Structuring in solutions of polydiphenylenesulfophthalide salts and their combined systems with a cationic surfactant

New derivatives of polydiphenylenesulfophthalide, namely its alkali-metal salts and interpolymer complexes with a cationic surfactant, are prepared via polymer-analogous transformations. It is shown that, depending on the type of solvent, solutions of polydiphenylenesulfophthalide salts may feature the properties of polyelectrolytes or ionomers. On the basis of dynamic laser light scattering data, the sizes of associates formed in solutions of salts of polydiphenylenesulfophthalide and its complexes with cetyl pyridinium chloride are determined. With the use of dynamic drop tensiometry, the values of surface tension of the aqueous solutions of lithium polydiphenylenesulfophthalide and its complexes with cetyl pyridinium chloride, as well as viscoelastic characteristics of adsorption layers formed at the solution/air interface, are measured.     

Molecular structure and dynamics of poly(methacrylic acid) and poly(acrylic acid) complexes with dodecyl-substituted poly(ethylene glycol)

The molecular dynamics and the structure of molecular complexes formed by micelles of dodecyl-substituted poly(ethylene glycol) with poly(methacrylic acid) and poly(acrylic acid) in aqueous solutions were studied by viscosimetry, pH measurement, and electron spin resonance spin-probe techniques. At low surfactant concentrations, the conformation of the complex is a compact globule. The local mobility of surfactant molecules in such a complex is much slower than that in the free micelle. At high surfactant concentration, the nonionic micelles and polyacids form hydrophilic associates. The associates have the conformation of extended coils. In an associate, a major part of the micellar poly(ethylene glycol) groups is free. The local mobility of the micellar phase depends on the number of micelles involved in an associate. The mobility of surfactant molecules is slower in the complexes of poly(methacrylic acid) than in the complexes of poly(acrylic acid).     

Molecular Dynamics and Organization of Micellar Complexes of Poly(acrylic acid) with Poly(ethylene glycol)-Based Surfactants

The structure and molecular dynamics of complexes of poly(acrylic acid) with dodecyl-substituted poly(ethylene glycol)s in aqueous solutions are studied by viscometry and spin probe ESR spectroscopy. It is shown that, at low surfactant concentrations, the complexes have a compact globular conformation. The local mobility of the surfactant molecules in the complexes under consideration is much lower than their mobility in free micelles. As a result of increasing surfactant concentration in solution, the hydrophilic associates of the surfactant micelles with the polyacid having an unfolded coil conformation are formed. In an associate, a significant fraction of poly(ethylene glycol) fragments incorporated into micelles is in the free state, i.e., these fragments are not bound with a polymer chain. The local mobility of the surfactant molecules in the associate is considerably higher than in the complex with a compact conformation, and this mobility grows with the increasing number of micelles involved in the associate.     

Interaction of cationic monomer with sodium dodecyl sulfate in dilute aqueous solutions: ESR study

The effect of a cationic monomer (N,N,N,N-trimethyl[methacryloxyethyl]ammonium methyl sulfate) on the formation, structure, and local dynamics of associates resulted from the interaction of the monomer with sodium dodecyl sulfate in aqueous solutions was studied by ESR spectroscopy. In the presence of the monomer, micelles are formed at concentrations much lower than the CMC of the pure surfactant with the monomer molecules that form a condensed layer of counterions around a micelle of sodium dodecyl sulfate. The binding of surfactant micelles with the cationic monomer causes a significant decrease in the local molecular mobility of dodecyl sulfate ions.     

Synthesis and proton conductivity of adsorption-saturated and solvated porous hydroxyethylated cyclam layers on the surface of PVC-coated cellulose fabric

Porous layers of associates of adsorption-saturated and benzene- and hexane-solvated chloride and sulfate of hydroxyethylated cyclams with acid aqua complexes were synthesized on the surface of PVC-coated cellulose fabric. The porous structure of the layers includes a system of internal pores connected with the external pores via the diamine rings of the common walls of the hydroxyethylated cyclam nets; the internal pores are filled with the associates; the solvent molecules are adsorbed on the developed surface of the layers or solvate it. The H⁺ motion rate in a layer placed in solvent vapors or liquid solvents was measured; the layers were found to be nonlinear H⁺ conductors. The potential of H⁺ transition from the acid solution into the layer, the H⁺ mobility constant, and the field variation constant of the H⁺ mobility of the layer depend on the layer composition. The adsorption and solvation are accompanied by the formation of host-guest molecular complexes between the diamine rings of the cyclam nets and the benzene or hexane molecules, affecting the resistance of the associates to the incorporation of H⁺ ions and the H⁺ mobility in the associates.     

