bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electron‐electron double resonance study of polymer chain motions
Authors: Yang Henry W. H. , Chien James C. W. 
Published: June 2010

AbstractThe technique of frequency‐swept electron–electron double resonance (ELDOR) has been used to study polymer chain motions in dilute solutions. ELDOR effects have been measured at different temperatures and pump powers. The maximum de‐enhancements obtained by extrapolating the data to infinite pump powers were used to interpret molecular motions. Amorphous polystyrene with nitroxides spin‐labeled at both chain ends was employed in this study. The result agrees excellently well with the result obtained from electron spin resonance (ESR) line‐width analysis. Both the activation energy (12 kJ/mole) and the correlation times of the motion, were found to be significantly smaller than the values obtained from other ESR and nuclear magnetic resonance (NMR) studies on aromatic substituted polystyrene. Explanations were given as due to the smaller steric hindrance and less backbone coupling among neighboring bonds for the local motions of polymer chain ends.
Dielectric relaxation behavior of some ethylene‐methacrylic acid copolymers and their methyl esters
Authors: Neumann R. M. , Macknight W. J. 
Published: June 2010

AbstractEthylene‐methacrylic acid copolymers containing two different concentrations of the acid groups have been studied by dielectric relaxation and infrared techniques. The infrared measurements, used to determine the number of acid dimers present at a given temperature, indicate a sufficient number of free COOH dipoles present to account for the magnitude of the observed β dielectric relaxation (frequency plane) in both copolymer systems. Dielectric measurements on the methyl ester derivatives of the abov́e copolymers yield dispersions of unusual width, which precluded attempts to estimate the number of ester dipoles participating in the relaxation. A possible explanation for this behavior is advanced.
Some rheological properties of polycarbonate blends
Authors: Dobrescu Viorica , Cobzaru Valentin 
Published: June 2010

AbstractThe influence of the nature and proportion of components in the blends of polycarbonate (PC) with poly(methyl methacrylate) (PMMA), ABS, polyethylene (PE), and polypropylene (PP) upon the rheological properties in the molten and solid state was studied. It has been observed that the PC‐PMMA system is compatible in the molten state, while the other systems are incompatible. For incompatible systems, as blending ratio increases, the melt viscosity of blends goes through a minimum. The experimental results support the idea of reciprocal lubricating effect of polymeric components.
Radical cyclo‐ and cyclocopolymerization
Authors: Butler George B. 
Published: June 2010

AbstractAlthough the principles of cyclopolymerization have been well established, certain aspects of the originally proposed mechanism still remain to be justified in terms of experimental observations. It is the purpose of this paper to discuss these conflicting aspects, to present new information, and to point out those areas where no single mechanistic explanation is presently sufficient. The areas to be considered are: (1) much evidence is available that the cyclization step proceeds via a fast concerted reaction, while kinetic studies on a limited number of monomers indicate that the activation energy for cyclization is greater than that for linear propagation; and (2) although six‐membered rings are predicted in radical cyclopolymerization of 1, 6‐dienes, based upon radical stabilities, numerous examples of such polymerizations are now known to lead to large fractions of five‐membered rings; in addition, extensive stuides on model compounds leading to small molecules have shown that the five‐membered ring is predominant. New evidence indicates that a driving force for cyclization may be that the cyclized polymer is in a lower free energy level than the monomer; also, that radical stability exerts a marked influence on the ring size. This paper also includes the results of a study designed to determine the effect of the nature of a substituent at the 5‐position of 5, 6‐unsaturated radicals on the ring size of the cyclic product. Thus, it was shown that 2‐methallyloxy ethyl radical yielded five‐ to six‐membered rings in the ratio of 30:1, while the 2‐(2‐phenylallyloxy)ethyl radical yielded products in the ratio of 1:2. The latter structure which simulates cyclopolymerization of di(2‐phenylallyl)ether reflects the stabilizing influence of the phenyl group on the intermediate radical. The rate constants and energies of activation for the competing reactions were determined.
Free radical and ionic grafting
Authors: Kennedy Joseph P. 
Published: June 2010

