Stability constants and thermodynamic parameters of some intermacromolecular complexes in relation to their specific interaction forces

Summary Intermacromolecular complexes of poly (acrylic acid) (PAA) with poly (ethylene oxide) (PEO), poly (ethylene imine) (PEI) and poly (vinyl pyrrolidon) (PVP) were prepared. The stability constants and thermodynamic parameters (e.g. ΔH⁰ and ΔS⁰) of these complexes were determined at several temperatures. The enthalpy and entropy changes of the systems with temperature have been interpreted in terms of various mode of interaction between the components and compared with each other.     

The viscometric methods in the investigation of the polyacid-polybase interpolymer complexes

Two viscometric methods in the investigation of interpolymer complexes are presented. It has been shown that a presentation of the reduced viscosity ratio (experimental to ideal value) of a mixture of a polyacid with a nonionic polymer at constant total concentration as a function of the polymer mixture composition gives a better insight into the interpolymer association than a presentation of the specific viscosity at constant polyacid concentration as a function of the unit molar ratio. The formation of an expanded structure interpolymer complex is more easily revealed by the former procedure. © 1993 John Wiley & Sons, Inc.     

Electrochemical and spectroscopic studies of molybdenum(VI) complexes with aminopolycarboxylic acids

The complexes of molybdenum(VI) with iminodiacetic acid (IDA), nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic acid (EDTA) were investigated by means of polarographic and spectroscopic methods. The composition of the complexes was determined by the Job's method as following: 1Mo(VI)/1IDA; 1Mo(VI)/1NTA and 2Mo(VI)/1EDTA. The polarographic wave height was fairly dependent on the nature of the complexes. The overall reaction rate for the reduction of Mo(VI)-IDA complex was limited by diffusion. On the other hand, the polarographic reduction of Mo(VI)-NTA and - EDTA complexes were kinetically controlled by the preceding chemical reaction which was composed of protonation, dimerization and substitution of ligands, however, the rate-determining step was the substitution of ligands. The mechanism for the electroreduction of each complex was discussed.     

Stability constants and thermodynamic parameters of some intermacromolecular complexes of acrylic copolymers and poly(vinyl pyrrolidone)

Stability constants and thermodynamic parameters (e.g. ΔH⁰ and Δ⁰) have been determined for intermacromolecular complexes of methacrylic acid-methacrylamide and acrylic acid-acrylamide copolymers with poly(vinyl pyrrolidone) (PVP). The presence of nonionic units in the copolymers greatly enhances the stability of the complexes with PVP. The enthalpy and entropy changes of the systems with temperature have been interpreted in terms of various modes of interaction between the components.     

Electrochemical studies of the nickel catecholate complexes for detection of sulphur dioxide gas

Nickel catecholate complexes, bis(diphenylphosphino)ethanenickelcatecholate [(dppe)NiO₂C₆H₃4-R₁] R₁ = CH₃ (1), C(CH₃)₃ (2), H (3) and F (4)] were studied using CV and SWV techniques between −1.5 and +1.5 V at 50 mV s⁻¹ in cathodic and anodic sweeps. Glassy carbon electrode was used with 0.1 M tetrabutylammonium tetrafluroborate (TBATFB) in CH₂Cl₂. Complexes 1-4 before addition of SO₂, showed approximately reversible behaviour (i_pa/i_pc ≈ 1 and ΔE ≈ 77-88 mV); oxidation peaks observed between +313 and +524 mV, reduction peaks between +225 and +436 mV, depending on the substituent on the ligand. Detection limit 0.01 ppm, linear range 0.01-20 ppm, sensitivity 0.02 ppm/mV (with SWV) were obtained. The complexes 1 and 2 could be used as voltammetric sensors while complexes 3 and 4 would be suitable as amperometric sensors, for monitoring industrial SO₂ emissions.     