Activity coefficients and diffusion coefficients of dilute aqueous solutions of lithium,sodium, and potassium hydroxides

A simplified version of Harned's conductimetric technique has been used to measure binary diffusion coefficients of aqueous lithium, sodium, and potassium hydroxides at 25°C from 0.002 to 0.14 mol-dm^–3. Because of the large difference in mobility between OH^– and the cations, the electrophoretic effect tends to reduce the rate of diffusion of the alkali metal hydroxides; the largest effect is observed for LiOH solutions. The measured diffusion coefficients are in excellent agreement with predictions of the Onsager-Fuoss theory of ion transport. Precise activity coefficients determined from the diffusion measurements are compared with activity coefficients obtained previously by emf methods.     

Formation of triphenylmethyl radicals in the thermolysis of polydiphenylenesulfophthalide and polytriphenylcarbinol

Triphenylmethyl radicals are formed in the thermolysis of polytriphenylcarbinol and polydiphenylenesulfophthalide, which give rise to ESR singlets with poorly resolved hyperfine structure and two bands in the electronic absorption spectra.Institute of Organic Chemistry, Urals Branch, Russian Academy of Sciences, 450054 Ufa. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1682–1685, July, 1992.     

Effect of alkali metal hydroxides on the enantioseparation of amines using di-O-isopropylidene-keto-L-gulonic acid as the selector in NACE

The present work demonstrates the importance of the ionic composition in the BGE for enantioseparation. (-)-2,3:4,6-di-O-Isopropylidene-2-keto-L-gulonic acid ((-)-DIKGA) has been used as the chiral selector in methanolic and ethanolic BGEs. The influence of added alkali metal hydroxides on the EOF and the chiral separation of amines (atenolol, isoprenaline, pindolol and propranolol) have been studied. The ion-pair formation constants in ethanol were determined by precision conductometry for the enantiomers of pindolol with (-)-DIKGA, for Li(+), Na(+) and Cs(+) with (-)-DIKGA, and also for the corresponding alkali metal hydroxides. The effective mobilities and the enantiomeric mobility differences were affected by the type of alkali metal hydroxide (LiOH, NaOH, KOH, RbOH or CsOH) added to the BGE. The effective mobility and mobility difference were increased with decrease in solvated radius of the alkali metal cation. These differences could partly be correlated to the ion-pair formation constants of the alkali metal cations with the chiral selector, affecting the equilibrium concentration of the free selector. The electroosmosis was also affected by the alkali metal hydroxide added to the BGE. The cathodic electroosmosis decreased with decreasing solvated radius of the alkali metal cation added to the BGE. Interestingly, the cathodic EOF was even reversed, i.e. became anodic in the ethanolic BGEs containing KOH, RbOH or CsOH and the methanolic ones with RbOH and CsOH.     

Acid‐based approach for separation of peptide epimers using IM‐MS

Chiral molecules frequently remain undistinguishable using ion mobility mass spectrometry (IM‐MS), due to insufficient differences of their collision cross sections at the available mobility resolution of the ion mobility drift tubes. The influence of the complexation with organic acids on the ion mobility separation of peptide epimers is evaluated using traveling‐wave ion mobility (TWIMS). The examined epimeric tripeptides containing Arg residue with the sequence: Ac‐Phe‐Arg‐Trp‐NH₂ formed stable complexes in the gas phase, and under the increased pressure in ion mobility drift tube, noncovalent associates formed with carboxylic or sulfonic monoacids and diacids with chiral variation of certain acids. Overall, the complexation with an acid leads to the improvement in stereodifferentiation among epimeric peptides, in comparison to the analysis of pure epimers. Detailed characterization of peptide epimer‐acid associates obtained for dibenzoyl‐D‐tartaric acid by theoretical calculations and collisional dissociation studies revealed that the presence of multiple hydrogen bonding interactions between carboxylate anions and hydrogens from N―H of both the guanidinium group of arginine and the indole of tryptophan, as well as the amide backbone hydrogens in the peptide, is responsible for stability of acid‐peptide complexes and for their differentiation in the ion mobility drift tube. The specificity of complex formation toward Arg was determined in terms of complex stability. Based on the reported results, we present general conclusions regarding the utility of the acid‐based complexation in the separation of peptide isomers.     

High‐resolution quantification by charge‐dominant electrophoretic mobility shift of quantum dots

Conjugation of biomolecules to colloidal nanoparticles, such as quantum dots (QDs), often leads to change in mobility. We discover that linking DNA molecules to quantum dots alters their surface charge density without significantly increasing the hydrodynamic radius, causing a prominent shift in electrophoretic mobility. In this study, a high‐resolution molecular quantification method named quantification by QDs electrophoretic mobility shift (qQEMS) is developed based on the charge‐dominant transformation that closely associates DNA quantity to QDs electrophoretic mobility. The versatility of qQEMS is demonstrated by a number of quantification assays in which DNA molecules functioned as enzyme substrates, target‐specific probes, and competitive charge carriers. qQEMS shows a great potential as a generic and versatile quantification platform for a wide range of applications.     

