bluuebunny/crossref_metadata_2025 huggingface dataset:
Purification of the precursor of bacterial cellulose
Authors: Colvin J. Ross , Leppard Gary G.
Published: June 2010

The precursor(s) of bacterial cellulose can be separated from cultures of Acetobacter xylinum by elution chromatography of lyophilized cells using chloroform, acetone, and 20% methanol in acetone. The last fraction, which contains the compound, may be purified by precipitation of glucose by diethyl ether and phase partition into petroleum ether, both at low temperature. Ability of the purified fraction to form cellulose microfibrils was demonstrated by electron microscopy. The active compound in the fraction was tentatively identified by thin layer chromatography, is very labile and has the properties of a lipid or lipid‐like substance.
The use of adsorbed cellulase in the continuous conversion of cellulose to glucose
Authors: Mandels Mary , Kostick John , Parizek Richard
Published: June 2010

Cellulose strongly adsorbs cellulase at pH 4.0‐5.0, 25‐50°C, conditions which are optimum for the enzyme action. The adsorbed enzyme is sufficient to digest the cellulose with no replenishment of enzyme even though the liquid phase containing the sugar is continuously removed. As cellulose is digested, the released enzyme is readsorbed on excess or newly added cellulose with retention of activity. Sugars can be separated from the enzyme‐cellulose complex by simple filtration or centrifugation or by retaining the enzyme‐cellulose complex in a column from which the sugar solution is eluted. Adsorbed cellulase has been used to produce syrups containing 5‐14% glucose continuously from stirred reactors containing 10‐20% cellulose, or from cellulose columns.
Structure of slippery Elm Mucilage(Ulmus Fulva)
Authors: Beveridge R. J. , Jones J. K. N. , Lowe R. W. , Szarek W. A.
Published: June 2010

The structure of the mucilage has been investigated using (a) the methylation procedure, (b) by oxidation of the polysaccharide with periodate (the Smith procedure), and (c) by its partial hydrolysis or methanolysis with the formation of sugars and oligosaccharides. It is composed of a main chain of alternating D‐galacturonic acid and L‐rhamnopyranose residues joined by a‐linkages through positions 4 of the galacturonic acid and 2 of the L‐rhamnopyranose. The polysaccharide has side chains, containing one or two residues of 3‐O‐methyl‐D‐galactopyranose or D‐galactopyranose, attached to some L‐rhamnose residues at C‐4 and C‐3, respectively. The synthesis of the disaccharide present at a branching point, namely, O‐(3‐O‐methyl‐β‐D‐galactopyranosyl)‐(1→4)‐L‐rhamnose is described.
The role of additives in the radiation induced copolymerization of monomers to cellulose
Authors: Dilli S. , Garnett J. L. , Martin E. C. , Phuoc D. H.
Published: June 2010

The radiation induced grafting of monomers to cellulose using a variety of solvents by the mutual irradiation technique is discussed. The monomers studied were styrene, 15 substituted styrenes, methylmethacrylate, vinyl acetate, and the vinylpyridines. The types of substituents examined included o‐, m‐, and p‐halogen derivatives, also the alkylstyrenes and certain methoxy monomers. The effect of wetting and nonwetting solvents in the grafting reaction was also investigated. A Trommsdorff effect (accelerated grafting) has been observed in certain systems at low doses and dose rates. The effect of oxygen, nitrogen, and vacuum on the Trommsdorff peak is discussed. The role of additives in the grafting of styrene is considered. The additives examined include aromatic and nonaromatic compounds, also typical free radical scavengers such as hydroquinone and thiourea. With certain additives sensitization is observed. A model for the grafting mechanism is proposed involving charge transfer bonded species. The role of energy transfer and free radical processes in the copolymerization reaction is also discussed.
Contributions to the grafting of the cellulose by radical mechanism
Authors: Simionescu Christofor I. , Feldman Dorel , Ciubotariu Martha
Published: June 2010

The grafting of the cellulose with vinyl monomers in the absence of the radical initiators was studied. The nature of the grafting medium and of the promoters was varied. The obtained copolymers have been investigated by chemical and physical‐chemical methods. The mechanism of the grafting was discussed.
Inorganic redox systems in graft polymerization onto cellulosic materials
Authors: Bains Malkiat S.
Published: June 2010

A review is attempted of the inorganic redox systems in the context of free radical graft polymerization. Metal ion‐H2O2 redox systems are considered as part of the spectrum of such inorganic and organic reagents used for the purpose. It is emphasized that the chemistry of these latter systems in particular is much like the radiation chemistry of aqueous solutions caused by high energy ionizing radiations. On the other hand, these systems involve low energy and therefore are less damaging to the substrate and relatively more specific. The reactivity of free radicals in these systems varies subtly with the system and the medium. It is observed that only ceric ion method and [Fe(II); Fe(III)] ‐H2O2 system are most successful in grafting onto cellulosic materials. Attention is paid to the features which makes these systems so useful. Concrete results from ESR study are presented which underline the nonspecific nature of various free radical producing systems including radiations.
Researches in the field of the grafting on cellulose with acrylic and methacrylic derivatives
Authors: Simionescu Christofor I. , Oprea Spiridon
Published: June 2010

