bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase diagrams and pulse‐induced critical scattering
Authors: Gordon M. , Irvine P. , Kennedy J. W.
Published: June 2010

Recent theoretical progress and major advances in computational methodology for spinodal and critical points make Pulse‐Induced Critical Scattering (PICS) a fast and reliable tool for examining statistical mechanical hypotheses, as expressed in the free energy of mixing function for solutions of linear polymers, and for measurement of the moments Mr = Σiwimir of the molecular weight distribution. Theoretical interpretation of measured phase diagrams has been hampered by 1) a lack of sufficiently reliable information on Mr(r = 1, 2, 3) of samples available from standard sources, and 2) the mental effort required in deriving spinodal and critical point equations from the increasingly complex free energy of mixing functions via the determinants of Willard Gibbs. Three strategies help to counter these difficulties: 1) Two molecular weight distributions (MWDs) are called r‐equivalent if they share at least the first r moments; computer software is available to determine the mixture of [r/2] sharp fractions which is r‐equivalent to a given MWD; thus the mixing of a small number of components gives access to an unlimited range of mixed samples whose moments are known (in terms of those of the components) to an accuracy set only by the analytical balance. 2) A spinodal truncation theorem (and critical point conjecture) exploits the concept of r‐equivalence since they determine the set of moments on which spinodal and critical point loci depend in addition to those moments featuring in the free energy expression. 3) Application of powerful algorithms of the QR‐type to the eigenvalue problems posed by the Gibbs spinodal and critical conditions have removed the necessity for prior excursions into the algebra of determinants by the human experimenter, since now spinodal and critical points can be numerically computed easily and directly from any postulated free energy function, especially when we employ the truncation theory and the notion of r‐equivalence. In consequence, the rapid feedback now possible with computer explorations of theoretical hypotheses is helpful in advancing the thermodynamics of polymer solutions and exploiting more fully the tools, such as PICS, for monitoring the relevant effects experimentally.
Gas‐ and liquid‐like phase dualism in polymers
Authors: Baranov V. G. , Frenkel S.
Published: June 2010

An analysis of the behavior of polymer systems in the condensed amorphous state shows that they may resemble both gases (e.g., high elasticity) and liquids (high density, ability to flow and crystallize, etc.). Moreover, polymer systems, analogously to gases, exhibit distribution according to their thermodynamic potentials, which for polymers is connected with the distribution according to end‐to‐end distances, while for gases it is related to the distribution according to velocities (in both cases we have a Maxwell distribution). The similarity between gases and macromolecules is also suggested by the low proper density of the latter (∼0.05 for the θ‐dimensions).

The preceding facts allow us to formulate the concept of phase dualism, according to which each segment of the polymer system in the condensed state possesses at the same time features both gas‐like and liquid‐like. The occurrence of one or the other of the likenesses or their simultaneous occurrence depends on the direction and scale of the segment's reaction towards external effects (field of force, temperature, etc.). Keeping in mind the existence of phase dualism one may describe, at least in a thermodynamically formal way, virtually all the peculiar features of the behavior of polymer systems in various transitions.

In particular, a quantitative and qualitative interpretation is possible of a nontrivial transition from crystallization with chain folding to crystallization with chain extension for when a system containing randomly coiled macromolecules is compressed on all sides. In this case the compression will affect the dual phase system in two ways. First, the segment liquid will be compressed while the internal energy will be reduced by ΔUt and second, the interaction between the segments will be strengthened. The thermodynamic characteristics of the “segment gas” under compression on all sides must be altered, losing some gas‐like qualities, towards the transition of the whole system into a “real liquid.” Such a transition is feasible if the statistical coil forms a compact globule, or if it becomes straightened and forms nematic structures, while the internal energy changes by ΔUg. An analysis of the thermodynamic losses caused by such transitions shows that a transition of the latter type, i.e., with unfolding of the macromolecular chains, is the more likely one. Earlier investigations carried out by us indicate that on reaching some critical degree of unfolding, a transition must occur from crystallization with folding to crystallization with extension, which, together with the conclusion mentioned above, explains the specificity of crystallization under hydrostatic compression. Quantitative evaluations of pressure at which the transition from one manner of crystallization to another should occur give P > 2500 atm, in good accord with the experimental data.
Spectrometer for the investigation of small‐angle neutron scattering using the time‐of‐flight method
Authors: Gladkikh I. , Kunchenko A. B. , Ostanevich Yu. M. , Cser L.
Published: June 2010

