Viscoelastic response of elastomers in large deformations

A simple nonlinear theory of viscoelasticity has been developed for application to elastomers. The interpretation of nonlinear viscoelastic responses based on Gibbs-DiMarzio theory has been identified at a molecular level and hence structural understanding has been established. The introduced model is applied to strain imposed conditions. From this, a relaxation process has been revealed for the resultant stress, where a dependence of relaxation time on the state of strain has been established.     

Preparation and polymerization of a diisocyanate from the Diels-Alder adduct of levopimaric acid and acrylic acid

Starting from tetrahydroabietic acid the model compounds tetrahydroabietoyl chloride, 2-aminoethyltetrahydroabietate hydrochloride, and 2-isocyanatoethyltetrahydroabietate have been prepared. Carbamate and urea derivatives of the isocyanate have been prepared. A Diels-Alder adduct of levopimaric acid and acrylic acid has been prepared and converted to its diacid chloride. The β-aminoethyl ester hydrochloride has been synthesized and converted to a diisocyanate which has been polymerized with poly(tetramethylene glycol) and also with p-phenylenediamine. Dimerex resin, a technical polymerized rosin, has been similarly converted to a diisocyanate. This isocyanate has not proven to be useful as a polymer-forming intermediate.     

A fluorimetric and circular dichroism study of hemoglobin--effect of pH and anionic amphiphiles

In this work, bovine hemoglobin (Hb) has been studied mainly by the fluorescence method. pH has been found to exert a profound effect on Hb structure. This has been confirmed by fluorescence and circular dichroism (CD) studies. The pH-induced change in quaternary structure of Hb indirectly affects its secondary structure. This in turn affects ligand binding to Hb at various pH. The binding of two amphiphiles, a bile salt and a surfactant, have been investigated. The pH-induced structural modification of Hb has been confirmed by studies with the well-known denaturant urea and the polarity probe ANS, which has been used as an extrinsic fluorophore.     

Kinetics and mechanism of the production of higher olefins from stearic acid in the presence of an alumina-supported nickel sulfide catalyst

A nickel sulfide catalyst which efficient in the decarbonylation of fatty acids to olefins and dienes has been obtained for the first time by treating alumina-supported nickel sulfate with hydrogen, and its properties have been studied. In its presence, the olefin selectivity of the reaction can exceed 90%. The kinetics of stearic acid deoxygenation to heptadecenes has been investigated, a kinetic model has been constructed, and a mechanism has been proposed for the reaction over this catalyst. Olefin oligomerization is the dominant side reaction. Kinetic evidence for the catalytic inhibition of oligomerization by nickel hydrides formed on the catalyst has been obtained. The compositions of active site–reactant adsorption complexes have been discussed.     

Kinetics and mechanism of oxidation of cyclopentanone by N-bromosuccinimide

N-bromosuccinimide oxidation of cyclopentanone in acidic media in presence of mercuric acetate has been made. A zero order dependance to N-bromosuccinimide and a first order dependence to cyclopentanone and hydrogen ion concentration has been observed. Ionic strength, mercuric acetate and succinimide has negligible effect while methanol addition has a positive effect. Various rate parameters have been computed and 1,2-cyclopentanedione identified as the end product. A suitable mechanism in confirmity with the above observations has been proposed.With 2 Figures     

A study of the effect of network angle of fabrics on kinetics of impregnation upon molding of articles made from carbon plastics

The permittivity coefficient, volume, and porosity of an elementary cell of fabric filler have been calculated. Two types of fabric structures have been considered using the example of carbon fabric: standard, in which filament yarn is cylindrical, and spread, it which it has a rectangular shape. A reflector of a mirror space antenna has been considered characterized by the presence of doubly curved surfaces is used as the object of study. Modeling of the kinetics of impregnation of reflector for two types of fabric structures has been carried out using the RAM–RTM program. In the work, the effect of the network angle on the duration of impregnation process has also been investigated. Based on the results of calculation, reflector samples have been made and their quality has been evaluated. Theoretical and experimental results have been compared.     

Ionization probability of the hydrogen atom suddenly released from confinement

The problem of the stability of a confined atom when it is extracted from the confining cavity has been investigated, modeled by a spherical hard wall potential. The ionization probability when the atom is released from confinement has been obtained. The dependence of the ionization probability on the confinement radius and on the quantum numbers of the initial confined state has been studied. The probability density function of the ionization energy of the ejected electron has been obtained for the different cases considered. The oscillatory structure of this distribution function, with a principal maximum located in the neighborhood of the energy of the initial state and minima very close to zero has been elucidated. The sudden approximation has been applied and the analytic continuation method has been used to calculate the different stationary states.     