The grafting on rayon fiber of acrylic and methacrylic monomers was studied through the decomposition of the hydroperoxide and peroxide groups, created in a process of ozonization. The graft copolymers was characterized by chemical analysis, infrared spectroscopy, and thermo‐oxidative decomposition.
Chemical structure of cellulose‐styrene graft copolymers
Authors: Sakurada I. , Ikada Y. , Nishizaki Y.
Published: June 2010

At first polyvinyl alcohol was used as a model for cellulose, and the grafting of styrene and methyl methacrylate was carried out in a heterogeneous system by use of mutual irradiation, preirradiation, and catalytic method. In all cases trichloroethylene or carbon tetrachloride was added to the reaction mixture to shorten the branches. True graft copolymers were isolated by vigorous alternate extraction of unreacted PVAL and homo‐PST (or‐PMMA), and hydroxyl groups in the copolymers were completely acetylated to carry out osmotic measurements. Molecular weights of the separated chains and the mother polymers were also determined by osmometry. It was shown that the graft copolymer has only one mother PVAL molecule and one graft branch regardless of the grafting methods employed. In the case of cellulose, high tenacity rayon was used as a substrate. The reaction product was acetylated, and the extraction of homo‐PST and unreacted cellulose (in the form of triacetate) was carried out with benzene (at 80°C) and CH2 Cl2 ‐MeOH (1:1, at room temp.), respectively. In this case also, it was shown that the graft copolymer molecule consisted of one graft branch and one mother cellulose molecule.
Phase separation in polymer solutions. I. Liquid‐liquid phase separation of PPO poly (2, 6‐dimethyl 1, 4‐phenylene oxide) in binary mixtures with toluene and ternary mixtures with toluene and ethyl alcohol
Authors: Van Emmerik P. T. , Smolders C. A.
Published: June 2010

In the system poly(2, 6‐dimethy1‐1, 4‐phenylene oxide) (PPO)‐toluene three phase separation lines can be detected: the melting point curve, the cloud point curve, and the spinodial. Because crystallization of PPO occurs very slowly, a phase transition will always be initiated by liquid‐liquid phase separation. Depending upon the experimental circumstances two mechanisms are possible, either nucleation and growth (extremely slowly in this system) or the spinodial decomposition mechanism. In the system PPO‐toluene‐ethanol, liquid‐liquid phase separation occurs leading to two bulk liquid fractions. Only in mixtures containing very small concentrations of alcohol can three phase separation curves be detected from which the position of the cloud point curve of the system PPO‐toluene can be confirmed.
Morphology of glassy polymers
Authors: Ali M. S. , Sheldon R. P.
Published: June 2010

A study has been made of the annealing process which takes place when glassy polymers are heated at temperatures near their glass transition temperatures. Low‐angle x‐ray diffraction measurements, extending previous work using wide‐angle techniques, infrared, laser‐Raman, and scanning electron microscopical studies reflect no difference between quenched and annealed polymer. Replica electron micrographs do however indicate some structural reorganization. Differential scanning calorimetry and stress‐strain studies in conjunction with density measurements show that changes in all these occur on annealing but that at the present time conclusive evidence of local chain parallization is still awaited.
Creep behavior of polycaproamide fibers in various stages of homogeneous cold drawing
Authors: Kudrna M. , Janáček J.
Published: June 2010

Creep of partly oriented polycaproamide fibers in the course of large tensile strain was investigated and the two‐parameter Voigt model was used to describe the resulting creep curves. It follows from the dependence of the constants of the Voigt model on the magnitude of deformation before the onset of the actual creep, that the decisive deformation mechanism consists in the destruction of microscopic regions, accompanied in a later stage by formation of microcracks. No major effect of temperature, within the range from 30 to 60°C, could be observed. The results are compared with the literature data on the nonhomogeneous deformation of less oriented polyamide systems in the same temperature region which exhibit different behavior.
Time‐temperature superposition in ultimate behavior of heterogeneous gels with varying microstructure
Authors: Raab M. , Pelzbauer Z. , Janáček J. , Štol M.
Published: June 2010

If water is present in a volume concentration higher than about 0.5 during the crosslinking copolymerization of poly(2‐hydroxyethyl methacrylate), porous heterogeneous systems are formed. Samples of poly(2‐hydroxyethyl methacrylate) obtained by polymerization in the presence of various concentrations of water and, therefore, exhibiting different heterogeneity, were swollen in water to equilibrium and used to investigate the ultimate behavior. Heterogeneity was characterized by the volume fraction of swollen polymer in the heterogeneous system and morphology was determined by electron and light microscopy. For all samples, the dependence of time to break on tensile stress, and tensile strength and strain at break at various temperatures have been measured. While the rupture stress of homogeneous samples is very temperature sensitive, the effect of temperature is much less pronounced in the case of highly porous samples. This phenomenon has been ascribed to the temperature‐independent coulomb friction which participates in the rupture process of heterogeneous gels.
Precision differential calorimetry and the heat of fusion of polyethylene
Authors: Richardson M. J.
Published: June 2010

A procedure is described for the analysis by computer of the output from a differential scanning calorimeter. Enthalpy calibration with a variety of materials confirms that alumina is excellent for this purpose.

