Temperature effect on the microstructure and viscoelastic properties of aqueous micellar systems of sodium <Emphasis Type="Italic">N</Emphasis>-methyl-<Emphasis Type="Italic">N</Emphasis>-oleyl taurate

The quantitative characteristics of the temperature effect on the rheological properties of aqueous solutions of the anionic surfactant sodium methyl oleyl taurate (SMOT) are presented. An increase in the intensity of thermal motion of surfactant molecules on heating from 25 to 45 °С was shown to decrease the average contour length of SMOT micelles from 2 μm to 700 nm. The decrease in the length of cylindrical micelles is probably one of the main reasons for a substantial decrease in the viscosity of micellar solutions of the surfactant with temperature.     

Effect of the Catalyst Nature on the Structure of Products of the Reaction of 4-(Dibromomethyl)Benzaldehyde with Trialkyl Orthoformates

Reactions of 4-(dibromomethyl)benzaldehyde with trialkyl orthoformates in the presence of both Brønsted (H₂SO₄) and Lewis (ZnCl₂) acids involved acetalization of the aldehyde group. In the first case, the corresponding acetal is formed as the only product, whereas in the second case the reaction is accompanied by transformation of the dibromomethyl group to give terephthalaldehyde and its mono- and bis-acetals.     

Reaction of Thiocarboxylic Acids with <Emphasis Type="Italic">N</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-Butyl-2-halo-2-methylpropanimines

Reaction of N-tert-butyl-2-chloro-2-methylpropanimine with thiocarboxylic acids has proceeded by two routes, one involving nucleophilic substitution of the chlorine atom in the primary iminium salt by acylthio group, and another via reduction of its cation at the C–Cl bond. Thiocarboxylic acids have reacted with 2-bromoaldimines only via reduction of primary salt cation at the C–Br bond. Acylthio-substituted iminium salts, aldehydes, and their acetals have been prepared.     

Reactions of diphenyldithiophosphinic acid with <Emphasis Type="Italic">N</Emphasis>-alkyl-2-chloro-2-methylpropanimines

In contrast to O,O-dialkyldithiophosphoric acids, the reactions of more weak diphenyldithiophosphinic acid with N-alkyl-2-chloro-2-methylpropanimines at a 1 : 1 reagent ratio follow two pathways. The first route is nucleophilic substitution of the chlorine atom of the initially formed iminium salt with the diphenylthiophosphinylthio moiety and the second route is the reduction of the C–Cl bond of this iminium salt cation. The main reaction direction is nucleophilic substitution producing new iminium salts, namely, N-alkyl-2-(di phenyl thiophosphinylthio)-2-methylpropaniminium chlorides. These salts were used as the starting material to synthesize new organophosphorus compounds bearing aldehyde, imine, and acetal groups and 1,3-diazolidine cycle.     

Aggregation behavior of morpholinium surfactants in the presence of organic electrolytes

It was shown that the addition of organic electrolytes to aqueous solutions of morpholinium surfactants facilitates micellization, reduces the micellar surface potential, increases the hydrodynamic diameter of micelles and favors the formation of cylindrical micelles which behave as pseudoplastic fluids. At low shear rates, the viscosity is extremely large and changes insignificantly, and it decreases sharply with increase in shear rate. Significant decrease in viscosity upon the increase in shear deformations indicates the orientation of cylindrical micelles along the direction of the flow with the increase in shear rate.     

Stochastic sensitivity analysis of the attractors for the randomly forced Ricker model with delay

Stochastically forced regular attractors (equilibria, cycles, closed invariant curves) of the discrete-time nonlinear systems are studied. For the analysis of noisy attractors, a unified approach based on the stochastic sensitivity function technique is suggested and discussed. Potentialities of the elaborated theory are demonstrated in the parametric analysis of the stochastic Ricker model with delay nearby Neimark–Sacker bifurcation.     

Mixed-mode self-oscillations,stochastic excitability,and coherence resonance in flows of highly concentrated suspensions

Nonlinear Dynamics - This article presents an overview of breaking waves and liquid sloshing impact acting on rigid walls and in liquid containers. The physics of breaking waves against rigid walls...     

On the theory of oscillating flows in complex liquids

Experiments with highly concentrated suspensions and other complex liquids frequently demonstrate nonmonotonic N- or S-shaped dependences of viscous stress σ on shear rate $ \dot \gamma $ \dot \gamma and strong oscillations of the shear rate at a constant flow-inducing external stress, as well as oscillations of the viscous stress at a constant average shear rate. A phenomenological mathematical model is proposed for oscillating flows according to which oscillations arise when an applied stress (or the average shear rate, depending on the design of an experiment) is in the descending region of the σ-$ \dot \gamma $ \dot \gamma dependence and a complex liquid exhibits pronounced viscoelastic properties.     

Temperature effect on the viscoelastic properties of solutions of cylindrical mixed micelles of zwitterionic and anionic surfactants

The viscoelastic properties of semidilute mixed aqueous solutions of oleyl amidopropylbetaine and sodium dodecylbenzene sulfonate are studied in the temperature range of 20–40°C. It is shown that, at 20°C, the solution viscosity can be as high as 390 (Pa s), which is related to the formation of a network of entanglements of long cylindrical micelles of surfactants. It is revealed that, upon heating, the viscosity and relaxation time of the system decrease, while the contour length of cylindrical micelles decreases consider-ably. It is shown that this susceptibility of viscoelastic surfactant solutions to temperature is due to the low energy of break, which is much lower than the energy of covalent bonds.     

Polyethylene glycol monomethyl ethers as the main component of brake fluid

The main physicochemical properties of polyethylene glycol monomethyl ethers in a wide temperature range were determined. The effect exerted on the main quality indices of brake fluids by the introduction of polyethylene glycol monomethyl ethers borates was studied. The use of these ethers as the main component of DOT-5.1 brake fluids was analyzed.