Electrophoretic Mobility of a Polyelectrolyte Capsule

The electrophoretic motion of a polyelectrolyte capsule has been considered in a uniform electric field. The capsule carries a uniformly distributed charge and is permeable to ions of different natures. An electrolyte identical to a dispersion medium is located inside the capsule. The flow in the porous layer of the capsule has been described by the Brinkman equations taking into account the effect of electrostatic forces. The distribution of ions in the vicinity of the capsule has been determined, and its electrophoretic mobility has been found in a linear approximation. The mobility of the capsule has been studied as depending on its geometric characteristics, permeability, and charge density. In particular, a complex extremal character of variations in the mobility as depending on the solid phase fraction in the capsule has been revealed at different ratios between the thicknesses of the electrical double layer and the Brinkman filtration layer.     

Alpha-cyclodextrin functionalized CdS nanocrystals for fabrication of 2/3 D assemblies

Different types of cyclodextrins (CDs) have been tested as mediators for the water phase transfer of organic-capped CdS nanocrystals (NCs), and alphaCD has been demonstrated to be the most effective system. The formation of a complex based on alphaCDs and colloidal NCs has been considered to be responsible for the phase transfer process and extensively investigated by optical, structural, and calorimetric measurements, as a function of the experimental parameters (pH and NC and CD concentration). A mechanism for the complexation phenomena has been suggested. The fabrication of 2/3 D supramolecular architectures has been proposed according to two different strategies. First, a layer-by-layer procedure has been used to obtain multilayered structures where polyelectrolyte layers have been intercalated with negatively charged alphaCD-CdS NC complexes by exploiting electrostatic interaction between polyelectrolyte and cyclodextrin OH groups. Second, a monolayer of CdS NCs has been deposited onto a self-assembled monolayer of sulfated CDs, thus combining the use of an electrostatic-force-based approach and host-guest chemistry. The important role played by host-guest interactions has then been revealed.     

Synthesis and alkylation of 2-mercapto-4-quinazolone and the fungicidal activities of the compounds obtained

A convenient method of obtaining 2-mercapto-4-quinazolone has been developed and the alkylation of its ambidentate anions has been studied. It has been found that they exhibit a dual reactivity in alkylation reactions. It has been shown that alkylated 2-mercapto-4-quinazolones possess a moderate fungicidal activity.     

MNDO study of reaction paths: Hydroboration of methyl cyanide

The hydroboration reaction of methyl cyanide has been investigated by the MNDO method. It has been shown that the reaction requires an activation energy of 25.3 kcal/mol and involves a four-center-like transition state in the rate-determining step. This reaction has been compared with the corresponding reaction of hydrogen cyanide, and the effect of methyl substitution on the reaction has been discussed. The charge-transfer effects accompanying the reaction have also been studied.     

Synergism in the extraction of scandium

Synergism in the extraction of scandium by a mixture of di-2-ethylhexyl phosphoric acid and a β-diketone has been studied. The nature of the extracted species has been investigated. The effect of temperature on extraction has been studied and synergism has been explained on the basis of thermodynamic parameters of the extraction process.     

Deformation of gradient shape as a result of preferential adsorption of solvents in mixed mobile phases

Gradient elution has been studied in typical normal and reversed-phase systems. Deformations of gradient profiles have been evidenced as a result of preferential adsorption of modifiers of the mobile phase. This phenomenon was pronounced in the normal-phase system, for which gradient profiles deviated significantly from those programmed. This influenced the retention and shapes of band profiles of the eluting solute. Hence, in order to predict gradient propagation correctly the adsorption equilibrium of modifiers has been quantified. Moreover, at low modifier content, deformations of band profiles of the solute has been registered as a result of the competitive adsorption in the system solute-modifier. This effect has been predicted by a competitive adsorption model. For the reversed-phase systems the influence of the modifier adsorption on gradient propagation was insignificant for typical mobile phases investigated. Therefore, the work has been focused on gradient predictions in the normal-phase system.     

