Physicochemical properties of anionic triple-chain surfactants in alkaline solutions

A series of novel gemini cationic surfactants alkanediyl-alpha,omega-bis (hydroxyethylmethylhexadecylammonium bromide) with polymethylene spacer chain length of 4, 6, 8, and 10 carbon atoms was synthesized and characterized. Critical micellar concentrations of the gemini surfactants in aqueous solutions as determined by the surface tension and conductance measurements were observed to be in the range 1.39-3.63 microM. The critical micellar concentration was observed to increase initially with spacer length up to 6 methylene groups and to decrease thereafter with the increase in spacer length. The micellar microstructure in aqueous solutions examined through small angle neutron scattering (SANS) revealed that the extent of aggregation growth and variation in shapes of micelles strongly depend on head group polarity, spacer chain length, and temperature. The propensity to micellar growth with spacer chain length 4 was found to be much higher than with the longer spacer lengths. The fractional charge on the micelle increases with increased spacer chain length and temperature.     

Physicochemical properties of aqueous solutions of dimethyl- and diethylsulfones

Aqueous solutions of dimethylsulfone (DMSO2) and diethylsulfone (DESO2) are studied by means of densimetry, surface tension, and calorimetry. The solution densities are defined and the apparent and partial molar volumes of DMSO2 and DESO2 are calculated in the temperature range of 293.15–323.15 K. It is revealed that in both cases the increase of sulfone concentration leads to the reduction of the surface tension. This is more expressed in the case of DESO2 than in the extension of the sulfone hydrocarbon chain. The calorimetric studies show that the dissolution enthalpies of DMSO2 and DESO2 do not differ substantially from one another; in both cases the dissolution of crystalline sulfones makes a crucial contribution to the enthalpy of dissolution values     

Physicochemical properties of aqueous solutions of L-aspartic acid containing chitosan

Physicochemical properties of aqueous solutions of L-aspartic acid with and without addition of chitosan have been studied by conductometry, potentiometry, refractometry, tensiometry, and viscosimetry. It has been shown that aspartic acid molecules take a cyclic configuration stabilized by hydrogen bonds in aqueous solution at c > 0.04 g/dL (298 K). The interaction of chitosan with aspartic acid results in the formation of the polymeric salt that dissociates in aqueous solution to give chitosan polycation [~(NH₃)⁺] and aspartate counterions. The addition of chitosan to solutions of L-aspartic acid results in progressive increase in the surface tension, absorbance, and refractive index as well as the change in hydrodynamic properties of the macromolecules. The polymeric salt exhibits polyelectrolyte properties in dilute aqueous solutions. The increase in temperature impairs the thermodynamic quality of the solvent for chitosan leading to the shrinkage of the polymer coils and, hence, to the decrease in the intrinsic viscosity of the system.     

Physicochemical and electrochemical properties of sulfolane solutions of lithium salts

The physicochemical and electrochemical properties (electrical conductivity, viscosity, density, and electrochemical stability) of sulfolane solutions of various lithium salts are studied. The nature of the anion considerably affects the physicochemical and electrochemical properties of the electrolyte systems considered. Sulfolane solutions of lithium salts have moderate electrical conductivity and high electrochemical stability, and can be used as electrolytes in lithium batteries.     

Physicochemical interaction in the system Si-Al-Ti-Ca-Mg-Fe-Na-K-O with the consideration of the formation of solid solutions

Based of a physicochemical model of basalt melting processes with the consideration of the solid solution formation, a method for determining the mineral compositions of gabbro-basalt rocks was proposed, which helps estimate the technological properties of melts for mineral fiber production and stone casting.     

Physicochemical properties of quercetin and rutin in aqueous solutions of decamethoxin antiseptic drug

The effect of a cationic surfactant, Decamethoxin, on the physicochemical properties of structurally related natural flavonoids, quercetin and rutin, was studied by spectrophotometry. The spectral and protolytic properties and the solubility of quercetin and rutin strongly depend on the Decamethoxin concentration in solution. The presence of Decamethoxin in the solution favors the tautomeric transition of the enol form of quercetin to the keto form.     

Physicochemical properties of low-dimension systems: Micellar solutions of surfactants and surfactant/polymer complexes

As shown in theoretical papers [1] and confirmed by experiments, the transport coefficients in micellar aqueous solutions exhibit a number of anomalies (minima and maxima in the concentration dependences). The studies revealed the existence of four critical micellization concentrations. At approximately 30°C, the critical micellization concentrations have a minimum. Measurements of the dynamic surface tension furnish information on surfactant/polymer complexation.     