Ultrasonic and viscometric investigations of a poly(vinyl alcohol)–dextran mixture in aqueous solution

Ultrasonic spectroscopy provided a powerful, efficient, and reliable tool for a number of investigations, including those of polymer solution dynamics, molecular interaction, and the miscibility and compatibility of biopolymers in aqueous solutions. Ultrasonic velocity and related acoustic parameters were measured as a function of the concentration of poly(vinyl alcohol) (PVA), dextran, and a PVA–dextran mixture in water with the resonance method at a frequency of 3 MHz over a temperature range of 20–50°C. From the comparative results of sound velocity, density, adiabatic compressibility, acoustic impedance, and viscosity relaxation time as a function of temperature and concentration, the mode of interaction and the compatibility and miscibility between the two biologically active macromolecules were probed and were considerable at all concentrations and temperatures because of crosslinking via hydrogen bonding involving the hydroxyl groups of both of the biomacromolecules. The interpretations of the acoustic results were confirmed by the intrinsic viscosities of the ternary systems. The significant interaction and compatibility of these biopolymers should lead to the development of pharmaceutically active molecules. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3196–3201, 2003     

Metal-containing chemical fibres and their use in biotechnology

The possibility of using metal-containing fibres, including carbon fibres, as sorbents of proteins, viruses, and bacterial cells was demonstrated. It was found that silver-containing fibres can be effective adsorbents — carriers of Gluconobacter oxydans — a destroyer of thiodiglycol. Silver-containing fibres of different types exhibit bactericidal activity with respect to different bacterial cells; this activity is a function of the number and shape of the silver particles attached to the fibre. __________ Translated from Khimicheskie Volokna, No. 2, pp. 44–50, March–April, 2007.     

Recent Advances in Conjugated Transition Metal-containing Polymers and Materials

Metal-containing conjugated oligomers and polymers are reviewed, focusing on the work carried out by the author and coworkers since 1995. The synthesis of model systems, electropolymerizable monomers and polymer films are discussed, along with the electronic and spectroscopic properties of these systems. The application of phosphino-oligothiophene ligands as an entry to conjugated metallopolymers is described.     

Compatibility studies on solution of polymer blends by viscometric and phase‐separation technique

Solution blending of polystyrene (PS) and natural rubber (NR) was carried out in toluene and chloroform to determine the compatibility. Experimental evidence for the compatibility of these blends was derived from viscometric and phase‐separation studies. The viscometric method was based on the intrinsic viscosities of transfer of polymer in pure and “mixed” solvents. The compatibility of these blends based on the heat of mixing was also examined theoretically. All the experimental and theoretical evidence show that the blends are incompatible at the compositions studied. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 880–889, 2000     

Role of alkanols in micellar growth: A viscometric study

We have measured the viscosity of solutions of 0.3 M sodium dodecyl sulfate (SDS) + 0.3 M NaBr +n-alkanols as a function of [alkanol] and temperature. When propanol was added, the viscosity of micellar solutions remained almost constant and then decreased, whereas it continuously increased with hexanol. However, with butanol or pentanol, depending upon the added concentration, increases followed by decreases in viscosity were observed. This behavior has been discussed in light of solubility of alkanols in various soluble phases of the micellar system with a resultant change in the Mitchell-Ninham parameter of the “effective surfactant” (i.e., SDS +n-alkanol). An increase in temperature caused a decrease in viscosity, which is related to micellar breakdown. Activation parameters (ΔG* and ΔH*) were computed from the temperature dependence data. ΔH* Covered almost the total contribution to ΔG*.     