Both the crystallinity, xT, and the heat of fusion of polyethylene, ΔHT, vary with temperature and it is important that both are measured. The use of a room‐temperature crystallinity with a high‐temperature heat of fusion can be very misleading. Interfacial effects are shown to be negligible in most cases and the heat of fusion of perfectly crystalline polyethylene is given by ΔHT/xT. It is 309 Jg−1 at the melting point.
Morphology of single‐textured polyethylene a new model for polymer in the oriented state
Authors: Point J. J. , Gilliot M. , Dosiere M. , Goffin A.
Published: June 2010

Small‐angle and x‐ray scattering (SAXS) and calorimetric studies support a model, previously proposed, which describes the structure of single‐textured polyethylene samples. These samples consist of distinct parts: some are made of lamellae and the others are without regular structure of the order of a few hundred angstroms. The reversibility and the kinetic of the evolution of SAXS patterns are due to the melting and the recrystallization of a part of the sample. Thermograms of samples annealed at high temperature show two melting peaks. The peak at the lower temperature is due to the melting of the lamellar crystals possessing a large thickness distribution which can be inodified by subsequent annealing. Melting and recrystallization of these lamellae affect the intensity of SAXS patterns. Thermograms of samples annealed at a relativity low temperature (To) present a third melting peak in the neighborhood of To. The thickness of the corresponding lamellae can be calculated from SAXS patterns. Thus lamellae are only a small fraction of the sample, not the whole as it was previously suppossed. The other fraction has no regular structure of the order of 100 Å.
Effect of jet stretching and draw ratio on the supermolecular structure of nylon 6 threads
Authors: Baranov V. G. , Bychkovsky N. I. , Goikhman A. Sh. , Nosov M. P.
Published: June 2010

The peculiarities of the spherulite structure formed in the course of nylon 6 fiber formation have been investigated. The dimensions and shape of the spherulites were determined by small‐angle scattering of polarized light with a simultaneous check by microscopy. Subsequent deformation at room temperature of the threads containing spherulites embedded in the amorphous glass‐like matrix causes the development and relaxation of stresses in the matrix. At this stage of elongation the spherulites themselves are “flattened” owing to the destruction of regions coinciding with the drawing direction. When the elongation exceeds X2.0 spherulite deformation sets in; it ends with the transition spherulite macrofibril. In the cross sections of the deformed samples spherulite‐like scattering and extinction patterns are observed up to sample rupture. This confirms that there is a direct genetic connection between the spherulite and orientational supermolecular order and indicates that the polarizability ellipsoids in the macrofibril exhibit complex distribution.
Electron‐microscopic study of polymer mixtures
Authors: Kazhdan M. V. , Bakeyev N. F. , Berestneva Z. Ya.
Published: June 2010

The effects of several factors on the morphology of films cast from binary polymer mixtures dissolved in a single solvent have been studied by electron microscopy. An elastomer‐elastomer system (isoprene rubber and polyisobutene) was used.

The effects of the relative amounts of components, change of the molecular weight of one of the components, the history of the solution, and the rate of evaporation of solvent on the morphology of films prepared from polymer mixtures were studied. It is inferred from the results that these factors affect the kinetics of the phase separation of polymer mixtures.
The effect of small quantities of structural plasticizer additive on the structure and properties of vulcanizates
Authors: Zharikova Z. F. , Reztsova E. V. , Berestneva Z. Ya. , Kargin V. A.
Published: June 2010

The effect of small quantities of an insoluble plasticizing additive (0.01‐5% by weight) on the structure and properties of vulcanizates of different rubbers has been studied. Silicone oil was used as the plasticizer. It has been shown that significant changes in the mechanical properties of vulcanizates are caused by this type of plasticizer. For instance, a polychloroprene vulcanizate specimen without plasticizer broke down after 25,000 cycles (in extension cycling tests) whereas the same specimen with 0.1% silicone did not break down after 360,000 cycles. It has been shown, with the use of electromicroscopic, IR spectroscopic and x‐ray diffraction methods, that the introduction of small quantities of plasticizing additive leads to the formation of more highly ordered supermolecular structures in vulcanizates. A mechanism proposed for the action of small quantities of additives on the mechanical properties of vulcanizates is based on the idea of structural plasticization.
Effect of high‐pressure annealing on the structure of oriented polyethylene
Authors: Zubov Yu. A. , Selikhova V. I. , Konstantinopolskaya M. B. , Sukhov F. F. , Slovokhotova N. A. , Bakeyev N. F. , Kruykov A. V. , Sokolsky V. A. , Belov G. P.
Published: June 2010

The effect of annealing at different temperatures and pressures of 3000, 5000, and 7000 kg/cm2 on the structure of oriented films of linear polyethylene has been studied. It has been established that for each of the above pressures there is an optimal temperature of annealing at which the maximum crystallinity of the sample is achieved. The results obtained by wide and small angle x‐ray diffraction, infrared spectroscopy, electron microscopy, and density show that annealing at the optimal temperature leads to extended‐chain crystallites in the sample. Orientation of crystallites remains largely unchanged.
Unperturbed dimensions and viscosity of polyarylates
Authors: Pavlova S. A. , Timofeeva G. I. , Menshov V. M.
Published: June 2010