Investigation of small‐angle neutron scattering by the time‐of‐flight method and the basic characteristics of the spectrometer used are briefly described. First experiments with protein solutions confirming the suitability of the method are reported.
Polymer/polymer diffusion. I. Experimental technique
Authors: Price Fraser P. , Gilmore Paul T. , Thomas Edwin L. , Laurence R. L.
Published: June 2010

Diffusional processes in polymer blends, although important in determining the characteristics of the blend, are poorly understood. Virtually no data are available in the open literature. A novel experimental technique useful in the study of diffusion in compatible polymer/polymer systems is presented. It uses a scanning electron microscope and dispersive energy analysis of the x‐ray fluorescence profile in the interdiffusion of two polymer components. The technique is used to determine the diffusivity in a poly(vinyl chloride)‐poly(±‐caprolactone) at 70°C. The diffusion coefficient [D = (1.59 ± .13) × 10−12cm2/sec] is of the same order as the only reported polymer/ polymer diffusion measurements.
Small‐angle X‐ray scattering from block polymer micelles
Authors: Legrand D. G.
Published: June 2010

It has been found that the AB block polymers of polystyrene and poly(dimethylsiloxane) form micelles in normal alkanes. The micelles are swollen by methylene chloride or cyclohexane which gives to an increased turbidity and an increased mobility of the polystyrene. Small–angle x–ray scattering data indicate that the polystyrene decreases in size as methylene chloride or cyclohexane are added. A model is proposed to explain these results.
Analysis of conformational contributions to polymer properties at the glass transition
Authors: O'Reilly James M.
Published: June 2010

The conformational contributions to the specific heat at constant volume by the chain backbone and side groups are reviewed. Calculations from rotational isomeric state models support the previous results for the backbone contribution for simple vinyl chains. Contributions from side chains are consistent with other experimental data. A rotational contribution in a liquid lattice is found in glass‐forming liquids. A conformational contribution to the relaxation of the adiabatic compressibility is discussed.
Electron‐electron double resonance study of polymer chain motions
Authors: Yang Henry W. H. , Chien James C. W.
Published: June 2010

The 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

Ethylene‐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

The 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

Although 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

Advantages 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

The 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

The 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

Poly(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

The 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

It 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

Rat 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

Delivery 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

Synthesis 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

In 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

Radiochemical 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

The 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

A 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

A 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

A 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

The 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

To 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

Apparatus 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

The 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.
Specific heat capacities of the ternary system water + rnase + KCL and of human erythrocytes. Some remarks to the mathematical description
Authors: Müller R. G. , Hasl G. , Pauly H.
Published: June 2010

For the ternary system water + RNase + KCl and equally for packed human erythrocytes the specific heat capacities were measured in the range from 282 to 353 K. It is shown that an expansion of cp according to the McMillan–Mayer theory is helpful to the interpretation of the experimental data of the ternary system. Moreover, it will be shown that a first mathematical approximation for cp of human erythrocytes leads to an astonishing conformity with the experiments.
Some structural and biochemical features of the products of enzymatic and alkali‐salt dissolution of mature fibrillar collagen
Authors: Babloyan O. O. , Borisova M. A. , Gorbatov V. M.
Published: June 2010

This article investigates the influence of enzymatic and alkali‐salt treatment of the fibrillar collagen on the structure of the final products of dissolution with the help of the methods of infrared (IR) spectroscopy and differential thermal analysis. In addition we compared the products obtained by the two methods of treatment using two biochemical indices: content of ester bonds and hydroxyproline. One can conclude that enzymatic treatment is optimum for dissolution of the fibrillar collagen.
Manifestation of intraglobular dynamics at microcalorimetry of leghemoglobin crystals
Authors: Makarov A. A. , Mgeladze G. N. , Monaselidze D. R. , Esipova N. G.
Published: June 2010

