Tunable viscosity modification with diluted particles: When particles decrease the viscosity of complex fluids

While spherical particles are the most studied viscosity modifiers, they are well known only to increase viscosities, in particular at low concentrations. Extended studies and theories on non-spherical particles find a more complicated behavior, but still a steady increase. Involving platelets in combination with complex fluids displays an even more complex scenario that we analyze experimentally and theoretically as a function of platelet diameter, to find the underlying concepts. Using a broad toolbox of different techniques we were able to decrease the viscosity of crude oils although solid particles were added. This apparent contradiction could lead to a wider range of applications.Comment: 13+7 pages, 6+7 figure

Micelles by self-assembling peptide-conjugate amphiphile: synthesis and structural characterization.

The solid-phase synthesis of a novel amphiphilic peptide conjugate I, contg. in the same mol. three different functions: N,N-bis[2-[bis(carboxyethyl)amino]ethyl]-L-glutamic acid chelating agent, the CCK8 bioactive peptide, and a hydrophobic moiety contg. four alkyl chains with 18 carbon atoms each, is reported. In water soln. at pH 7.4, I self-assembles in very stable micelles at very low concn. [crit. micellar concn. (cmc) values of 5 10-7 mol kg-1] as confirmed by fluorescence spectroscopy. The structural characterization, obtained with small-angle neutron scattering (SANS) measurements, indicates that the aggregates are substantially represented by ellipsoidal micelles with an aggregation no. of 39 2 and the two micellar axes of about 52 and 26

Polymerized mixed aggregates containing gadolinium complex and CCK8 peptide.

Two novel amphiphilic unimers contg. an aliph. hydrophobic chain (PDA) with two C C triple bonds and hydrophilic heads presenting the chelating agent DTPAGlu and the CCK8 bioactive peptide, resp., have been prepd. by solid phase synthesis. Aggregates obtained by mixing together PDA-DTPAGlu, or its Gd(III) complex, and PDA-L2-CCK8 in 70/30 molar ratio before and after a polymn. process carried out by UV irradn. have been structurally characterized by means of small angle neutron scattering. The relaxivity properties of aggregates contg. Gadolinium complexes have also been investigated. Elongated mixed micelles have been obsd., in which the relaxivity value r1p for each Gadolinium complex, measured at 20 MHz and 298 K, is around 12 mM-1s-1

Mutually Beneficial Combination of Molecular Dynamics Computer Simulations and Scattering Experiments

We showcase the combination of experimental neutron scattering data and molecular dynamics (MD) simulations for exemplary phospholipid membrane systems. Neutron and X-ray reflectometry and small-angle scattering measurements are determined by the scattering length density profile in real space, but it is not usually possible to retrieve this profile unambiguously from the data alone. MD simulations predict these density profiles, but they require experimental control. Both issues can be addressed simultaneously by cross-validating scattering data and MD results. The strengths and weaknesses of each technique are discussed in detail with the aim of optimizing the opportunities provided by this combination

Plait point in ternary system with a miscibility gap: Analysis of the procedures involved in its determination and development of novel procedures

Ternary miscibility data, usually reported in the Roozeboom triangular diagram, have been analyzed in Cartesian coordinates defined by X = (xi − xj)/√3 and Y = xk where xi, xj, and xk are the mole fractions of the two solvents and of the solute, respectively. This has allowed for an easy analytical representation of all the elements which are characteristic of the system: binodal curve, tie lines, plait point. Three novel methods for determining the plait point composition have been proposed based only on its fundamental properties. The results have been presented by applying the methods to some systems described in the literature. Differences between the values obtained with the proposed methods and those obtainable with the NRTL and UNIQUAC models have been found and are discussed

Interaction of poly(vinyl alcohol) with poly(acrylic acid) and with sodium polyacrylate in aqueous solutions: a volumetric study at 25° C.

The infinite dilution partial molar volumes of poly(acrylic acid), at different degrees of neutralization with sodium hydroxide, have been experimentally determined in aqueous solutions. Analysis of the data indicates that, the observed trend can be interpreted in terms of the electrostriction of the water molecules involved in the hydration cospheres of the carboxylic groups. The presence of PVA does not significantly affect the undissociated acid, but causes a large decrease for the sodium salt. This aspect has been discussed in terms of direct interaction between the two polymers