Condensation polymers of phenolphthalein with sebacic acid (PA‐1) and of phenolphthalein with isophthalic acid (PA‐2) covering a wide molecular weight range were prepared and fractionated. Studies of solution viscosity were carried out on the fractions dissolved in tetrahydrofuran and in tetrachloroethane. Mark‐Houwink plots for PA‐1 are markedly nonlinear, and the effect is interpreted in terms of coil permeability. It is concluded that permeability effects are negligible in PA‐2. The molecular weight dependence of the second virial coefficient (determined by the Archibald method) in tetrahydrofuran is abnormal for both polymers. The characteristic unperturbed dimension for PA‐1 calculated by the Flory‐Williams method agrees with deductions from experiment.
Light scattering investigations on moderately concentrated solutions
Authors: Dautzenberg H.
Published: June 2010

We performed light scattering measurements on some polymers (polystyrene, polystyrene/poly(methyl methacrylate) graft copolymer, cellulose derivatives) to contribute to the clarification of the structure of solutions in the region of moderate concentrations. In particular, we investigated the influence of molecular weight, chain structure, and conditions of preparation of the solutions. Since a theory is lacking for the quantitative evaluation of scattering curves in this concentration range, we treated the results by the theories of dilute solutions and tried to draw conclusions about the structure of solutions at higher concentrations. Our results suggest network formation at high concentrations.
On the incompatibility of blocks in an isolated molecule of an A‐B block polymer. II. Application of the perturbation theory and of the Casassa‐Markovitz approximation
Authors: Pouchlý J. , Živný A. , Sikora A.
Published: June 2010

By use of the perturbation theory, the number of contacts between blocks in a molecule of an A–B block polymer is expressed as a function of an excluded volume parameter in the from of a power series. The first two coefficients of this series are evaluated as functions of the relative length of one of the blocks. Introducing an approximate assumption according to Casassa and Markovitz, a closed‐form expression is obtained; its limiting value and first derivative as the excluded volume effect vanishes are in agreement with those given by the exact power series. Similarly to the preceding results obtained with the Flory‐Krigbaum segment cloud model, it turns out that on a change of thermodynamic conditions the number of interblock contacts is lowered only gradually; however the extent of this block segregation is higher than that according to the Flory‐Krigbaum model.
Coil dimensions and hydrodynamic properties of methylmethacrylate random copolymers
Authors: Wunderlich W.
Published: June 2010

Light scattering and viscosity measurements have been carried out on random copolymers of methylmethacrylate with methyl, ethyl, and n‐butylacrylate as well as n‐butylmethacrylate in acetone at 20°C. The parent homopolymers have also been included in the measurements. Unperturbed dimensions and excluded volume parameters were evaluated from the experimental data. It has been found that the Flory's hydrodynamic constant Φo in copolymer systems exceeds the value calculated and experimentally determined for binary homopolymer solutions. Also, in a fairly good solvent, the copolymer coil behaves as if it were less expanded than it is in reality. The short range interactions exceed the mean value calculated from homopolymers in combining an α‐substituted monomer with an unsubstituted one. Long range interactions resulting from heterocontacts can be determined quantitatively and related to the incompatibility of the parent homopolymers.
Temperature dependence of the optical activity of nicotine salts of poly(methacrylic acid) in dilute aqueous solutions
Authors: Mihailov M. , Baldzhieva R.
Published: June 2010

The influence of temperature on the optical activity of dilute aqueous solutions of nicotine salts of poly(methacrylic acid) as well as of nicotine and the nicotine salt of pivalic acid has been studied. It was found that the temperature dependence of the optical activity is nonlinear, and reflects changes in structure and proteolytic equilibria in solutions. The variation of the temperature coefficient of optical activity of the solutions and its dependence on concentration and wavelength are discussed.
Light scattering of concentrated polydisperse polymer solutions
Authors: Scholte Th. G.
Published: June 2010

On the basis of the Smoluchowski‐Einstein‐Zernike theory, it is shown that light‐scattering measurements on mixtures can, in general, yield information about the second derivatives of the free enthalpy (Gibbs free energy) of mixing with respect to the concentrations. This method can be applied to concentrated solutions of polydisperse polymers or polymer mixtures. Integration of the appropriate experimental data yields the chemical potentials and the interaction parameters. From the same theory it follows that plotting of the reciprocal of the scattered‐light intensity versus the temperature for a number of compositions, and extrapolation to zero yields the spinodal. This procedure does not initiate from any particular molecular model. It can be applied to simple polymer solutions, but equally well to more complicated systems such as two polymers in one solvent or a mixture of two or more polymers. Spinodals have been determined for solutions in cyclohexane of three polystyrene samples with the same weight‐average molecular weight but differing in their width of distribution.
Phase separation in polymer solutions. II. Determination of thermodynamic parameters of poly (2,6‐dimethyl‐1,4‐phenylene oxide) toluene mixtures
Authors: van Emmerik P. T. , Smolders C. A.
Published: June 2010