A study of the local structure of aluminas obtained by different methods

The local structure of aluminas obtained from hydroxides (pseudo-boehmites) synthesized by different methods is studied using the radial density distribution function,. The occupancy of the cation sites of different types (tetrahedral and octahedral, spinel and non-spinel) in the structure of the studied oxides is analyzed.     

Solubilities of metal hydroxides

The solubilities of freshly precipitated and aged hydroxides of 21 metals have been calculated. The initial data set used for calculations comprised the stability constants and solubility products of hydroxides. The compositions and pHs of saturated solutions and the solubilities of hydroxides are dictated by the polarizing ability of charged metal atoms. The results of solubility calculations are in satisfactory agreement with experimental values.     

Effects of heavy metals and oxalate on the zeta potential of magnetite

Zeta potential is a function of surface coverage by charged species at a given pH, and it is theoretically determined by the activity of the species in solution. The zeta potentials of particles occurring in soils, such as clay and iron oxide minerals, directly affect the efficiency of the electrokinetic soil remediation. In this study, zeta potential of natural magnetite was studied by conducting electrophoretic mobility measurements in single and binary solution systems. It was shown that adsorption of charged species of Co(2+), Ni(2+), Cu(2+), Zn(2+), Pb(2+), and Cd(2+) and precipitation of their hydroxides at the mineral surface are dominant processes in the charging of the surface in high alkaline suspensions. Taking Pb(2+) as an example, three different mechanisms were proposed for its effect on the surface charge: if pH<5, competitive adsorption with H(3)O(+); if 56, precipitation of heavy metal hydroxides prevails. Oxalate anion changed the associated surface charge by neutralizing surface positive charges by complexing with iron at the surface, and ultimately reversed the surface to a negative zeta potential. Therefore the adsorption ability of heavy metal ions ultimately changed in the presence of oxalate ion. The changes in the zeta potentials of the magnetite suspensions with solution pH before and after adsorption were utilized to estimate the adsorption ability of heavy metal ions. The mechanisms for heavy metals and oxalate adsorption on magnetite were discussed in the view of the experimental results and published data.     

Standard systems for measurement of pKs and ionic mobilities. 1. Univalent weak acids

Determination of pK values of weak bases and acids by CZE has already attracted big attention in current practice and proved to offer the advantage of being applicable for mixtures of analytes. The method is based on the measurement of mobility curves plotting the effective mobility vs. the pH of the background electrolyte, and following computer-assisted regression involving corrections for ionic strength and temperature. To cover the necessary range of pH for a given case, both buffering weak acids and bases are used in one set of measurements, which requires implementing computations of individual ionic strength corrections for each pH value. It is also well known that some components of frequently used background electrolytes may interact with the analytes measured, on forming associates or complexes. This obviously deteriorates the reliability of the resulting data. This contribution brings a rational approach to this problem and establishes a standard system of anionic buffers for measurements of pKs and mobilities of weak acids, where the only counter cation present (besides H(+)) is Na(+). In this way, the risk of formation of complexes or associates of analytes with counter ions is strongly reduced. Moreover, the standard system of anionic buffers is selected in such a way that it provides, for an entire set of measurements, constant and accurately known ionic strength and the operational conditions are selected so that they provide constant Joule heating. Due to these precautions only one correction for ionic strength and temperature is needed for the obtained set of experimental data. This considerably facilitates their evaluation and regression analysis as the corrections need not be implemented in the computation software. The reliability and the advantages of the proposed system are well documented by experiments, where the known problematic group of phenol derivatives was measured with high accuracy and without any notice of anomalous behaviour.     

The effect of external orienting electric field on dielectric relaxation of segmented polyesters in dilute solution

A comparative study of dipole polarization relaxation in the absence and in the presence of an external orienting electric field was performed for linear segmented polyesters with alternating rigid (oxyfumaroylbis-4-oxybenzoates) and flexible (methylene-CH₂-, ethylene oxide-CH₂CH₂-O-, and dimethylsiloxane-Si(CH₃)₂-O-Si(CH₃)₂-) fragments in dilute solutions. Polyesters that do not display mesomorphic properties in the bulk show several regions of dielectric absorption with relaxation character. These regions are associated with the motions via the local mobility mechanisms of different polar fragments of the macromolecule. In solutions of polyesters that possess LC properties in the bulk, large-scale dipole polarization relaxation with long relaxation times and high activation energies was revealed along with local dielectric relaxation transitions. This process is associated with the cooperative motion of mesogenic fragments in their associates. In an external orienting electric field, the intensity of dielectric absorption usually increases for all types of dielectric transition; relaxation times and activation energies experience changes only for large-scale processes.     