Physicochemical properties of Cr/TiO2 solid solutions

Solid solutions of Cr³⁺ ions in TiO₂ have been prepared by impregnating commercial TiO₂ with CrO₃(aq) and annealing in O₂ at 770 K. X-Ray diffraction data show the absence of a segregated Cr₂O₃ phase. The magnetic and spectroscopic properties have also been investigated.

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Cr³⁺ TiO₂ TiO₂ CrO₃(.) O₂ 770 . Cr₂O₃. .

     

Physicochemical properties of the binary system glibenclamide and polyethylene glycol 4000

Solid dispersions of the antidiabetic drug glibenclamide and polyethylene glycol 4000 (macrogol 4000) were prepared by the melting method in order to increase the solubility of this poorly water-soluble compound. The temperature/composition phase diagram of the components was analyzed by hot-stage microscopy and differential scanning calorimetry, showing a monotectic. Polarized light hot stage microscopy and X-ray-powder diffraction confirmed, that glibenclamide is mainly present in a non-crystalline state after melting and solidifying of a 10% (w/w) mixture, which results in an enhanced solubility compared to physical mixtures. The solubility and dissolution rate of the drug increases clearly with decreasing drug/polymer ratio. Moreover, it was observed for the first time that a drug could crystallize as whiskers at the surface of aged solid dispersion particles. Besides relaxation phenomena, this crystallization mechanism may be responsible for a deterioration of liberation properties and bioavailability of solid dispersion based drug products with increasing storage time. This revised version was published online in July 2006 with corrections to the Cover Date.     

Solid clathrate solutions

The classification of solid clathrate solutions may be subdivided into three types: interstitial solutions, those with the substitution of one guest by another and those with the substitution of the particles in a host framework is given. All these types of solutions are illustrated by experimental (or computed) state diagrams of binary and ternary systems of guest-host and host-guest1-guest2 kinds, where host components are water, urea, thiourea and hydroquinone.     

The thermodynamic properties of spinel solutions in the Fe-Cu-O system

The activity of Fe₃O₄ in a spinel solution was calculated by direct processing of the experimental data on equilibrium between this solution and conjugated phases in the Fe-Cu-O system. The concentration dependence of the activity of Fe₃O₄ is discussed in terms of the theory of subregular ionic solutions.     

Physicochemical properties of eutonic aqueous solutions of zinc and copper tetraammoniates in the range 293–323 K

The density, viscosity, surface tension, and conductivity of subeutonic and eutonic solutions in the CuO-ZnO-NH₃-NH₄Cl-H₂O system at ammonia concentrations in the range 1.16–13.36 mol/l are determined experimentally in the temperature range 293–323 K. The expansion coefficient, the activation energy of viscous flow, the parachor, the orthochor, the degree of dissociation, and the equilibrium constant are calculated.     

Physicochemical processes in the nonequilibrium plasma-polymer system

The results of investigation into interaction between nonequilibrium plasma and polymers, including the mechanism of generation of active species in a direct-current discharge in oxygen, air, and oxygen mixtures with argon, are reported, and the formation behavior of gaseous products of the reactions of these species with polymer is discussed. The influence of the gaseous products on the physical characteristics of plasma and the rates of the processes involving electrons is considered.     

Physicochemical Modelling of Solid/Liquid Interfacial Phenomena

The proposed modelling of solid/liquid interfacial phenomena consists in relating the main experimental parameter – contact angle θ for metals or alloys on different substrates to combinations of the interatomic interaction parameters of the phases in contact. Physically, these interatomic interaction parameters are analogous to the electronic density distribution in the first and second coordination spheres of the crystallographic lattice of the component, to the bond length, and to the electrochemical factors. The contact angle θ of some alloys on AlN substrates in the case of non-reactive or reactive wetting is calculated.     