In liquid systems where it is possible to perform light scattering experiments at the melting points of polymer solutions without nucleation taking place because of undercooling, the thermodynamic parameters necessary to calculate the correction parameter g in the Flory‐Huggins equation as modified by Koningsveld can be determined. In the system poly(2,6‐dimethyl 1,4‐phenylene oxide)‐toluene crystallization will be induced by liquid‐liquid phase separation at temperatures below the melting points. The Huggins interaction parameter x, calculated from light scattering data, shows negative values for solutions up to 24.5 weight per cent of polymer. This indicates specific interactions between polymer and solvent molecules. A combination of data from light scattering and from calculations based on the theory of melting point depression affords the values necessary for calculating the free enthalpy of mixing ΔG.
Antioxidants and stabilizers. XL. Contributors to the thermal decomposition of tert‐butyl hydroxyperoxide
Authors: Zikmund L. , Janota J. , Brodilová J. , Pospíšil J.
Published: June 2010

The rate of decomposition of tert‐butyl hydroperoxide in benzene solution within the temperature range of 132 to 170°C has been investigated. At concentrations of tert‐butyl hydroperoxide lower than 0.03 mole/1. the reaction occurs via a monomolecular mechanism (activation energy Eb = 36.7 ± 3 kcal/mole). At higher concentrations the initial rate of decomposition is that of a second‐order reaction with respect to hydroperoxide (activation energy Ea = 16 ± 4 kcal/mole). The reaction mechanism has been discussed, and the activation energy of the reaction of tert‐butoxyl radicals with tert‐butyl hydroperoxide has been estimated.
Antioxidants and stabilizers. XLI. reaction of tert‐butyl hydroperoxide with 2,2′‐methylenebis(4‐methyl‐6‐tert‐butylphenol)
Authors: Zikmund L. , Brodilová J. , Janota J. , Pospíšil J.
Published: June 2010

The reaction of tert‐butyl hydroperoxide with 2,2′‐methylenebis(4‐methyl‐6‐tert‐butylphenol) in a benzene solution was studied within the temperature range 132 to 170°C. The change in the concentration of both components and the formation of the products were investigated depending on time. The products thus formed were isobutylene, tert‐butyl alcohol, acetone, and the oxidation products of methylenebisphenol. Individual amounts produced depended on the reaction temperature and the initial concentration of the starting compounds. GPC was used for the following transformations of methyl‐enebisphenol. The decomposition of tert‐butyl hydroperoxide was found to be accelerated by the presence of methylenebisphenol, which, however, affects but little the splitting of the tert‐butoxyl radicals yielding acetone.
Antioxidants and stabilizers.XLII. Reaction of tert‐butyl hydroperoxide with mononuclear and binuclear phenols
Authors: Zikmund L. , Brodilová J. , Pospíšil J.
Published: June 2010

The effect of the structure of alkylphenols and methylene‐bisphenol on the course of decomposition of tert‐butyl hydro‐peroxide has been investigated. All phenols under investigation have been found to accelerate the decomposition to a varying degree. During the reaction, the phenols undergo oxidative transformation, resulting in the formation of oligomers as a methyl or ethyl group is substituted for phenols at the position para to the hydroxyl group. All types of phenols yield decomposition products which have a lower molecular weight than the initial phenol and are strongly absorbant in the UV region. Time dependences of the formation of tert‐butyl alcohol, isobutylene, and acetone have been tabulated. From the data measured, stoichiometric ratios q of the reaction of tert‐butyl peroxide with phenols and costants, expressing the rate of the loss of tert‐butyl hydroperoxide, have been calculated.
Transport of dissolved carbon dioxide through silicone rubber membranes
Authors: Hwang Sun‐Tak , Strong Gary D.
Published: June 2010

The transport of dissolved carbon dioxide through silicone rubber was studied as a function of concentration levels and membrane thicknesses. Investigations were made under steady‐state conditions only. A necessary provision to the determinations of permeability coefficients was the development of measuring the concentration of dissolved carbon dioxide in water. A method called “gas phase analysis” was developed. This procedure involves analysis of gas phase samples above CO2‐H2O solutions sealed in equilibrium vessels. The permeability was found to be very nearly independent of concentration level. The previously developed equation relating the reciprocals of permeability and membrane thickness was used to explain the experimental data. The importance of boundary resistance was emphasized.
Permeation of liquid water in a filled epoxy resin
Authors: Manson J. A. , Chiu E. H.
Published: June 2010

Certain epoxy paints and filled resins were shown to be potentially useful protective coatings for concrete exposed to hot saline media. Since, however, very little information was available about water‐polymer interactions at elevated temperatures, a study of permeation and of dielectric and mechanical relaxation was begun. In this part of the study, the permeation of liquid water through an epoxy film (filled with 0, 10, and 20 wt.‐% spherical glass beads) was measured at temperatures up to 130°CC. As expected, the filler served to decrease permeation, though to a greater extent than predicted. Arrhenius plots of permeation revealed several other characteristics. In general a discontinuity was observed at Tg, with the apparent energies of activation, Ea, being lower below Tg (4–11 kcal/mole, compared to 19–26 kcal/mole). Both the sharpness of the transition and Ea were sensitive to the history of the specimen. At elevated temperatures, the most highly filled specimen showed an additional relative decrease of permeability in comparison with other specimens. An interpretation of the data is proposed, based on segmental mobility as affected by restrictions due to the presence of filler particles.
A diffusion‐solubility model for reverse osmosis
Authors: Machacek Raymond F. , Osburn James O.
Published: June 2010