AbstractAdvantages and disadvantages of graft copolymer syntheses by free radical and ionic (i.e., anionic and cationic) techniques are compared. Recent significant advances in the field of cationic graft copolymerizations are summarized and discussed. Particular emphasis is placed on cationic syntheses which employ alkylaluminum coinitiators in conjunction with macromolecular initiators which produce unadulterated, pure graft copolymers, e.g., EPM‐g‐polystyrene, SBR‐g‐polyisobutylene, chlorobutyl‐g‐polystyrene. In these systems grafting efficiencies are close to 100%, which demonstrates by direct gravimetric analysis that chain transfer can be completely eliminated in carbenium ion polymerizations. The synthesis of PVC‐g‐polytetrahydrofuran which involves the grafting of THF from PVC using silver salts also leads to pure graft. Finally, cationic systems which either directly or after selective extraction produce pure grafts and thus allow the examination of physical properties of pure materials will be presented.
Grafting process in vinyl acetate polymerization in the presence of nonionic emulsifiers
Authors: Gavǎt I. , Dimonie Victoria , Donescu D. , Hagiopol C. , Munteanu Mariana , Goşa Kristiana , Deleanu Th. 
Published: June 2010

AbstractThe influence of vinyl acetate grafting reactions or nonionic type emulsifiers on the kinetics and on properties of emulsions has been studied. The emulsifiers used were polyvinyl alcohol and block copolymers ethylene oxide–propylene oxide. Due to the grafting reactions the polymerization rate decreased or increased with the increase in polyvinyl alcohol concentration, depending on the emulsifier/monomer ratio. During polymerization, graft copolymers of the monomer on the emulsifier chain are obtained. These copolymers are either water‐soluble, benzene‐soluble, or insoluble in water and benzene. The number of grafting reactions increases with the rise in initiator concentration. This leads to a decrease of benzene‐soluble fractions and to an increase of the water‐soluble and water‐and‐benzene‐insoluble fractions. The concentration of emulsifier in water‐and‐benzene‐soluble fractions was established by NMR analysis. The IR spectra of products proved the formation of graft copolymers.
Some relationships between physical properties and morphology of heterogeneous polymeric systems
Authors: Lindenmeyer P. H. 
Published: June 2010

AbstractThe effect of morphology on the physical properties of heterogeneous polymeric systems may be quantitatively expressed by a single parameter called the contiguity parameter. The formalism of small systems thermodynamics holds considerable promise of providing the means for a quantitative theoretical understanding of the very complicated morphological structures which exist in polymer solids.
Solute binding and catalysis by poly(vinylbenzo–18–crown–6)
Authors: Smid J. , Shah S. C. , Varma A. J. , Wong L. 
Published: June 2010

AbstractPoly(vinylbenzo–18–crown–6), abbreviated as P18C6, and a polymer endowed with the cation binding crown ether ligand benzo–18–crown–6 as pendent groups, exhibits in water strong hydrophobic interactions with organic solutes such as picrates and methylorange. The binding can be modified by addition of crown ether complexable cations which superimposes an electrostatic component on the hydrophobic interaction forces. Thermodynamic parameters for the picrate binding have been determined, ΔH being –11.9 kcal/moleand ΔS = –16.8 e.u. This type of binding was utilized to catalyze reactions which are known to be sensitive to the polarity of their micro environment. The P18C6 catalyzed decarboxylation of sodium–6–nitrobenzisoxazole–3–carboxylate in water was studied in detail, and the kinetics were found to resemble that of a micellar catalyzed reaction. The hydrophobic interaction of the carboxylate with P18C6 is weak, but the binding can be greatly enhanced by addition of KCl. The rate constant of decarboxylation of the substrate in the polymer domain was found to be between 2000 to 5000 times larger than that in water, depending on the charge density on the polymer. Finally, the interaction of P18C6 with polyanions such as sodium carboxymethylcellulose is discussed. Formation of insoluble polysalt complexes can be observed in the presence of KCl and CsCl.
Abiotic synthesis and the properties of some protobiocopolymers
Authors: Simionescu C. I. , Dénes F. , Negulescu I. 
Published: June 2010