Differential scanning microcalorimetry and microscopy have been used to study thermal transitions in leghemoglobin crystals. It is observed that leghemoglobin crystals do not melt and that their lattices disappear because of denaturation of protein globules inside them. An increase in the cooperativity of a thermal transition and in the relaxation time of the system are peculiarities of the crystalline state. Consistent study and comparison of the two stages of heat absorption by leghemoglobin crystals have allowed us to estimate the physical process that takes place in them and to relate the heat absorption peaks to different intramolecular processes. The first peak reflects intramolecular motility of both single protein segments with respect to each other and single fragments of the α‐helical regions. Therefore, the method of differential scanning microcalorimetry may be seen as the most suitable for the analysis of features of intramolecular dynamics of globular proteins, which are in the crystalline state, since the crystal synchronizes the motility of single molecules due to a unification of their kinetic energy, environment, and coorientation.
New electrically conductive polymers. Dopant and architectural effects on the collective properties of cofacially joined metallophthalocyanines
Authors: Dirk Carl W. , Inabe Tamotsu , Lyding Joseph W. , Schoch Karl F. , Kannewurf Carl R. , Marks Tobin J.
Published: June 2010

An integrated chemical and physicochemical investigation of the cofacially joined metallomacrocyclic polymers [M(Pc)O]n (M = Si, Ge, Si) and the halogen‐doped, electrically conductive derivatives {[M(Pc)O]Xy}n (X = I; M = Si, Ge; X = Br; M = Si) is reported. The structures of these polymers have been studied by X‐ray diffraction, resonance Raman, transmission infrared, transmission optical, 13C CP‐MAS NMR, and EPR spectroscopy. The picture which emerges is that of inhomogeneously doped, mixed‐valent arrays of predominantly ligand‐oxidized (π radical cation) metallomacrocycles. Magnetic susceptibility and optical reflectivity measurements reveal a progressive increase in tight‐binding bandwidths with decreasing interplanar (ring‐ring) spacing. Studies of dc electrical conductivity as a function of dopant level and temperature suggest that transport in these heterogeneously doped materials can be satisfactorily described with percolation theory and fluctuation‐induced carrier tunneling. The conductivity is a sensitive function of the ring‐ring stacking separations; evidence is presented for “metal‐like” (dσ/dt < O) conductivity in the {[Si(Pc)O]I1.12}n stacking direction with σ ≈ 100 Ω−1 cm−1.
A viscosity study of mixtures of sodium smectite and poly(vinyl alcohol) in water as a function of pressure
Authors: Ali Sabz , McAtee James L. , Claesson Stig
Published: June 2010

Viscosities of mixtures of poly(vinyl alcohol) and Na smectite in water were measured at several pressures by using Couette and falling‐body‐type viscometers. The values of viscosity of clay‐polymer mixtures were found to bear an exponential relationship to the concentration of the polymer. The viscosities of these mixtures could be related to the concentration of clay by Arrhenius law at low concentrations or by Weltmann and Green's equation at high concentrations. The viscosities of polymer, clay, and clay–polymer mixtures increase exponentially with pressure.
The structure of crystals formed from dilute polymer solutions
Authors: Domszy R. C. , Glotin M. , Mandelkern L.
Published: June 2010

The structures of crystallites formed from a dilute solution of linear polyethylene and of an ethylene‐butene copolymer (hydrogenated polybutadiene) have been studied using several different methods. In addition to the conventional thermodynamic methods, small‐angle x‐ray scattering measurements and analysis of the low‐frequency Raman longitudinal acoustic mode (LAM) were also carried out. The major objectives were to establish the level of crystallinity and to determine the thickness of the crystallite core. The results of these studies were also applied to the analysis of the literature data for isotactic polystyrene crystallites formed from dilute solution. For the linear chains and the isothermally crystallized copolymer the different methods gave essentially the same results. The thickness of the amorphous overlayer for the lamellas formed by the homopolymers was found to be about 25 Å, in agreement with previous conclusions. It represents about 20–30% of the lamellar thickness. For the isothermally crystallized copolymers, the overlayer thickness increases to as much as 60 Å and the level of crystallinity is reduced to about 50%. For the rapidly crystallized, small crystallite size copolymer there is a discrepancy in the sizes obtained by the different methods. Possible reasons for the differences are pointed out However, a rather large overlayer is still deduced. When examined in perspective, it becomes clear that the lamellar‐like crystallites, typical of crystallization from dilute solution, contain a significant disordered overlayer. The relative extent of this overlayer depends on the chain structure.
Static and dynamic light‐scattering studies of poly(vinyl acetate) in the glass transition region
Authors: Tribone J. , Jamieson A. M. , Simha R.
Published: June 2010