The sorption of a dye by hollow fiber nylon reverse osmosis membranes was measured. Equations for the unsteady state reverse osmosis separation of the dye from water are solved by numerical analysis, and are shown to fit data on this process. This gives credence to the assumed model, which is that of solution of dye in the membrane followed by diffusion through it.
Radical initiated synthesis of hydroxyl terminated polymers using aqueous hydrogen peroxide as initiator
Authors: Pinazzi Christian , Legeay Gilbert , Brosse Jean‐Claude
Published: June 2010

Aqueous hydrogen peroxide thermally decomposes into two hydroxyl radicals which readily initiate a radical polymerization process. Ethylenic monomers and aqueous hydrogen peroxide are generally nonmiscible liquids in all proportions, and the addition of an alcohol to the reaction medium greatly modifies the thermodynamic conditions. Liquid and solid products are obtained having 1.7 to 1.9 hydroxyl groups per macromolecule and their average molecular weights vary between 700 to 100,000. For diene monomer polymerization, low molecular weight oligomers as well as higher molecular weight polymers are obtained. Structures of the diene polymers obtained show that aqueous hydrogen peroxide‐initiated polymerization proceeds by a 1, 2 addition for their initiation step and a 1, 4 addition for propagation.
A model for the solid state polymerization of calcium acrylate hydrates
Authors: Watine F. B. , St‐Pierre L. E.
Published: June 2010

The variations in the rates of polymerization of calcium acrylate hydrates as a function of composition, in vacuo and in air, are described by a three‐phase model in which only two phases undergo polymerization at any given composition. It is proposed that an “active” phase which involves the total monomer volume is present at the 0.5 H2O hydrate. This active volume concept supersedes the phase boundary model previously employed to explain the nonlinear polymerization‐composition behavior.
Contribution of water to the initiation of solid state polymerization of acrylate and methacrylate salt hydrates
Authors: Watine F. B. , St‐Pierre L. E.
Published: June 2010

The role of the water of crystallization in the initiation of the solid‐state polymerization of calcium acrylate and barium methacrylate hydrates has been investigated in terms of its physical and chemical involvement in the polymerization reaction. The dynamics of the water of crystallization was studied by infrared absorption on D2O hydrated salts in the presence of water vapor. The variation of the relative intensities of the OD and OH bands in the infrared spectra showed that a rapid exchange occurred between the water of crystallization and water in the atmosphere. ESR studies on D2O hydrated salts proved that radicals, produced from the water, contribute substantially to the initiation of the polymerization reaction.
On the mechanism of radiation‐induced crosslinking of poly(vinyl chloride) in the presence of some polyfunctional monomers
Authors: Sukhov F. F. , Slovokhotova N. A.
Published: June 2010

Some features of low‐temperature radiolysis of poly (vinyl chloride) and the effect of added polyfunctional monomers such as triallyl cyanurate have been studied using the technique of infrared spectrophotometry. It has been found that the radiation yield of HCl formed in the radiolysis of poly(vinyl chloride) alone at 100°K is equal to 2.5. Additives form a complex with radiolytically produced HCl. The structure of this complex corresponds to on oxonium compound. The radiation yield of the complex reaches 50–80 per 100 eV of energy absorbed by additives. At the same time, the addition of triallyl cyanurate in poly (vinyl chloride) decreases the radiation yield of HCl associated with polymeric matrix by 2–3 times. The reaction of the allyl groups of the additive with the polymer free radicals already occurs at low temperatures. On heating, the irraditated at low temperature samples, the complex of additive with HCl decomposes, the remaining allyl groups disappear, and triazine rings are partly transformed to the isocyanurate form. These results are interpreted in terms of a mechanism which postulates the localization of the dehydrochlorination process of poly(vinyl chloride) in the vicinity of the additive molecules and the promotion of crosslinking efficiency by the formation of complex of additive with HCl.
Light activated polymerization of isobutylene by friedel‐crafts catalysts
Authors: Marek M. , Toman L.
Published: June 2010

The effect of light upon the course of the polymerization of isobutylene catalyzed with the Friedel‐Crafts halides and carried out at temperatures ranging from 0 to –78°C in the solution of n‐heptane was investigated. The polymerizations carried out under dry conditions in the dark at temperatures lower than –40°C in the presence of VCI4, TiCl4, TiBr4, and TiI4 as catalysts practically did not occur at all. If, however, the reaction mixture was irradiated with visible, ultraviolet, or infrared light, rapid polymerization occurred, which stopped when the light source was switched off and which was accelerated again when the light was switched on. In the case of polymerizations activated with visible light, the polymerization and conversion rates depend upon the kind and concentration of the catalyst used and on the temperature and intensity of the light source. The polymerization rate decreased in the order VCI4 > TiCl4 > TiBr4 > TiI4; in all cases it increased with decreasing temperature. No accelerating effect of the light used could be observed for polymerizations catalyzed with the AlBr3 and SnCl4 halides. The possible radical‐cationic polymerization mechanism is discussed.
Quantum theoretical calculations concerning the copolymerization behavior of vinyl monomers and restricted rotation in radicals of vinyl polymerization
Authors: Roth H.‐K. , Fleischer G.
Published: June 2010