AbstractThe appearance and the properties of protobiocopolymers are critically discussed. Simulating the geologically relevant primeval Earth conditions, i.e., taking into account the early atmosphere, hydrosphere, and available energies, the possibility of simultaneous appearance of some protobiocopolymers is suggested. The self‐assembling of these macromolecules in well‐defined individual systems (microspheres), their special electrical properties, such as membrane potential and semiconductivity, and their stability in rather severe physicochemtcal conditions, e.g., pH, temperature, mechanical stress, and irradiation with UV light, bring forward the “protocell” which could arise on this track on our primitive planet.
Possibilities of obtaining polymers with supposed antitumor activity
Authors: Iliev I. B. , Georgieva M. P. , Kabaivanov V. S. , Popov D. V. 
Published: June 2010

AbstractIt is known that dichloroethylamines in which the two chloroethyl groups are bound to different N atoms at a given distance from each other retain their activity and considerably lower their toxicity. It was assumed that by controlling the distance between the two chloroethyl substituents to the polymer chain a product of analogous action could be obtained. Two possibilities of binding monochloroethylamine (MCA) to a polymer were investigated: (1) Copolymerization of N‐vinyl pyrrolidone (VP) with monochloroethylamide of methacrylic acid (MCAMA). The constants of copolymerization of this pair: r1 = 3.88 ± 0.31 and r2 = 0.089 ± 0.017 were determined, as well as the mean length of the elementary link of the copolymer chain. It was found that at a ratio of VP:MCAMA = 1:3 a copolymer of statistically probable structure could be obtained in which the distance between two monochloroethylamine groups is the most appropriate: about 6 atoms. (2) A polymer‐analogous reaction of the copolymer of VP with maleic anhydride (MA) permitting the binding of MCA to the polymer chain by severing the MA ring. It was established that the reaction proceeded best in a medium of dimethylformamide at 80°C for 1 hr. Water‐soluble products characterized by their C1 content and ir spectra were obtained. These products showed a physiological activity.
The effect of polyaspartamides on drug‐metabolizing enzymes
Authors: Drobník J. , Kálal J. , Dabrowska L. , Praus R. , Váchová M. , Elis J. 
Published: June 2010

AbstractRat liver β‐D‐glucuronidase was inhibited in vitro by a 1% concentration of dextran and polyvinylpyrrolidone at low enzyme concentrations. Pentosan polysulphate showed a similar effect, while three derivatives of the polyaspartamide were inactive. Microsomal aniline hydroxylase was inhibited by a 0.75% concentration of all polymers tested, the most active being the lysine derivative of polyaspartamide. No effect on the cytochrome P‐450 ‐ carbon monoxide reaction was detected. Microsomal aminopyrine demethylase activity was only slightly depressed by polymers, except for pentosan polysulphate, which showed stimulation. The carboxyethyl derivative of polyaspartamide induced in vivo the activity of N‐acetyltransferase.
Sustained release hormonal preparations for the delivery of fertility‐regulating agents
Authors: Benagiano G. , Schmitt E. , Wise D. , Goodman M. 
Published: June 2010

AbstractDelivery systems represent the most important new approach to prolong the duration of action of contraceptive steroids. They utilize existing fertility‐regulating agents and enhance their duration of action by establishing a drug reservoir. These systems constitute an advancement in the effort to maximize subject compliance and minimize subject‐physician interactions. Three types of delivery systems are under development at present: nonbiodegradable devices made of polysilicone tubings filled with contraceptive progestins; biodegradable systems that need not be extracted from the body and can be prepared both as cylindrical rods to be inserted subcutaneously or as injectable micropellets; and programmed release devices where the active principle will be diffused only during specified times of the female cycle. Devices made of polysilicone have already been tested clinically, whereas biodegradable systems are at the preclinical testing level. Finally, programmed release devices are still at an early feasibility stage.
Bioactive polymers. III. Cellulose derivatives as support for biologically active compounds
Authors: Simionescu Cr. , Dumitriu S. , Bulacovschi V. , Popa V. I. 
Published: June 2010