An optically clear sample of undiluted poly(vinyl acetate) (PVAc) has been prepared by UV‐initiated bulk polymerization of monomer at 42°C. Measurements of light‐scattering intensities in the temperature range Tg − 30°C > T > Tg + 50°C have been carried out. Photon correlation spectroscopy has been performed in the temperature range Tg + 5°C > T > Tg + 23°C. Intensity data for T < Tg are in agreement with the Einstein–Smoluchowski expression for density fluctuations, >δρ2; below Tg statistical thermodynamic formulation of >δρ2, evaluated using experimental equation‐of‐state information, is found to be in accord with the light‐scattering results. Photon correlation functions are well described by a single Williams–Watts function. Mean relaxation times and associated activation energies are compared with results of other relaxational studies of PVAc. Discrepancies observed are interpreted to be due in part to variability of sample histories as well as to problems in analytical treatment of the pertinent relaxation spectra.
An essay on the molecular theory of rubber elasticity
Authors: Ullman Robert
Published: June 2010

A discussion of some current ideas on the molecular processes of rubber deformation is presented. Reference is made to some important experiments and to suggestions which have been proposed for their explanation.
Copolymerization: 1. General remarks; 2. selective examples of copolymerizations
Authors: Overberger C. G.
Published: June 2010

Dr. Turner Alfrey was a scientific pioneer in the area of copolymerization. Copolymerization is a polymerization process in which more than the minimum number of monomers required to form a polymer are polymerized together to give a product which has incorporated in it the repeat units corresponding to all the monomers employed, and the products thus obtained are called copolymers. Copolymers can also be produced by employing the mutual reactions of functional polymers or oligomers or their reactions with the appropriate monomers. Both step‐growth and chain‐growth processes, the latter involving a free‐radical, ionic, coordination, or ring‐opening mechanism, can be used to make copolymers.
Spontaneous copolymerizations initiated by tetramethylene intermediates: A new interpretation of charge‐transfer initiation
Authors: Hall H. K. , Padias A. B.
Published: June 2010

Spontaneous addition and polymerization reactions between olefins of different electron densities result in a wide variety of small molecules and polymers. The small molecules include cyclobutanes, 1‐butenes, and pyrans; the polymers can be homopolymers and/or alternating copolymers. Tetramethylenes are proposed as key intermediates in most of these reactions. The tetramethylenes, generated by bond‐forming initiation, are hybrids of 1,4‐biradical and zwitterionic forms. The character is mostly determined by the substituents at the terminals. Zwitterionic character is favored by strong donors such as alkoxy and dialkylamino groups at the carbenium ion end, and strong acceptors such as two cyano groups at the carbanion end. Biradical character is favored by acceptor groups such as diester and cyanoester at the acceptor end, and aryl and vinyl as donor groups. Zwitterionic tetramethylenes initiate ionic homopolymerization, while biradical tetramethylenes initiate alternating copolymerization.

This unifying concept of bond‐forming initiation is extended to spontaneous addition and polymerization reactions of hetero‐atom acceptor molecules and 7,7,8,8‐tetrasubstituted quinodimethanes. Finally, compounds possessing labile σ‐bonds (mainly halogens and peroxides) fit the general scheme. In a few cases, coupling of tetramethylenes may contribute to polymer formation. Ion‐radical pairs, charge‐transfer complexes, and adventitious impurities are excluded as significant initiators.

The bond‐forming initiation has been thoroughly discussed in a recent paper by Hall [1].
Cellular materials: the unending opportunity and challenge for multidisciplinary polymer science
Authors: Rubens L. C.
Published: June 2010

Cellular polymers are important products accounting for about 10% of the global markets for thermoplastic and thermoset materials. During his industrial research career, Turner Alfrey made important contributions to the science and technology of various foams. His studies have not been published elsewhere, but they were pioneering concepts that had a major impact upon the understanding of the continuous extrusion process for polystyrene foams. The included paper entitled “Compression Behavior of Open‐Celled Polyurethane Foams” was intended for presentation at the 1980 Gordon Conference on Foams. This author believes this to be the last scientific paper written by Turner Alfrey.
IPN foams
Authors: Frisch Kurt C. , Sakhpara Dilip , Frisch Harry L.
Published: June 2010

