Micellar liquid chromatography for lipophilicity determination of new biologically active 1,3‐purinodiones

A series of newly synthesized 1,3‐purinodiones with potential anticonvulsant activity, exhibiting affinity to adenosine A₁ and/or A_2A receptors, were subjected to micellar LC (MLC) with SDS as micelle‐forming agent and n‐propanol as organic modifier. Two C18 silica‐based columns were employed in MLC: a particle one and a monolithic. In parallel, those derivatives were also analyzed in RP‐LC on four silica‐based columns and on an immobilized artificial membrane column. The correlations between the relevant logarithms of the retention factors of analytes obtained in MLC, immobilized artificial membrane and RP‐LC systems on the one hand, and the calculated log P (clog P) and log D values (clog D) on the other, were examined. The level of the correlations of retention data from MLC and RP‐LC systems with clog P and clog D obtained is similar but it could be stressed that MLC allows increasing the speed of analysis and using only one mobile phase. Moreover, there is no need of applying an extrapolation procedure in lipophilicity determination. Therefore, the MLC systems, providing chromatographic data in a fast and efficient manner, were demonstrated as promising alternatives to the classical RP‐LC systems to estimate the lipophilicity of drugs and drug candidates.     

Salting out of alcohols by alkali halides at the freezing temperature

The freezing-point depression of the ternary systems water-alkali halidesalcohols was measured with a precision Advanced Instrument osmometer. From the corresponding freezing-point depression of the binary systems the salting-out constantsk _s were calculated. The effect of ionic size was investigated withtert-butanol, and the effect of alcohol chain length with NaCl. The trends ofk _s with ionic size are similar to those of typical nonelectrolyte systems, andk _s varies linearly with the volumes of the normal alcohols.     

Development of novel cardo‐containing phenylethynyl‐terminated polyimide with high thermal properties

A phenylethynyl‐terminated reactive diluent [Card‐4‐phenylethynylphthalic anhydride (PEPA)], which contained fluorenyl cardo structures, was successfully synthesized and used as a modifier for flexible phenylethynyl‐terminated imide oligomer (PEI‐PEPA). The chemical structure, crosslink characterization, molecular weights, and thermal properties of the products were characterized. The imide systems with addition of 10, 20, 30, and 40 wt% Card‐PEPA to PEI‐PEPA (PEI‐PEPA‐Card) and their cured resin systems were prepared. The thermal curing behaviors of imide systems at different heating rates were analyzed by using differential scanning calorimetry. Thermal properties such as glass transition temperature (T_g) and char yield at 800°C of the resultant resin systems were studied by differential scanning calorimetry, dynamic mechanical analysis, and thermogravimetric analysis. The rheological properties were also investigated using a dynamic rheometry. These properties were found to be outstanding compared with pure PEI‐PEPA. The uncured imide systems exhibited lower T_g and lower isothermal viscosity with addition of Card‐PEPA. Furthermore, the T_g and char yield of the cured resin systems increased with addition of Card‐PEPA. The cured resin systems containing 40 wt% Card‐PEPA exhibited the highest T_g of 359°C and char yield at 800°C of 66.5%. Copyright © 2016 John Wiley & Sons, Ltd.     

Thermodynamic Analysis of Phase Separation of a Thermoplastic in the Precursors of Different Epoxy-Amine Systems

The miscibility of a thermoplastic, polystyrene (PS), with the precursors of several epoxy-amine systems has been studied thermodynamically and experimentally. The epoxy-amine systems were different only in the origin of amino groups, which were provided by a monoamine (MA) and a diamine (DA) in different proportions. Cloud-point curves (CPC) at conversion zero were reported for five modified systems with different MA-DA proportion. All CPCs showed an UCST behaviour. CPC shifted to lower temperatures when the ratio of MA/DA in the system increased, meaning that the MA produces an increase in the miscibility of the system. A model based on the Flory-Huggins theory was used for the thermodynamic analysis, in which the dependence of interaction parameter on temperature and composition, χ(T,ϕ), and the polydispersity of components were considered. A general equation for χ(T,ϕ) also depending on the MA-DA proportion was reached and used to obtain the phase diagram of the different systems. A high level of agreement between theoretical and experimental CPCs was obtained.     

Analytical possibilities of digital colorimetry: Determination of nitrite using polyurethane foam

Using the example of the determination of nitrite as polymeric azodye, the possibility of using office scanners, digital cameras, and computer data processing in different colorimetric coordinate systems (RGB, CMYK, LAB, and HSV) has been studied. Polymeric azodye was obtained by an azocoupling reaction between diazotized polyurethane foam (PUF) with 3-hydroxy-7,8-benzo-1,2,3,4-tetrahydroquinoline. The analytically important colorimetric coordinates in these systems were revealed and compared and the coordinates that result in the maximum sensitivity of nitrite determination were chosen. It was shown that calibration curves of the colorimetric coordinates versus concentration of nitrite in aqueous solution can be described by a first-order exponent. The detection limits of nitrite (1–3 ng/ml) were achieved in the RGB and CMYK colorimetric systems.     