Electrochemical mass transfer studies in open cavities

Experimental measurements on free convection mass transfer in open cavities are described. The electrochemical deposition of copper at the inner surface of a cathodically polarized copper cylinder, open at one end and immersed in acidified copper sulphate was used to make the measurements. The effects on the rate of mass transfer of the concentration of the copper sulphate, the viscosity of the solution, the angle of orientation, and the dimensions of the cylinder were investigated. The data are presented as an empirical relation between the Sherwood number, the Rayleigh number, the Schmidt number, the angle of orientation and the ratio of the diameter to the depth of the cylinder. Comparison of the results with the available heat transfer data was not entirely satisfactory for a number of reasons that are discussed in the paper.Nomenclature C _b bulk concentration of Cu⁺⁺ (mol cm^–3) - C _b bulk concentration of H₂SO₄ (mol cm^–3) - C _o concentration of Cu⁺⁺ at cathode (mol cm^–3) - C _o concentration of H₂SO₄ at cathode (mol cm^–3) - D cavity diameter (cm) - D diffusivity of CuSO₄ (cm² s^–1) - D diffusivity of H₂SO₄ (cm² s^–1) - Gr Grashof number [dimensionless] (=Ra/Sc) - g acceleration due to gravity (=981 cm s^–2) - H cavity depth (cm) - h coefficient of heat transfer (Wm ^–2 K^–1) - i _L limiting current density (mA cm^–2) - K mass transfer coefficient (cm s^–1) - K ₁,K ₂ parameters in Equation 1 depending on the angle of orientation () of the cavity (see Table 3 for values) [dimensionless] - k thermal conductivity (W m^–1 K^–1) - L ^* characteristic dimension of the system (=D for cylindrical cavity) (cm) - m exponent on the Rayleigh number in Equation 1 (see Table 3 for values) [dimensionless] - Nu Nusselt number (=hL ^* k^–1) [dimensionless] - n exponent on the Schmidt number in Equation 1 (see Table 3 for values) [dimensionless] - Pr Prandtl number (=v/k) [dimensionless] - Ra Rayleigh number (defined in Equation 2) [dimensionless] - Sc Schmidt number (=v/D) [dimensionless] - Sh Sherwood number (=KD/D) [dimensionless] - ^t H⁺ transference number for H⁺ [dimensionless] - ^t Cu⁺⁺ transference number for Cu⁺⁺ [dimensionless] - specific densification coefficient for CuSO₄ [(1/)/C] (cm³ mol^–1) - specific densification coefficient for H₂SO₄ [(1/)/C] (cm³ mol^–1) - k thermal diffusivity (cm² s^–1) - dynamic viscosity of the electrolyte (g cm^–1 s^–1) - kinematic viscosity of the electrolyte (= /)(cm² s^–1) - density of the electrolyte (g cm^–3) - angle of orientation of the cavity measured between the axis of the cavity and gravitational vector (see Fig. 1) [degrees] - parameter of Hasegawaet al. [4] (=(2H/D))5/4 Pr^{– 1/2}) [dimensionless]     

Electrochemical removal of boron from water: Adsorption and thermodynamic studies

The present work provides an electrochemical removal of boron from water and its kinetics, thermodynamics, isotherm using mild steel and stainless steel as anode and cathode respectively. The various operating parameters on the removal efficiency of boron were investigated, such as initial boron ion concentration, initial pH, current density and temperature. The results showed that the optimum removal efficiency of 93.2% was achieved at a current density of 0.2 A dm^?2 at pH of 7.0. First‐, second‐order rate equations, Elovich and Intraparticle models were applied to study adsorption kinetics. Adsorption isotherms of boron on Fe(OH)₃ were determined and correlated with isotherm equations such as Langmuir, Freundlich and D‐R models. Thermodynamic parameters, such as standard Gibb's free energy (ΔG°), standard enthalpy (ΔH°) and standard entropy (ΔS°), were also evaluated by Van't Hoff equation. The adsorption process follows second‐order kinetics. The adsorption of boron preferably fits with Langmuir adsorption isotherm suggesting monolayer coverage of adsorbed molecules. The adsorption of boron onto Fe(OH)₃ was found to be spontaneous and endothermic. © 2011 Canadian Society for Chemical Engineering     

Electrochemical study of binary and ternary copper complexes in ammonia-chloride medium

Electrochemical and spectroscopic analyses (UV-vis and XRD) have been applied to evaluate the speciation of copper in ammonia-chloride solutions. The conditions for these analyses were established through thermodynamic studies that included predominance existence and E_h-pH diagrams. These studies highlighted the importance of copper ternary complexes and showed how the solubility of Cu(I) and Cu(II) increases over a wide range of pH when copper ternary complexes are formed. Hence, it has been elucidated the copper, ammonia and chloride concentrations that makes existence of these so-called copper ternary complexes, possible.     