Physicochemical properties of nitrate aerosols: implications for the atmosphere

As aerosols, such as sea salt and mineral dust, are transported through the atmosphere they undergo heterogeneous reactions with nitrogen oxides to form nitrate salts. The nitrate salt can have quite different physicochemical properties than the original aerosol, resulting in an aerosol that will markedly differ in its climate impact, heterogeneous chemistry, and photoactivity. In this Feature Article, we will review some aspects of the importance of aqueous nitrate aerosols as well as describe a new multi-analysis aerosol reactor system (MAARS) that is used to measure the physicochemical properties of these atmospherically relevant aerosols. Here we show measurements of the hygroscopic properties, cloud condensation nuclei activity, and FTIR extinction of nitrate salt aerosol. In particular, we have measured the hygroscopic growth of 100 nm size-selected nitrate particles including NaNO3, Ca(NO3)2, Mg(NO3)2, and a 1:1 mixture of Ca(NO3)2 and Mg(NO3)2 as a function of relative humidity (RH) at 298 K. Using K?hler theory, we have quantified the water content of these particles with increasing RH. FTIR extinction measurements of the full size distribution of each of the nitrate aerosols are analyzed to yield information about the local solvation environment of the nitrate ions and the long-wavelength light scattering of the particles at different RH. Furthermore, we have measured and compared the cloud condensation nuclei (CCN) activity of CaCO3, a large component of mineral dust aerosol, and Ca(NO3)2, a product of atmospherically aged CaCO3 through reaction with nitrogen oxides, at supersaturations from 0.1% to 0.9%. These quantitative physicochemical data are needed if we are to better understand the chemistry as well as the climate effects of atmospheric aerosols as they are entrained, transported, reacted, and aged in the atmosphere. Our studies here focus on aqueous nitrate salts, the products of the reaction of nitrogen oxides with sea salt and mineral dust aerosol.     

Physicochemical Modelling of Solid/Liquid Interfacial Phenomena

Summary. The proposed modelling of solid/liquid interfacial phenomena consists in relating the main experimental parameter – contact angle θ for metals or alloys on different substrates to combinations of the interatomic interaction parameters of the phases in contact. Physically, these interatomic interaction parameters are analogous to the electronic density distribution in the first and second coordination spheres of the crystallographic lattice of the component, to the bond length, and to the electrochemical factors. The contact angle θ of some alloys on AlN substrates in the case of non-reactive or reactive wetting is calculated.     

Phase equilibria and the thermodynamic properties of spinel solutions in the Fe-Ti-O system

The activities of spinel solution components in the Fe-Ti-O system were calculated over the temperature range 1050–1600 K. The thermodynamic properties of the spinel solution were described using the model of subregular ionic solutions. The properties of the solution at low temperatures were predicted and the temperature of its stratification (957 ± 5 K) estimated.     

Physicochemical properties of multicomponent polyhydroxyalkanoates: Novel aspects

The physicochemical properties such as the degree of crystallinity and temperature and molecularmass characteristics of a number of polyhydroxyalkanoates of various chemical composition synthesized on a complex carbon substrate by bacteria Cupriavidus eutrophus В10646 have been investigated. Two-, three-, and four-component copolymer samples have different sets and ratios of monomers with various lengths of carbon chains: 3-hydroxybutyrate (3HB), 4-hydroxybutyrate (4HB), 3-hydroxyvalerate (3HV), 3-hydroxyhexanoate (3HH), 3-hydroxy-4-methyl valerate (3H4MV), and diethylene glycol (DEG). It has been shown that weight-average molar mass М _w and polydispersity vary in a wide range with no correlation existing with the composition of copolymer polyhydroxyalkanoates and that thermal stability is preserved in the temperature interval between the melting temperature and the thermal degradation temperature from 100 to 120–140°С. The composition and ratio of monomers most notably affect the degree of crystallinity of polyhydroxyalkanoates. Significant differences between the degrees of crystallinity of three- and four-component polyhydroxyalkanoates have been found for the first time. The degree of crystallinity for copolymers P(3HB/3HV/4HB) is 9–22%, and the degree of crystallinity for copolymers P(3HB/3HV/3HH) and P(3HB/3GV/3H4MV) is 41–63%; this value is close to the degree of crystallinity for diblock copolymers P(3HB)/DEG, which is 56–69%. For the four-component copolymers P(3HB/3GV/4HB/3HH), the degree of crystallinity is 30–41%. The values of М _w for the copolymers P(3HB/DEG) are inhomogeneous and the polymers contain fractions uneven with respect to molecular mass: a high-molecular-mass polymer (М _w from 2700 to 4900 kDa) and a low-molecular-mass polymer (М _w = 46–167 kDa). For the copolymers P(3HB)/DEG and P(3HB/3HV/3H4MV), two peaks are observed in the region of melting with the gap between these peaks being 4–20°С. All of the types of copolymer samples, regardless of the monomer ratio, show an increase in elongation at break against the background of a decrease in tensile stress and Young’s modulus, with these effects being pronounced to different extents. On the whole, the properties of multicomponent polyhydroxyalkanoates differ appreciably.