bind to more than one Nb-O site on the Ca 2 Nb 3 O 10 nanosheet.…”

Section: Resultssupporting

confidence: 73%

“…18,19 Due to their uniaxial geometry, these structures have one easy magnetic axis (see Figure 1A), which in the presence of an external magnetic field aligns with the field lines. 20,21 In contrast, magnetic structures with platelike morphology ( Figure 1B) can have multiple in-plane easy axes, which might enable magnetic manipulation of such structures in three dimensions with use of suitably oriented fields.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis and Real-Time Magnetic Manipulation of a Biaxial Superparamagnetic Colloid

et al. 2005

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Superparamagnetic colloidal plates were synthesized from tetrabutylammonium stabilized Ca 2 Nb 3 O 10 nanosheets and oleic acid-stabilized Fe 3 O 4 nanoparticles. Modification with 3-aminopropyltrimethoxysilane produces amine-terminated Ca 2 Nb 3 O 10 with an amine concentration of 0.43 ( 0.06 groups per Ca 2 Nb 3 O 10 unit as follows from spectroscopic quantification with trinitrobenzenesulfonic acid as a dye. Treatment of the modified sheets in THF/ethanol with 5.3 nm oleic acid-stabilized magnetite nanoparticles yields pseudo-2D assemblies that consist of 2 nm thick nanosheets decorated on both sides with a dense collection (9.3 ( 0.5 × 10 3 particles per square micrometer per side) of magnetite particles. In noncoordinating or weakly coordinating solvents, these composite particles further aggregate into stacked aggregates with a mean edge length of 1.6 ( 0.7 µm and a thickness of 79 ( 30 nm. The colloidal plates were characterized by elemental analysis, X-ray powder diffraction, and infrared and UV/vis spectroscopy. SQUID measurements show that films of the aligned particles are superparamagnetic at room temperature. The magnetic hysteresis that is observed at 5 K reveals that the plates have a magnetic anisotropy with the easy axis in the plane of the plates and the hard axis perpendicular to it. Calculations show that the magnetic anisotropy is a direct consequence of the two-dimensional distribution of the magnetic nanoparticles on the sheets. Optical microscopy reveals that when suspended in ethanol or THF, the colloidal plates can be rotated in real time with a variable external magnetic field (200 Oe). Magnetic alignment of the particles in suspensions also produces asymmetric light scattering patterns and magnetic birefringence. These effects and the observed magneto-orientational properties make the biaxial colloids interesting as components in displays and as magnetic actuators.

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Section: Resultssupporting

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Synthesis and Real-Time Magnetic Manipulation of a Biaxial Superparamagnetic Colloid

et al. 2005

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“…[243] A water-soluble polylysine was prepared by substitution with an oligoether side chain (78,Scheme 34). [249] The formation of a cholesteric phase in aqueous solution was determined by optical microscopy and X-ray scattering. A polyglutamate, a polylysine, and a polytyrosine all containing fluorescent carbazol groups were prepared (e.g.…”

Section: Liquid-crystalline Polypeptidesmentioning

confidence: 99%

Polypeptides and 100 Years of Chemistry of α‐Amino Acid N‐Carboxyanhydrides

2006

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Syntheses and polymerizations of alpha-amino acid N-carboxyanhydrides (NCAs) were reported for the first time by Hermann Leuchs in 1906. Since that time, these cyclic and highly reactive amino acid derivatives were used for stepwise peptide syntheses but mainly for the formation of polypeptides by ring-opening polymerizations. This review summarizes the literature after 1985 and reports on new aspects of the polymerization processes, such as the formation of cyclic polypeptides or novel organometal catalysts. Polypeptides with various architectures, such as diblock, triblock, and multiblock sequences, and star-shaped or dendritic structures are also mentioned. Furthermore, lyotropic and thermotropic liquid-crystalline polypeptides will be discussed and the role of polypeptides as drugs or drug carriers are reviewed. Finally, the hypothetical role of NCAs in molecular evolution on the prebiotic Earth is discussed.

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“…Smaller cells of average radius 3 mm and height 10 mm permit one to work with very small sample volumes (about 0.2 ml), which is particularly suited to the case of biological samples for example. 7 The measurement of the torque transferred by the sample to the inner cylinder is made using a force sensor at a distance of 20 mm from the rotation axis. The accessible torque range is from 10 -5 to 2×10 -2 Nm corresponding to a stress range from 1 to 2000 Pa.…”

Section: Custom Couette Apparatusmentioning

confidence: 99%

RheoSAXS studies of anisotropic complex fluids under shear

Silva¹,

Petermann²,

Kasmi³

et al. 2010

J. Phys.: Conf. Ser.

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Cylindrical intermediates in a shearinduced lamellar-to-vesicle transition J. Zipfel, F. Nettesheim, P. Lindner et al.Rheo-SAXS investigation of shear-thinning behaviour of very anisometric repulsive disc-likeclay suspensions A M Philippe, C Baravian, M Imperor-Clerc et al. Abstract. We discuss the application of in-situ rheological small angle X-ray scattering experiments to the study of complex fluids under shear, implemented using custom Couette cylinder rheometers mounted on the SWING beamline of the SOLEIL Synchrotron. We discuss several applications of this technique to the study of phase transitions in nanoparticle doped liquid crystals and shear alignment of clay suspensions. The concurrent capture of rheological and scattering data provides vital information that relates macroscopic properties such as viscosity to the microstructure of the fluid. IntroductionThe study of complex fluids and of their rheological properties is an active area of research with a wide range of applications.1 The bulk macroscopic properties of complex fluids, such as rheological properties such as shear viscosity, for example, will often depend on the structure of the fluid on a microscopic level. Thus it is often convenient to combine various techniques in order to study macroscopic and microscopic properties at the same time. Investigations using small angle scattering techniques (SAS) (light, neutrons, X-rays) can be performed on such fluids directly under flow; this allows the simultaneous recording of rheological quantities (such as flow-curves and viscosity profiles) and structural information. In the case of strongly anisotropic fluids, small angle X-ray or neutron scattering (SAXS/SANS) experiments are particularly well suited to following orientation phenomena of structured fluids under flow. Using new rheological small-angle (Rheo-SAXS) instruments developed at the SWING SAXS beamline of the SOLEIL synchrotron, we present some examples of results demonstrating in detail the behaviour under shear of doped surfactant lamellar phases and colloidal clay suspensions.

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Aqueous Cholesteric Liquid Crystals Using Uncharged Rodlike Polypeptides

Cited by 38 publications

References 28 publications

Synthesis and Real-Time Magnetic Manipulation of a Biaxial Superparamagnetic Colloid

Synthesis and Real-Time Magnetic Manipulation of a Biaxial Superparamagnetic Colloid

Polypeptides and 100 Years of Chemistry of α‐Amino Acid N‐Carboxyanhydrides

RheoSAXS studies of anisotropic complex fluids under shear

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