Semirigid IPN foams were prepared by simultaneous polymerization (SIN technique) of urethane‐isocyanurate and epoxy resin systems. Significantly higher compressive strength was obtained with the IPN foams as compared to the corresponding urethane‐isocyanurate foams. Due to the relatively low functionality of the foam components, and hence, resulting low crosslink density of the IPN foams, the oxygen indices and the friability were relatively low but increased with increasing isocyanate index and epoxy content. Although these studies were preliminary in nature, this type of IPN foams could find applications in sound and noise attenuation as well as for energy absorption such as shock and vibration damping.
The role of viscoelasticity in adhesion
Authors: Andrews E. H.
Published: June 2010

This paper demonstrates how a recent formulation of fracture mechanics termed “Generalized Fracture Mechanics” is specially suited to the analysis of adhesive failure since it permits the separation of the interfacial component of adhesion from viscoelastic and other energy losses in the bulk of the adhesive (and/or adherends). The role of such losses can therefore be uniquely defined.
Harmonic modes of a disordered zig‐zag chain
Authors: Halley J. W. , Thorpe M. , Walker A.
Published: June 2010

We describe the results of a simulation of a model of a random chain embedded as a self‐avoiding walk on a diamond lattice. The dynamic model is the same as Kirkwood's. The equation of motion method we use permits such functions as S(k, ω), the dynamic structure factor, to be calculated as easily as the density of states. We present results on the density of states and S(k, ω) for chains of 1000 monomers. The results illustrate a mechanism of harmonic self‐stabilization of a chain, which we also discuss in physical terms. We believe that simulations of this type can be useful to experimentalists in relating spectral features to morphology.
Hydrodynamics of polymer fluids
Authors: Mackley M. R.
Published: June 2010

Experimental systems in which polymer fluids can be examined in different velocity fields are briefly described. The steady‐state predictions of dilute solution theory are examined and their particular relevance to extensional flow experiments discussed. The observed flow behavior of broad‐molecular‐weight distribution polymer melts in different velocity fields is examined, particularly in relation to the apparent connections with the theoretical predictions of dilute solution behavior.
A mean field theory for diffusion‐limited cluster formation
Authors: Muthukumar M.
Published: June 2010

A mean field theory for diffusion‐controlled cluster formation is presented by considering the competition among the different protions of a growing cluster for the incoming diffusive particles. This competition is shown to introduce a screening length that depends inversely on the density of the cluster. The Hausdorff dimensionality D of these clusters is shown to be (d2 + 1)/(d + 1), where dis the eudidean dimensionality. This result is in excellent agreement with that of the computer simulations of Witten and Sander and Meakin. The theory also predicts that the growth of these clusters occurs on their periphery in any d.

PACS nos: 68.70,+ w, 82.70.Dd, 05.70.‐a
Kinetic percolation with mobile monomers and solvents as a model for gelation
Authors: Bansil R. , Herrmann H. J. , Stauffer D.
Published: June 2010

We discuss the results of Monte Carlo simulations of a recent kinetic percolation model applicable to free radical initiated copolymerization of bifunctional and tetrafunctional units in the presence of a solvent. We find that the critical exponent for gelation and the critical amplitudes are unchanged by the inclusion of solvent and mobility. We also obtain relations for the dependence of the critical conversion and the maximum value of the suscepiibility on the fraction of tetrafunctional monomers, solvent concentration, and initiator concentration.
L'importance du processus dans la création d'une équipe de leadership cadre: Une étude de cas
Authors: Zakariasen Kenneth L.
Published: June 2010

Dans un monde où, comme aujourd'hui, les soins de santé sont concurrentiels et en évolution rapide, les organismes ne peuvent pas tolérer un leadership inefficace à long terme s'ils veulent continuer à connaître le succès. Il est très habituel pour les équipes de leadership de se regrouper et de commencer immédiatement à travailler… du moins à tenter d'accomplir le travail que chaque membre de l'équipe croit qu'il doit accomplir. Malheureusement, chaque personne a probablement une idée différente de ce que doit accomplir l'équipe et sur la façon de s'y prendre pour arriver aux résultats escomptés. C'est là une recette certaine d'inefficacité.

Dans l'étude de cas suivante, nous examinons comment l'équipe de cadres dans un collège de sciences de la santé a abordé la création d'une équipe de leadership efficace et décrivons l'importance du processus qui permet de réaliser les résultats escomptés. Le processus ainsi décrit peut servir à n'importe quelle équipe de leadership, mais il doit toujours être adapté aux besoins et aux aspirations uniques de chaque équipe.