AbstractSynthesis of bioactive cellulose derivatives was realized. The employed methods were the coupling of antibiotics and enzymes on various cellulose derivatives. The antibiotics were bound to cellulose carbonate and diazonium salts of cellulose aminoaromatic esters, giving compounds with good antimicrobian activity. In spite of the loss of mobility, attached enzymes still obey Michaelis‐Menten kinetics to a first approximation, i.e., yield linear Lineweaver‐Burk plots from which it is readily possible to extract characteristic values of the parameters. The Michaelis‐Menten constant for immobilized amyloglucosidase on cellulose carbonate at pH 8 was 8.42 mM, and the activation energy for starch hydrolysis was 22,100 cal/mole.
On the medical use of cyanoacrylic esters: Toxicity of pure n‐butyl‐α‐cyanoacrylate
Authors: Mungiu C. , Gogălniceanu D. , Leibovici M. , Negulescu I. 
Published: June 2010

AbstractIn vivo action of poly(n ‐butyl‐α‐cyanoacrylate) has been investigated on white rats and mice, taking into account their weight evolution, sanguine distribution, tissular hepatic and renal respiration, and anatomico‐pathological examination of different organs. An insignificant toxicity has been observed in each case and the results show conclusively that the use of n ‐butyl‐α‐cyanoacrylate monomer can be extended to human surgery.
Protein and lipid adsorption by acrylic hydrogels and their relation to water wettability
Authors: Holly Frank J. 
Published: June 2010

AbstractRadiochemical techniques were applied to determine protein and lipid uptake by acrylic hydrogels. The water wettability of these gels was previously obtained by using contact angle goniometry and was found to depend mainly on the composition of the polymer matrix but not on the equilibrium water content. Three hydrogels, poly(hydroxyethyl acrylate), poly(glyceryl methacrylate), and poly(acrylamide), had approximately the same equilibrium water content, therefore the same approximate penetrability with respect to protein. The uptake of both the protein (bovine serum albumin) and the lipid (cholesteryl oleate) appeared to be directly related to the water–gel interfacial tension, whereas the ease of removal was inversely related to water wettability. A cationic preservative, benzalkonium chloride, increased the protein uptake somewhat for two of the hydrogels. Preexposure to proteinaceous solutions had a pronounced effect, increasing the lipid uptake by the hydrogels, with the exception of PGMA. The results obtained appear to support the minimum interfacial free‐energy hypothesis of biocompatibility.
Hydrophilic grafting on poly(vinlfluoride) films by means of accelerated electrons
Authors: Fuehrer J. , Ellinghorst G. 
Published: June 2010

AbstractThe surface grafting of hydrophilic monomers on poly(vinylfluoride) films by means of low‐ energy electrons is described. The preirradiation technique was used by irradiating dry films in vacuo. The graft monomers were vinylacetate, acrylic acid, hydroxyethylmethacrylate, N‐vinylpyrrolidone, acrylamide, 4‐vinylpyridine and vinylenecarbonate. The influence of radia‐ tion dose, radiation dose rate, grafting temperature, and irradiation temperature on the grafting yield was investigated. Besides the gravimetrical and spectroscopical determination of grafting some chemical reactions at the functional groups of the grafted monomers were performed.
Thermotropic liquid‐crystalline polymers: A new type of mesomorphic macromolecular system
Authors: Platé N. A. , Shibaev V. P. 
Published: June 2010

AbstractA new approach to the synthesis of thermotropic liquid‐crystalline (LC) polymers is described based on the polymerization of monomers containing various mesogenic groups attached to the backbone chain by flexible polymethylene spacer groups. Dozens of new LC polymers are described, including derivatives of polymethacryloyl L‐lysine, cholesteric esters of long‐chain aminocarboxylic acids, and other aromatic polymers. Phase transition temperatures, heats of fusion, and x‐ray structural analysis were evaluated. Polymers exhibiting spontaneous optical anisotropy in the glasslike, elastic, and fluid states are described, and schemes of molecular packing in the LC phase are proposed. We show the possibility of realizing smectic, nematic, and cholesteric types of structures in these thermotropic LC polymers. An LC structure for various comblike copolymers not having mesogenic groups at every monomeric unit was detected. The role of specific interactions in side groups and their mobility in allowing for the LC structure are discussed, and the necessity of having particular conformations of the macromolecules is shown to provide the LC structure in films made from various solutions.
Some new developments in the field of reactive polymers and immobilized enzymes
Authors: Manecke Georg , Vogt Hans‐Günter 
Published: June 2010

