Search results for "Colloid"

Physico-chemical investigation of nanostructures in liquid phases: Nickel chloride ionic clusters confined in sodium bis(2-ethylhexyl) sulfosuccinate…

2009

The confinement of finite amounts of nickel chloride in the hydrophilic core of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles dispersed in n-heptane has been investigated by FT-IR, UV-vis-NIR and fluorescence spectroscopies. The analysis of experimental data consistently leads to hypothesize that NiCl(2) forms small size ionic clusters stabilized by a monolayer of oriented surfactant molecules. Due to confinement and interfacial effects, these ionic clusters show peculiar photophysical properties, which are different from those possessed by the bulk material. From NiCl(2)/AOT/n-heptane solutions, by evaporation of the organic solvent, interesting salt/surfactant nanocomposi…

N,N,N-Alkyloctyldimethylammonium Chlorides in Water: A Thermodynamic Investigation

1993

Abstract Specific conductivities, densities, heat capacities and enthalpies of dilution at 298 K and osmotic coefficients at 310 K were measured for N,N,N -octylbutyldimethylammonium, N,N,N -octylpentyldimethylammonium, and N,N -dioctyldimethylammonium chlorides in water as functions of concentration. From the specific conductivity data, the CMC and the degree of the counterion dissociation have been calculated. It is shown that additional CH 2 groups in the variable alkyl chain affect both CMC and β less than they do in the single chain surfactants. The partial molar volumes, heat capacities, relative enthalpies, nonideal free energies, and entropies at 298 K were derived as functions of t…

Modeling of Amino Acid Electrodiffusion through Fixed Charge Membranes

2001

Abstract We study theoretically the electrodiffusion of amino acids through fixed charge membranes, calculating the ionic fractions of the amino acid in the membrane as well as its total flux as a function of the relevant experimental parameters (amino acid concentration, salt concentration, and pH of the external solution; membrane fixed charge concentration; and amino acid membrane/solution partition coefficients) under different experimental conditions (symport vs antiport transport, uphill transport, etc.). The theoretical approach employed is based on the Nernst–Planck flux equations in the (Goldman) constant electric field assumption and considers all the species present in the system…

An On/Off Circular Dichroism Signal Reveals a pH Dependent Competition between a Cyclodextrin and a Polyelectrolyte for an Atropisomeric Aromatic Gue…

1997

Amphiphilic derivatives of a polyaspartamide: their aggregation and solubilization ability

2006

Abstract The self-aggregation and solubilization capability of a series of amphiphilic copolymers obtained by derivatisation of polymeric chain of α,β-poly(N-2-hydroxyethyl)- dl -aspartamide (PHEA) with polyethylene glycols (PEG, being different molecular weight 2000 or 5000 Da, PEG2000 and PEG5000, respectively) and/or hexadecylamine alkyl chain (C16), namely PHEA–PEG2000, PHEA–PEG5000, PHEA–C16, PHEA–PEG2000–C16 and PHEA–PEG5000–C16, have been evidenced by performing systematic tensiometric and spectrophotometric studies. All measurements have been performed at 25.0 °C over a wide copolymer concentration range. The tensiometric results have shown that, for all copolymers studied, the surf…

Optical tweezing electrophoresis of isolated, highly charged colloidal spheres

2001

Abstract We report on a novel optical tweezing experiment measuring the electrophoretic mobility μ of highly charged spherical particles suspended in water at volume fractions Φ≤2×10 −7 . At deionised conditions μ =2.5×10 −8 m 2 V −1 s −1 , it decreases further upon increasing the salt concentration c . We compare our data to measurements at larger Φ, where generally much larger μ and a qualitatively different dependence on the salt concentration are observed. To characterise the dependence on Φ we performed measurements at no added salt. There the mobility increases in the unordered state but stays constant at μ =6.8×10 −8 m 2 V −1 s −1 as the system develops fluid order. In the ordered re…

Polymer colloids II, Robert M. Fitch, Plenum, New York, 1980, 684 pp. Price: $69.50

1981

Polymeric janus particles.

2009

Since de Gennes' Nobel lecture in 1991, in which he coined the term "Janus grains", research into asymmetric particles has boomed. Macroscopic, microscopic and nanoscopic particles have been prepared in which certain parts of their surface differ in chemical composition, polarity, color, or any other property. Spherical, cylindrical, disc-like, snowman-, hamburger-, and raspberry-like structures have been synthesized from organic or inorganic materials or even as hybrids of both. Synthetic strategies towards such particles vary greatly from simple polymer mixtures to the bulk self-assembly of sophisticated terpolymers to immobilization methods of symmetric particles. Polymeric Janus particl…

Dye loading of amphiphilic poly(organosiloxane) nanoparticles.

2003

α,ω-Functionalized poly-N-isopropylacrylamides: controlling the surface activity for vesicle adsorption by temperature

2003

The synthesis of alpha,omega-end-functionalized copolymers of N-isopropylacrylamide and N-(3-dimethylaminopropyl)acrylamide was performed. Monomer ratios of 100:0, 96:4, and 81:19 were investigated. The lower critical solution temperature (LCST) of these polymers was determined by cloud-point measurements and by microcalorimetric measurements. The LCST increased from 32 over 37 to 47 degrees C as the hydrophobicity increased with increasing amount of comonomer N-(3-dimethylaminopropyl)acrylamide. The polymers could successfully be adsorbed onto gold surfaces. Finally, vesicle adsorption onto these self-assembled polymer films on flat gold surfaces was investigated as the vesicle solution te…