Some features of the addition reaction of vinyl polymerization were investigated. The factors influencing the copolymerization behavior of the monomers was found by MO calculations. The meaning of Q of the Q‐e scheme of Alfrey and Price shows the resonance stabilizations could be confirmed. The meaning of e was found in the electrostatic interaction between monomer and radical in the transition state caused by the dipole moments of monomer and radical. The radical motions, especially the rotation around the last C‐C bond, are treated. A quantum mechanical formalism describing this rotation is declared.
Effects of association of unsaturated polyesters on their reactivity in copoly‐merization with monomers
Authors: Bulatov M. A. , Spasskii S. S. , Surovtsev L. G.
Published: June 2010

The high reactivity of fumaric polyesters in copolymerization reactions with monomers are discussed. The monomers acting as poor solvents cause association of the polyester. Double bonds in the associate may be ordered in such a way that the resulting arrangement favors the homopolymerization reaction. Effects of these structures may display in polymerization of low molecular compounds such as benzyl methacrylate. The relation between the polymerization rate of the associated monomer and the association degree is determined.
Study of the polymerization of acrylonitrile in dimethylformamide solution in the presence of tetramethyl thiuramdisulfide
Authors: Beniska J. , Štaudner E.
Published: June 2010

The induced polymerization of acrylonitrile (AN) in dimenthylformamide solution in the presence of various concentrations of tetramethylthiuramdisulfide (TMTD) at temperatures of 55, 58, 60, and 63°C, was studied. It was found, that TMTD has an inhibiting effect on the polymerization. It was also shown that the products formed during the inhibition period have a retarding influence on the further course of the polymerization. The equations for the polymerization rate during and after the inhibition period were derived. The inhibition and retardation effects of TMTD on the polymerization of AN in solution can be expressed by the help of the complex constant B+ and of the empirical constant b, respectively.
Photocopolymerization of acrylonitrile with methacrylic esters in the presence of anthraquinone dyes
Authors: Nuta Violeta , Feldman D. , Simionescu Cr. I.
Published: June 2010

Photocopolymerization of acrylonitrile (AN) with methacrylic esters such as methyl methacrylate (MMA), butyl methacrylate (BMA), and lauryl methacrylate (LMA) using as photosensitizer the anthraquinone dye, Indanthrone Yellow 3R (1Y‐3R), was studied. The best conversions depending upon the ratio between monomers and the duration of the process was followed and the reactivities of the comonomers (the reactivity ratios and Q and e parameters) were determined. One did find a reactivity modification in proportion as the methacrylic ester chain increased.
Polymerization of vinyl chloride by organolithium compounds. II. Polymerization of vinyl chloride by organolithium complexes
Authors: Jíšová V. , Kolínský M. , Lím D.
Published: June 2010

The study of the polymerization of vinyl chloride by organolithium compounds was further extended to also cover polymerizations by complex catalysts containing alkyllithium together with dicyclopentadienyl titanium dichloride (Cp2TiCl2). Attention was paid to the effects of (a) the concentration of the complex and (b) the ratio at which the fundamental components were employed in the complex on conversion and molecular weight of the resulting product of polymerization.
The copolymerization of propylene and vinyl chloride with the Ziegler‐Natta catalysts: Infrared spectra and the structure of copolymers
Authors: Kissin Yu. V. , Dankovics A.
Published: June 2010

This work is devoted to the infrared study of the products of the copolymerization of propylene and vinyl chloride with the modified TiCl3–Et3Al catalyst.

Thus, in our view the data given demonstrates two important features of the copolymerization process of propylene and vinyl chloride on the modified Ziegler‐Natta catalyst: 1. that real copolymerization takes place in the case of this monomer pair; and 2. that copolymerization procedes on the stereospecific active sites of the heterogeneous catalyst, i.e., on the same sites which are responsible for the stereoregular polymerization of olefines. Infrared study allows one to estimate the distribution of the propylene units in the copolymers. The distribution is very typical of the random copolymers obtained with the stereospecific catalysts.
Two types of recrystallization processes during annealing of stretched linear polyethylene
Authors: Hosemann R. , Loboda‐Čačković J. , Čačković H.
Published: June 2010

Linear polyethylene (PE), warmed up to 80°C only in the shoulder of necking process, can be stretched about 10‐fold. This material was annealed at a temperature T1 for t1 minutes and investigated by a two dimensional analysis of X‐ray small‐ and wide‐angle scattering at room temperature. By annealing at T1 ≥ 110°C after some minutes, a special recrystallization takes place for a short time, where the macroscopic density γ is constant and adjacent paracrystalline domains recrystallize to larger paracrystalline domains while the g13‐tensor component of the superlattice discontinously obtains a sharper component. This indicates that in connection with the above mentioned lateral recrystallization, the folding surfaces of the adjacent domains align to stepless larger surface areas. During this process the back folding of the chains firstly becomes quite irregular. After and before this special process, where in the γ − 1/P diagram a horizontal plateau exists, γ monotonically encreases with 1/P (P = long period) Here the averaged thickness of the paracrystalline smectic‐like layers slowly increases. This can be explained partially by lateral disintegration of paracrystalline layers, which do not go through the whole bulk material. The incubation time for the begining and end of the plateau decreases with increasing T1 > 110°C. This can be explained by raising the mobility of kinks within the paracrystalline domains with raising T1. The single ultrafibrils during annealing have not lost their character consisting of pearl‐string‐like chains of paracrystallites connected to each other by tie molecules. They have only aligned to their neighbors with a higher order: they develop well defined larger inner folding surfaces and paracrystalline domains extending over several ultrafibrils.
Isothermal crystallization studies on nylon 6.6 and 6.10 by calorimetry
Authors: Savolainen A.
Published: June 2010