Surface tension of binary and two ternary mixtures containing water–acetonitrile–methanol/ethanol at 298.15 K: experimental data,correlation and prediction by various models

Surface tension of two ternary mixtures of water/acetonitrile/methanol and water/acetonitrile/ethanol, and their constituent binaries, were measured over the whole range of composition at 298.15 K and ambient pressure. The experimental data were used to calculate in the surface tension deviations (Δσ). The negative values of Δσ for the binary and ternary systems indicate the strong hydrogen bonding between unlike molecules of mixtures (particularly in the high concentration of water). Surface tension data of the binary systems were correlated with Fu et al., Wang–Chen, Redlich–Kister and Myers–Scott models. The mean standard deviation obtained from the comparison of experimental and calculated surface tension values for binary systems with four models is less than 0.42. Finally, the concentration dependence of the surface tension deviation of the ternary mixtures at 298.15 K was correlated using Pando et al. and Ku et al. models, with satisfactory results.     

The influence of cross-linking agents on ring-opening metathesis polymerized thermosets

The addition of suitable cross-linking agents with norbornene-based monomers has significant effects on the thermal properties of the resulting polymers formed by olefin metathesis. Ethylidene norbornene (ENB) and endo-dicyclopentadiene (endo-DCPD) were mixed separately with various loadings of three different cross-linking agents and then polymerized with the addition of Grubbs’ catalyst. The polymerization kinetics and resulting glass transition temperature (T _g) of the systems were evaluated by differential scanning calorimetry (DSC). The addition of the first cross-linking agent, norbornadiene (CL-1), to both endo-DCPD and ENB resulted in decreasing glass transition temperatures with increasing concentrations. In contrast, the addition of the other two cross-linking agents (CL-2 and CL-3), which were both custom synthesized bifunctional norbornyl systems, to both endo-DCPD and ENB resulted in a monotonic increases in T _g with cross-linker concentration. By tailoring the loading of these custom cross-linking agents, the properties of these polymer systems can be controlled for various applications, including self-healing composites.     

A biospecific polymeric carrier for polypeptide drugs

Polymeric systems for targeting polypeptide medicinal drugs onto the wall of the small intestine after oral administration were synthesized. These systems are composed of particles of ovomucoid-modified polyacrylamide hydrogel with insulin physically immobilized in its bulk. In vitro experiments have demonstrated the enhanced stability of the immobilized polypeptide against proteolysis and the affinity of polymeric particles to lectin-containing surfaces. The efficiency of the systems obtained was demonstrated in experiments with animals and diabetes patients. The effrct of these systems upon oral administration was qualitatevely similar to that of subcutaneously administered native insulin.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2504–2509, November, 2004.     

Excess and partial excess molar volumes of mixing trimethyl- and triethylphosphate with water

Excess and excess partial molar volumes of mixing of the systems trimethylphosphate (TMP) and triethylphosphate (TEP) with water were determined at 15, 20, 25, 30 and 35°C. Negative deviation from ideal behavior were observed for the two systems studied, with a minimum at x _TMP =0.40 and x _TEP =0.35. Excess volume values in general decrease with temperature, and are smaller for the TMP-water system.     

A Calorimetric Study of Alloy Formation in Au-Cu and Au-In Systems

A calorimetric study of alloy formation in Au-Cu and Au-In systems was carried out. The heats of mixing, ΔH _mix, were measured at 1380,1484 and 1604 K for Au-Cu and at 1387, 1449 and 1505 K for Au-In in the full concentration range. The results of experiments were described by approximating equations. Observed values of ΔH _mix were discussed using the phase diagrams of the systems. It was shown that the systems become closer to the ideal state with increasing temperature. From the experimental data, the dependencies of the enthalpies of the systems on the composition and temperature were estimated. The simultaneous effects of composition and temperature on enthalpy are represented in 3D diagrams. The specific heats of the alloys, in the temperature range of experiments, were derived from the slopes of enthalpy planes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Liquid-Liquid Equilibria for Water + Nitromethane + (1-Propanol,or + Acetone,or + p-Dioxane) Ternary Systems at 303.15 K