Molecular mobility of a comb-shaped copolymethacrylate with chalcone chromophore-containing side groups

The molecular mobility of copolymethacrylate with chromophore-containing chalcone side chains is studied by broadband dielectric spectroscopy. Five regions of dipolar polarization relaxation are identified: namely, γ, β, β₁, α, and δ processes. It is shown that γ and β1 processes are related to the local mobility of methylene sequences and ester groups adjoining the backbone, while the α process is associated with the cooperative segmental mobility of the backbone. The β and δ processes are attributed to the mobility of chalcone groups: the local mobility in the glassy state (reorientation relative to the long axis of chromophores) and the cooperative mobility in the rubbery state (reorientation relative to the short axis of chromophores), respectively. The incorporation of 20% chalcone groups does not change the glass-transition temperature but enhances the cooperativity of the α process and intermolecular interactions.     

Long-term phosphorus effects on evolving physicochemical properties of iron and aluminum hydroxides

Iron (Fe) and aluminum (Al) hydroxides are highly reactive components in environmental processes, such as contaminant fate and transport. Phosphorus (P) sorption by these components can decrease environmental problems associated with excess accumulation of P in soils. The long-term stability of P sorbed by Fe/Al hydroxides is of major concern. Synthetic Fe and Al hydroxides coprecipitated with P (1:1 metal:P molar ratio) were incubated at 70 degrees C for 24 months to simulate natural long-term weathering processes that could influence the stability of sorbed P. Heat incubation (70 degrees C) of the untreated (no P) Al hydroxides resulted in drastic decreases (within the first month of incubation) in oxalate-Al extractability, specific surface area (SSA), and micropore volume with time. These changes were consistent with the formation of pseudoboehmite. Untreated Fe hydroxides showed no formation of crystalline components following heating (70 degrees C) for 24 months. Much smaller changes in oxalate-Al, P extractability, and SSA values were observed in the P-treated Al particles when compared with the untreated. Phosphorus treatment of both Fe and Al hydroxides stabilized the particle surfaces and prevented structural arrangements toward a long-range ordered phase. Slight reduction in SSA of the P-treated particles was related to dehydration phenomena during heating at 70 degrees C. Monitoring of physicochemical properties of the solids after heating at 70 degrees C for 2 years showed that sorbed P may be stable in the long-term. Understanding long term physicochemical properties may help engineers to optimize the Fe/Al hydroxides performance in several environmental/industrial applications.     

The relationship between thermodynamic properties and local atomic structure of Al-TM (TM = Mn,Fe, Co,Ni, Cu) melts

The relationship between structure and thermodynamic properties of Al- transition metal (TM) (TM = Mn, Fe, Co, Ni, Cu) melts had been studied by using the results of X-ray diffraction experiments, reverse Monte Carlo simulations and the model of ideal associated solution (MIAS). It was considered that local atomic structure of melts is determined by dense non-crystalline atomic packing and energy of interatomic interactions. This allowed to choose the types of associates for the MIAS. It is shown that the prominent role of the atomic packing factor in the Al-Mn, Al-Fe melts leads to correlation between the local atomic ordering of melts and the one of relevant polytetrahedral phases and defines a set of associates. Strengthening of heteroatomic interactions in the Al-Co, Al-Ni melts leads to an increase of the energy factor role in determining their structure and properties that reduces the number of associates from three for the Al-Mn melts to one for the Al-Ni.     

Association of macromolecules and its influence on polymer miscibility

Experimental data are shown which confirm the existence of increased macromolecules association in a polymer mixture. The increase of association is revealed in the increase of light scattering intensity and the increase of density (local ordering increase). The grown up association degree determines the peculiarities of network formation through cross-links in the solution of polymer mixtures. Macromolecules associates degrade under mechanical stresses or after addition of slight amounts of substances which are able to interact intensively intermolecularly (solvating) with macromolecules of one of the polymer components in the mixture. Representation of associates formation and degradation in polymer mixture help to explain many experimental data on thermodynamics, structure and properties of polymer mixtures.     

Synthesis and properties of long-chain quaternary ammonium hydroxides

A series of long-chain quaternary ammonium hydroxides were synthesized from tertiary amines and confirmed by ~1H NMR and FTIR.Surface properties and pH of these surfactants were investigated.The critical micelle concentrations(CMC) of the synthesized quaternary ammonium hydroxides are lower than the conventional quaternary ammonium surfactants.The micelles shapes of these long-chain quaternary ammonium hydroxides in aqueous solution are spherical at a concentration of 0.1 mol/L.The pH values of the synthesized quaternary ammonium hydroxides are 12.25-12.51.