Search results for "Colloid"
showing 10 items of 1288 documents
Kinetically Controlled Stepwise Self-Assembly of AuI-Metallopeptides in Water
2018
The combination of attractive supramolecular interactions of a hydrophobic AuI-metallopeptide with the shielding effect of flexible oligoethylene glycol chains provides access to a stepwise self-assembly of a AuI-metalloamphiphile in water. Kinetic control of the supramolecular polymer morphology is achieved using a temperature-dependent assembly protocol, which yields low dispersity supramolecular polymers (metastable state I) or helical bundled nanorods (state II).
Reactivity of lithium β‑ketocarboxylates: the role of lithium salts
2017
Lithium beta-ketocarboxylates 1(COOLi), prepared by the reaction of lithium enolates 2(Li+) with carbon dioxide, readily decarboxylate in THF solution unless in the presence of lithium salts, in which case they are indefinitely stable at room temperature in inert atmosphere. The availability of stable THF solutions of lithium beta-ketocarboxylates 1(COOLi) in the absence of carbon dioxide allowed reactions to take place with nitrogen bases and alkyl halides 3 to give alpha-alkyl ketones 1(R) after acidic hydrolysis. The sequence thus represents the use of carbon dioxide as a removable directing group for the selective monoalkylation of lithium enolates 2(Li+). The roles of lithium salts in …
Concerted Halogen-Bonded Networks with N-Alkyl Ammonium Resorcinarene Bromides: From Dimeric Dumbbell to Capsular Architectures
2015
N-Alkyl ammonium resorcinarene bromides and 1,4-diiodooctafluorobutane via multiple intermolecular halogen bonds (XB) form different exotic supramolecular architectures through subtle changes of the upper rim substituents. Dimeric dumbbell-like assembly with encapsulated guest molecules is generated with N-benzyl substituents. The N-hexyl groups engender an XB-induced polymeric pseudocapsule and an XB-induced dimeric capsule with entrapped 1,4-dioxane guest molecules. The N-propyl and N-cyclohexyl groups generate deep cavity cavitands. The deep cavity cavitands possess cavities for self-inclusion leading to polymeric herringbone arrangement in one direction and that pack into 3D polymeric a…
Free-Standing Mono layer Two-Dimensional Supramolecular Organic Framework with Good Internal Order
2015
Utilizing dynamic self-assembly and self-sorting to obtain large-area, molecularly precise monolayered structures represents a promising approach toward two-dimensional supramolecular organic frameworks (2D SOF) or 2D supramolecular polymers. So far, related approaches suffer from small domain sizes, fragility and weak long-range internal order. Here we report on the self-assembly of a host-guest enhanced donor-acceptor interaction, consisting of a tris(methoxynaphthyl)-substituted truxene spacer, and a naphthalene diimide substituted with N-methyl viologenyl moieties as donor and acceptor monomers, respectively, in combination with cucurbit[8]uril as host monomer toward monolayers of an un…
Solubilization by polysoaps
1994
The aqueous solubilization power of several series of micellar homopolymers and copolymers (''polysoaps'') is investigated. Using five insoluble or poorly water-soluble dyes, comparisons of the capacities are made with respect to the influence of structural variables such as the polymer backbone, the polymer geometry, the comonomer content, and the charge of the hydrophilic group. Some guidelines for polysoap structures suited for efficient solubilization are established. Noteworthy is that the solubilization capacities of the polysoaps are neither linked to the ability to reduce the surface tension of water, nor to the polarity of the solubilization sites deduced from spectroscopic probes.
Acid—base properties of azo dyes in the presence of surfactants
1991
Abstract The changes in the acid—base properties of an azo dye produced by the presence of surfactants, at surfactant concentrations below and above the CMC, are quantitatively described using a simple model and spectrophotometric and potentiometric measurements. The azo dye formed by aniline and N -(1-naphthyl)-ethylenediamine, and the surfactants sodium dodecyl sulphate, Triton X-100 and N -cetylpyridinium chloride (NCPC) are used. The protonation constants of the free and surfactant-bound dye species, the binding constant of the protonated and unprotonated forms of the dye, and the average aggregation number of the dye—NCPC aggregates are evaluated.
Structure and Shear Response of Janus Colloid–Polymer Mixtures in Solution
2020
We investigate the structure and rheological properties of dilute colloid-polymer mixtures at rest and under shear via molecular simulations that take into account hydrodynamic interactions. Mixtures of amphiphilic Janus colloids (JCs) and hydrophobic/amphiphilic polymers are considered for various solvent qualities and polymer concentrations. Free polymers, small polymer droplets, and hybrid aggregates coexist in mixtures with slightly hydrophobic homopolymers. As the solvent quality worsens, all polymers aggregate into small droplets, covered and stabilized by the JCs. In mixtures with amphiphilic polymers, we observe the coexistence of free polymers, purely polymeric micelles, and hybrid…
A synthetic hexapeptide (Argireline) with antiwrinkle activity
2008
Botulinum neurotoxins (BoNTs) represent a revolution in cosmetic science because of their remarkable and long-lasting antiwrinkle activity. However, their high neurotoxicity seriously limits their use. Thus, there is a need to design and validate non-toxic molecules that mimic the action of BoNTs. The hexapeptide Ac-EEMQRR-NH2 (coined Argireline) was identified as a result of a rational design programme. Noteworthy, skin topography analysis of an oil/water (O/W) emulsion containing 10% of the hexapeptide on healthy women volunteers reduced wrinkle depth up to 30% upon 30 days treatment. Analysis of the mechanism of action showed that Argireline significantly inhibited neurotransmitter relea…
Characterization of β-B-Agostic Isomers in Zirconocene Amidoborane Complexes
2009
The reaction of Cp(x)(2)ZrCl(2) (Cp(x) = Cp, Cp*) with ammonia borane in presence of n-butyllithium yielded Cp(2)Zr(Cl)NH(2)BH(3) and Cp(x)(2)Zr(H)NH(2)BH(3). These derivatives are isoelectronic with the ethyl zirconocene chloride and hydride, respectively, and feature a chelating amidoborane ligand coordinating through a Zr-N bond and a Zr-H-B bridge. In solution, each of the complexes consists of an equilibrium mixture of two isomers differing in the orientation of the amidoborane ligand with respect to the Zr-X bond (X = H, Cl), while in the solid state, only one isomer was observed. Such isomers have not been characterized for any metal complexes containing the isoelectronic beta-agosti…
Preparation and characterisation of Na 2 S and ZnSO 4 nanoparticles in water/sodium bis(2-ethylhexyl)sulphosuccinate/ n -heptane microemulsions
2001
The preparation procedure for nanoparticles of the water-soluble salts Na2S and ZnSO4, two commonly used reagents to synthesise ZnS nanoparticles, by evaporation of volatile components of salt-containing water-in-oil microemulsions is described. In suitable conditions, the evaporation leads to the formation of dry salt–surfactant composites and to the formation of Na2S or ZnSO4 nanoparticles. It was found that the salt–surfactant composites can be totally redissolved in a dry apolar organic solvent allowing the formation of virtually water-free solutions containing a considerable amount of the water-soluble salts. The presence of nanoparticles in these solutions and in the composites has be…