A three-component one-pot synthesis of penta-substituted pyrroles via ring opening of α-nitroepoxides

A novel and facile one-pot reaction has been developed to synthesize a variety of penta-substituted pyrroles from α-nitroepoxides, primary amines and dialkyl acetylenedicarboxylates under the conditions without catalyst. Furthermore, the controlled experiments has been performed and a possible mechanism has also been proposed.     

Thermodynamics of mixing of polymers

A method of calculating free energy of mixing of two polymers has been proposed. From a study of the sorption of organic solvents vapour by different polymers and their mixtures, Gibbs free energy of mixing for polymer-solvent systems are calculated. The free energy of mixing of two polymers has been calculated by the method proposed. Heats of mixing of polymers have been measured with a Calvet type microcalorimeter. Entropy of mixing has been calculated. Stabilities of polymer-polymer systems have been discussed.     

A study of the dioxane lignin of the stems of the cotton plant of variety S-4880

The dioxane lignin (DLA) has been isolated from the ripe stems of a cotton plant of the variety S-4880 B by a modification of Pepper's method. The yield was 16.9% on the Komarov lignin. The semiempirical formula of a phenylpropane structural unit has been calculated on the basis of elementary and functional analyses. It has been established that the amount of the main functional groups in the DLA and in the lignins isolated from the varieties of 108-F and Tashkent-2 basically coincide, but the DLA investigated was appreciably more highly methoxylated. The IR, UV, and PMR spectra of the DLA have been taken. The molecular-weight distribution of the DLA has been investigated and it has been shown that is is poly-disperse and has a weight-average molecular weight of 7400. Nitrobenzene oxidation and cleavage with sodium and liquid ammonia of the isolated DLA has shown that guaiacyl structural units predominate in it.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 430–434, May–June, 1987.     

Improvement of properties of silica‐filled styrene‐butadiene rubber composites through plasma surface modification of silica

The performance of plasma surface modified silica filler in styrene‐butadiene rubber (SBR) matrix has been analyzed. The conditions of plasma modification have been optimized by taking secant modulus as a standard parameter and the occurrence of the modification has been confirmed by surface area determination and Fourier transform infrared spectroscopy. The plasma‐modified surface of silica has been found to be composed of carbon–carbon double bonds and carbon–hydrogen bonds. Silane treatment also has been carried out on silica filler surface for a comparative assessment of its influence in the curing behavior and filler–rubber interaction. The cure reactions of all the rubber compounds have been found to be proceeded according to first‐order kinetics. A reduction in the cure reaction rate constant has been observed with the loading of unmodified and surface modified silica, emphasizing the cure deactivation of the matrix rubber by the silica filler. The filler dispersion, as revealed by scanning electron microscopy, has been found to be greatly improved by the plasma as well as silane treatment. The filler–rubber interaction has been found to be greatly improved by both surface treatments, but the best balance of mechanical properties has been observed with plasma surface modification only. Copyright © 2004 John Wiley & Sons, Ltd.     

The question of the production of Plantaglyutsid

The stage of extracting Plantaglyutsid from the leaves of rippleseed platain has been optimized by the methods of mathematical statistics. Information has been obtained on the optimum parameters of performing the process, as a result of which the yield of desired product has been increased and the amount of energy used and the consumption of extractant have been decreased.     

Modification of Chemically Amplified Resists by Radical Copolymerization

Modification of a phenolic resist has been carried out by copolymerization with methacrylic monomers. Influence of irradiation source and its intensity has been studied by analyzing sensitive curves of a various resist composition. Inversion of imaging type at varying post exposure bake temperature has been investigated for resists based on copolymers containing methacrylic acid units, which has been related with crosslinking of macromolecules.     

The Application of Modulated Temperature Power Compensation DSC to the Characterisation of Polymer Blends

A modulated temperature power compensated differential scanning calorimeter, MTDSC, has been built from a standard Perkin-Elmer DSC model-2 such that a computer generated voltage has been applied to induce a sinusoidal change in sample temperature superimposed on a linear heating rate. The effect of amplitude of the temperature fluctuation, modulation period and block temperature on the reversibility has been assessed from the Lissajous diagram of heat flow vs. sample temperature. From their reproducibility and symmetry the most effective conditions for operating the MTDSC has been deduced. The specific heat of sapphire has been measured using these operational conditions for comparison with conventional DSC. Phase separated blends of polycarbonate (PC) and polyethylene terephthalate (PET) have been analysed. This revised version was published online in August 2006 with corrections to the Cover Date.