The DSC technique was used to investigate the isothermal crystallization of nylon 6.6 and nylon 6.10. It is shown that the Avrami equation in the case of the crystalline polymers is useful during the hole crystallization process. The observed differences in the activation energies of crystallization of annealed and untreated nylon 6.6 and 6.10 polymers are due to the differences in inner order in the specimen during the primary and the secondary crystallization.
Solution properties of cyclo‐ and cyclized polyisoprenes
Authors: Vohlídal J. , Boháčková V. , Matyska B.
Published: June 2010

A series of linear 1, 2 and 3, 4 polyisoprenes were cyclized to various degrees by the action of TiCl4 and POCl3 as catalysts. Light scattering and viscometric studies of cyclized samples showed that the cyclization process was accompanied by an increase of the steric hindrance factor σ up to a certain value. At higher degrees of cyclization, on the other hand, the characteristic dimensions of the macromolecules diminished due to the internal cross‐linking.
Structural levels of supermolecular organization in aqueous solutions of poly (vinyl alcohol)
Authors: Klenin V. J. , Klenina O. V. , Kolnibolotchuk N. K. , Frenkel S. Ya.
Published: June 2010

The isothermal rise in supermolecular order (SMO) in aqueous solutions of poly (vinyl alcohol) (PVA) over a wide range of temperature and concentration and also under shear has been studied. SMO was characterized by the equivalent average radius of super‐molecular particles (SMP) rΛ, estimated by the turbidity spectrum τ = τ(Λ).

The methods of gradient dependence of viscosity electron and polarize‐optical microscopy, and light scattering according to Debye‐Zimm have also been used.

It is shown that the process of isothermal rising of SMP over a wide range of temperature and solution concentration consists of two distinct stages: a relatively rapid rise and then a slow rise of SMP.

In aqueous PVA solutions SMO represents, generally, the hierarchy of some its levels. The first level is considered to be the supermolecular particles, which form after the dissolution of the whole polymer mass. The character of this level is determined by the microstructure of the sample in the condensed state and dissolution conditions. The particles of the first level are the heterogeneous formation nuclei of the second level–particles of the fibril type. Fibrils, which have risen from the solution at high temperature (T ≥ 80°C) have shown the ability to aggregate into anisodiametric structures as the solution cools. These aggregates, determined to be the third level, are very sensitive to temperature. In turbulent shear the rising rate of SMO increases greatly as the characteristic concentration is made smaller.

The results obtained give us reason to conclude that the rise in SMO in aqueous PVA solutions is due to the crystallization of macromolecules when the low molecular weight component is available.
Polypeptide helix lifetimes in the helix–random coil transition region. Application to NMR spectra
Authors: Ferretti J. A. , Jernigan R. L. , Weiss G. H.
Published: June 2010

Two rate processes characterize the helix‐random coil transition in synthetic polypeptides. A slow rate is obtained by an interpretation of separate helix and random coil peaks in the NMR spectra. A faster rate is obtained from relaxation time measurements which utilize rapid reaction techniques. The present model describes the time dependent behavior of polypeptides in the transition region by combining random walk probabilities with conventional equilibrium distributions of conformations. Average conformational lifetimes for each peptide unit were calculated for molecules containing up to 150 units. These results indicate that in the transition region no helical unit is sufficiently long lived to be individually distinguishable by NMR. Spectra are simulated using a two site model for exchanging systems. On the basis of these model calculations the two peaks observed in the NMR spectra are attributed to (1) the all random coil species and (2) all other conformations containing at least one helix unit.
Dilute solution viscosity and conformation of poly‐n‐hexyl isocyanate
Authors: Berger M. N. , Tidswell B. M.
Published: June 2010

Poly‐n‐hexyl isocyanate, prepared according to the method of Shashoua, was fractionated by a coacervation technique. Light scattering and osmometric measurements show that the molecules are enormously extended in solution and can be described in terms of the Porod‐Kratky worm‐like model.

Dilute solution viscosity measurements were carried out in a series of solvents and solvent/nonsolvent theta mixtures. Mark‐Houwink constants are reported in which the exponent is very high (a > 1) for both pure solvents and theta mixtures. In nonpolar solvents the polymer molecules are too stiff to respond to long‐range thermodynamic forces. The chains relax somewhat in chloroform and on the addition of trifluoroacetic acid due to a change in the effect of short‐range forces. [η] decreases with increasing temperature indicating that the more compact conformations of the molecules have higher energy states than the more extended ones.
Copolymerization and structure of copolymers of α, β‐unsaturated aldehydes with styrene
Authors: Kálal J. , Houska M. , Seyček O. , Adámek P.
Published: June 2010

The radical bulk copolymerization of styrene with acrolein, methacrolein, and α‐ethyl‐acrolein is studied and monomer reactivity ratios are determined. Employing the dilatometric method the overall rate of polymerization is measured and discussed with respect to the special structure of copolymers. Quantitative IR spectroscopy is used to elucidate the structure of copolymers, and the absorption behavior of copolymers is compared with the statistical theory on sequence length distribution.