Abstract

Liquid-liquid equilibria, distribution coefficients, and selectivities of ternary systems of the type: (water + K + nitromethane), where Kis 1-propanol, acetone, or p-dioxane, have been determined at (303.15 ± 0.05) K, in order to evaluate the suitability of nitromethane for extracting preferentially the second components from their aqueous solutions. The line data were satisfactorily correlated by the Othmer and obias method, and the plait point coordinates for the three systems were estimated. The experimental data were compared with values calculated using the NRTL and UNIQUAC models, and with those predicted by the UNIFAC group contribution method. This last method predicts qualitative and quantitative behaviour which are in disagreement with experimental results, while the values calculated using the other two models are in agreement but only when the concentration of component K is low. The three ternary systems studied have distribution coefficients higher than unity, and high selectivities. Therefore, nitromethane could be considered as a potential solvent for the extraction of K from its aqueous solutions     

Trapping efficiencies of various collection solvents after supercritical fluid extraction

A polarity test mix consisting of acetophenone, N, N-dimethylaniline, naphthalene, decanoic acid, 2-naphthol, and n-tetracosane was spiked onto sand, and extracted with supercritical carbon dioxide, to evaluate the collection efficiency of various solvents and solvent mixtures. Nine single collection solvent systems and four mixed collection solvent systems were studied. When one-component collection solvents were employed, quantitative (above 90%) recovery of all analytes was not possible. With mixed collection solvents, recoveries of 90% or better with all analytes studied were possible.     

Physical properties of the ternary system (ethanol + water + 1-butyl-3-methylimidazolium methylsulphate) and its binary mixtures at several temperatures

In this paper, we report experimental densities, dynamic viscosities, and refractive indices and their derived properties of the ternary system (1-butyl-3-methylimidazolium methylsulphate + ethanol + water) at T = 298.15 K and of its binary systems 1-butyl-3-methylimidazolium methylsulphate with ethanol and with water at several temperatures T = (298.15, 313.15, 328.15) K. These physical properties have been measured over the whole composition range and at 0.1 MPa. Excess molar volumes, viscosity deviations, and excess free energy of activation for the binary systems at the abovementioned temperatures, were calculated and fitted to the Redlich–Kister equation to determine the fitting parameters and the root-mean-square deviations and for the ternary systems were calculated and fitted to Cibulka, Singh et al., and Nagata and Sakura equations. The ternary excess properties were predicted from binary contributions using geometrical solution models. Refractive indices were measured from T = 298.15 K over the whole composition range for the binary and ternary systems. The results were used to calculate deviations in the refractive index.     

Precision synthesis of microstructures in star‐shaped copolymers of ϵ‐caprolactone,L‐lactide,and 1,5‐dioxepan‐2‐one

Star‐shaped homo‐ and copolymers were synthesized in a controlled fashion using two different initiating systems. Homopolymers of ε‐caprolactone, L ‐lactide, and 1,5‐dioxepan‐2‐one were firstly polymerized using (I) a spirocyclic tin initiator and (II) stannous octoate (cocatalyst) together with pentaerythritol ethoxylate 15/4 EO/OH (coinitiator), to give polymers with identical core moieties. Our gained understanding of the versatile and controllable initiator systems kinetics, the transesterification reactions occurring, and the role which the reaction conditions play on the material outcome, made it possible to tailor the copolymer microstructure. Two strategies were used to successfully synthesize copolymers of different microstructures with the two initiator systems, i.e., a more multiblock‐ or a block‐structure. The correct choice of the monomer addition order enabled two distinct blocks to be created for the copolymers of poly(DXO‐co‐LLA) and poly(CL‐co‐LLA). In the case of poly(CL‐co‐DXO), multiblock copolymers were created using both systems whereas longer blocks were created with the spirocyclic tin initiator. © 2008 Wiley Periodicals, Inc. JPolym Sci Part A: Polym Chem 46: 1249–1264, 2008     

Thermosetting epoxidized polybutadiene/low-molecular weight polyphenylene oxide compatible system with quite low-dielectric constant and loss prepared through co-curing reaction

Through the redistribution reaction of PPO, the hydroxyl-terminated low molecular weight PPO (PPO-OH) was prepared. Furthermore, after the reacting of PPO-OH with methacrylic anhydride, the double-bond-terminated low-molecular weight PPO (R-PPO) were synthesized, its M_n was 2631 g/mol. The R-PPO were co-cured with epoxidized polybutadiene (JP-100) to prepare JP-100/R-PPO cured systems. The JP-100/R-PPO cured systems showed single-phase morphology. The co-curing reaction with R-PPO could effectively improve the thermal performance of JP-100, the glass transition temperature (T_g) of cured JP-100/R-PPO systems raised greatly. For the cured JP-100/R-PPO (100/30) system, its T_g was 192°C. The dielectric constant and dissipation factor of cured JP-100/R-PPO systems were both decreased and showed good frequency stability. The dielectric constant and dissipation factor at 1 MHz of cured JP-100/R-PPO (100/30) system were 2.61 and 0.0038, respectively, were obviously lower than those of cured JP-100 system (which were 3.10 and 0.0099, respectively). The JP-100/R-PPO systems exhibited an excellent thermal stability. The 5% weight loss temperature (T_5%) of cured JP-100/R-PPO system was around 340°C.     