AbstractA review of reactive carriers and immobilized enzymes describing the latest developments in the authors' laboratories is presented. Slightly basic and amphoteric reactive carriers were synthesized on the basis of poly (ethylene imine), and neutral hydrophilic carriers were obtained on the basis of polyethers. A new possibility for the Ugi reaction including carbon dioxide as the fifth component in this reaction is shown. Crosslinked acrylic acid–styrene copolymers and also poly(vinyl alcohol) were used for the introduction of maleimide groups, giving polymers with a specific reactivity towards SH‐groups containing enzymes resp. thiolated enzymes. A poly(vinyl alcohol) containing fiber material, synthetic pulp, was modified with diazonium groups and used for the immobilization of different enzymes. The properties of the immobilized enzymes were investigated.
Enzymes immobilized by graft copolymerization to different polysaccharides
Authors: D'Angiuro L. , Focher B. , Cremonesi P. , Mazzola G. , Vecchio G. 
Published: June 2010

AbstractA method for grafting enzymes on polysaccharides using a redox system as a radical initiator is reported (Fe2+‐H2O2). Glycidylmethacrylate was used as a vinylating reagent and the reaction product with enzymes (HRP, GOD, Am, ChT) was copolymerized with different matrices (cellulose, Sepharose, Sephadex, starch). During the enzyme vinylation reaction, no appreciable denaturation was observed, and various products were obtained using chromatography. Various factors affect the final activity of the copolymers; these include the redox system, the type of support, and the quantity and type of vinyl monomer added. Using a fixed quantity of enzyme, recovery of activity varied 2–50%. Graft copolymers thus obtained appear to be stable in storage and present higher thermal stability than that of the free enzyme. The kinetics of these copolymers indicate that diffusion is not appreciably limited, and that the immobilization reaction does not alter the enzymatic activity.
Comments on the reproducibility of GPC measurements
Authors: Samay Géza , Füzes László 
Published: June 2010

AbstractThe short‐ and long‐time reproducibility of GPC performance was investigated for two GPC systems. In the case of the short‐time measurements the standard deviation of the peak elution volumes and the relative standard deviations of the Mn and Mw values were found to be independent of the molecular weight. Considerable differences were found in the position of the peak elution volumes of calibration standards in the case of the high‐temperature system during a 3‐yr period, whereas no significant deviations were detected in the case of the GPC system operated at ambient temperature within a 2‐yr interval. The separation efficiency of the columns was also investigated but no significant changes in the peak widths were observed either at high or at ambient temperature.
Application of average retention volumes in gel‐permeation chromatography calibration. Model calculations
Authors: Szewczyk Pawel 
Published: June 2010

AbstractTo determine the absolute calibration equation of a gel‐permeation chromatograph, unimodal standards of any polydispersity may be used; assuming a polynomial model of the calibration equation and using average retention volumes of corrected chromatograms of these standards in the calculations. Formula defining the individual average retention volumes are simple polynomial expressions. Differences in the polydispersity of standards contained in the interval 1.1–2.0 have no influence on the results of determination of the calibration. Application of average retention volumes in the calculations enables the acquisition of an absolute nonlinear calibration, even in cases when statistical criteria permit only linear relationships between log M and Vv which are the starting equations of further calculations; M and Vp are the average molecular weight and the peak retention volume, respectively.
Microscopic determination of the size of polymer microparticles and their changes in the presence of liquids
Authors: Viceník P. , Pecka K. 
Published: June 2010

AbstractApparatus for microscopic evaluation of gel microparticles (size 5–500 μm) is described. As many as a hundred particles fixed in twenty through‐flow cells can be examined in the presence of a flowing liquid. This arrangement makes possible static and dynamic measurements of particle size and shape, and their changes in contact with liquids. Examples of kinetic measurements of swelling and a study of the homogeneity of various xerogel particles are given.
Mixed‐polymeric stationary phases in gas chromatography
Authors: Klein J. , Widdecke H. , Wolter G. 
Published: June 2010

AbstractThe behavior of mixed‐stationary phases, prepared from polystyrene‐polybutadiene using different techniques (mixed‐bed columns, deposition of homopolymer mixtures, deposition of copolymers, deposition of homopolymers in controlled‐layer sequence) is compared for different solutes (solvents and nonsolvents) over a wide temperature range including the glass‐transition region of polystyrene.