Electrochemical behavior of amorphous carbon films: kinetic and impedance-spectroscopy studies

Impedance spectra and potentiodynamic curves of oxidation and reduction reactions in the quinone/hydroquinone and Ce^3+/4+ systems were measured in a 0.5M H₂SO₄ solution on amorphous carbon thin-film electrodes grown by magnetron sputtering or ion source techniques. The electrode equivalent circuit contains a constant phase element. Only narrow-bandgap (“graphitelike”) amorphous carbon is electrochemically active; however, the wider bandgap (“diamondlike”) material also acquires the activity on “doping” it with platinum (ca 10%) in the course of film growth. The admixture of platinum does not effect film conductivity; its action probably is of catalytic character. In its electrochemical activity, the platinum-containing amorphous diamondlike carbon films resemble boron-doped polycrystalline diamond.     

Electrochemical studies of titanium in fluoride-chloride molten salts

The interaction between titanium and Ti⁴⁺ ions (K₂TiF₆), the electroreduction reaction of Ti⁴⁺ ions and the anodic reaction of Ti in KCl–NaCl–KF melts with K₂TiF₆ at 973 K were studied by means of electrochemical and physical measurements. It was found that the fluoride ions played a very important role in these reactionsIn KCl–NaCl-3 wt % K₂TiF₆ molten salts with less than 3 wt % KF, the interaction reaction was considered to proceed as Ti⁴⁺+Ti=2Ti²⁺. If the bath contained more than 10 wt% KF, the reaction 3Ti⁴⁺+Ti=4Ti³⁺ occurred.The electrochemical reduction of Ti⁴⁺ (K₂TiF₆) ions in the molten salts with less fluoride ions was observed to proceed according to three reaction steps, i.e. Ti⁴⁺+e=Ti³⁺, Ti³⁺+e=Ti²⁺, Ti²⁺+2e=Ti. In the case of the fluoride ion concentration being higher, two reduction steps, i.e. Ti⁴⁺+e=Ti³⁺, Ti³⁺+3e=Ti were suggested.     

Electrochemical process for metal recovery from iodized silver derivatives in liquid/solid mixture: Experimental and theoretical approaches

This work examines the electrochemical behavior of “iodized silver derivatives,” pure or adsorbed on solid industrial wastes, in order to devise an electrochemical process for metal recovery from matrices containing these species. Voltammetric, coulometric and adsorption measurements were used to determine the reduction mechanism of silver derivatives at the electrode and to propose a reaction rate law depending on operating conditions.Mass balances and electrical balances of electrolyses of aqueous suspensions of solid wastes led to a better understanding and to the optimization of the overall electrochemical process of silver recovery. Comparison of experimental and theoretical results indicates the feasibility of the process proposed.     

Metal complexes of diisopropylthiourea: synthesis, characterization and antibacterial studies

Co(II), Cu(II), Zn(II) and Fe(III) complexes of diisopropylthiourea have been synthesized and characterized by elemental analyses, molar conductivity, magnetic susceptibility, FTIR and electronic spectroscopy. The compounds are non-electrolytes in solution and spectroscopic data of the complexes are consistent with 4-coordinate geometry for the metal(II) complexes and six coordinate octahedral for Fe(III) complex. The complexes were screened for their antibacterial activities against six bacteria: Escherichia coli, Pseudomonas auriginosa, Klebsiella pneumoniae, Bacillus cereus, Staphylococcus aureus and Bacillus pumilus. The complexes showed varied antibacterial activities and their minimum inhibitory concentrations (MICs) were determined.