Iron‐Catalysed Radical Polymerisation by Living Bacteria

The ability to harness cellular redox processes for abiotic synthesis might allow the preparation of engineered hybrid living systems. Towards this goal we describe a new bacteria‐mediated iron‐catalysed reversible deactivation radical polymerisation (RDRP), with a range of metal‐chelating agents and monomers that can be used under ambient conditions with a bacterial redox initiation step to generate polymers. Cupriavidus metallidurans, Escherichia coli, and Clostridium sporogenes species were chosen for their redox enzyme systems and evaluated for their ability to induce polymer formation. Parameters including cell and catalyst concentration, initiator species, and monomer type were investigated. Water‐soluble synthetic polymers were produced in the presence of the bacteria with full preservation of cell viability. This method provides a means by which bacterial redox systems can be exploited to generate “unnatural” polymers in the presence of “host” cells, thus setting up the possibility of making natural–synthetic hybrid structures and conjugates.     

Iron-Catalysed Radical Polymerisation by Living Bacteria

The ability to harness cellular redox processes for abiotic synthesis might allow the preparation of engineered hybrid living systems. Towards this goal we describe a new bacteria-mediated iron-catalysed reversible deactivation radical polymerisation (RDRP), with a range of metal-chelating agents and monomers that can be used under ambient conditions with a bacterial redox initiation step to generate polymers. Cupriavidus metallidurans, Escherichia coli, and Clostridium sporogenes species were chosen for their redox enzyme systems and evaluated for their ability to induce polymer formation. Parameters including cell and catalyst concentration, initiator species, and monomer type were investigated. Water-soluble synthetic polymers were produced in the presence of the bacteria with full preservation of cell viability. This method provides a means by which bacterial redox systems can be exploited to generate “unnatural” polymers in the presence of “host” cells, thus setting up the possibility of making natural–synthetic hybrid structures and conjugates.     

Metal-containing initiator systems. VI. Polymerization of butadiene with metal–organic halide systems

The polymerization of butadiene with binary initiator systems consisting of some activated metals and organic halides was investigated at 60°C. From the results obtained, it was found that systems of reduced nickel and methyltrichlorosilane or dimethyldichlorosilane were most effective for the polymerization, and those of reduced nickel and carbon tetrachloride, benzyl chloride, benzyl bromide and benzoyl chloride, showed moderate activity. The polybutadienes obtained with these systems were observed to contain product of more than 80% cis-1,4 microstructure. From detailed studies on the reduced nickel–methyltrichlorosilane system, these polymerization mechanisms were explained by the hypothesis that the initiation occurred through the reaction of the dissociated transition state complex with the monomer or with a trace amount of water, and then the propagation proceeded via a coordinated cationic mechanism. These systems did not show a good activity for the cis-1,4 polymerization of isoprene.     

Different catalytic systems on hydroxyl-terminated GAP and PET with poly-isocyanate: Curing kinetics study using dynamic in situ IR spectroscopy

Reactions of hydroxyl-terminated glycidyl azide polymer (GAP) or poly(ethylene oxide-co-tetrahydrofuran) (PET) polymers with poly-isocyanate (N100) were monitored by dynamic in situ Fourier transform infrared spectroscopy. The influence of catalytic systems on the cure kinetics of polyurethane reaction was investigated. From the comparison between GAP/N100 and PET/N100 systems, it was found that primary and secondary hydroxyl groups were differentiated due to the effects of steric hindrance. Using Arrhenius law and Eyring equation, the activation parameters of polyurethane reaction were calculated at different catalytic systems. The negative value of the activation entropy demonstrated an associative mechanism within the transition state.     

Electrical conductivity in solid solutions and in two-phase regions of the silver halide-bivalent metal (cadmium,cobalt, zinc) halide systems

Electrical conductivity of solid systems AgX-MX₂ (where M=Cd, Co, Zn and X=Cl, Br) were measured in a large range of temperature and compositions. Activation energies and conductivity values vs. composition are presented and discussed in relation to phase equilibria in the respective systems. Maximum of the conductivity value and stabilization of the activation energy have been found for silver halides doped heavily with divalent cation e.g. in the systems forming solid solutions on the silver halide side. Disorder in AgBr on the approach to melting, expected to be higher than in AgCl, has been shown by means of original DSC curves presented for both halides.