bluuebunny/crossref_metadata_2025 huggingface dataset:
Clinical cell therapy imaging using a perfluorocarbon tracer and fluorine‐19 MRI
Authors: Ahrens Eric T. , Helfer Brooke M. , O'Hanlon Charles F. , Schirda Claudiu
Published: September 2014

Purpose

Cellular therapeutics are emerging as a treatment option for a host of serious human diseases. To accelerate clinical translation, noninvasive imaging of cell grafts in clinical trials can potentially be used to assess the initial delivery and behavior of cells.

Methods

The use of a perfluorocarbon (PFC) tracer agent for clinical fluorine‐19 (19F) MRI cell detection is described. This technology was used to detect immunotherapeutic dendritic cells (DCs) delivered to colorectal adenocarcinoma patients. Autologous DC vaccines were labeled with a PFC MRI agent ex vivo. Patients received DCs intradermally, and 19F spin‐density‐weighted MRI at 3 Tesla (T) was used to observe cells.

Results

Spin‐density‐weighted 19F images at the injection site displayed DCs as background‐free “hot‐spot” images. 19F images were acquired in clinically relevant scan times (<10 min). Apparent DC numbers could be quantified in two patients from the 19F hot‐spots and were observed to decrease by ∼50% at injection site by 24 h. From 3T phantom studies, the sensitivity limit for DC detection is estimated to be on the order of ∼105 cells/voxel in this study.

Conclusion

These results help to establish a clinically applicable means to track a broad range of cell types used in cell therapy. Magn Reson Med 72:1696–1701, 2014. © 2014 The Authors. Magnetic Resonance in Medicine Published by Wiley Periodicals, Inc. on behalf of International Society of Medicine in Resonance.
Relaxivity‐iron calibration in hepatic iron overload: Predictions of a Monte Carlo model
Authors: Ghugre Nilesh R. , Doyle Eamon K. , Storey Pippa , Wood John C.
Published: September 2014

Purpose

R2* (1/T2*) and single echo R2 (1/T2) have been calibrated to liver iron concentration (LIC) in patients with thalassemia and transfusion‐dependent sickle cell disease at 1.5T. The R2*‐LIC relationship is linear, whereas that of R2 is curvilinear. However, the increasing popularity of high‐field scanners requires generalizing these relationships to higher field strengths. In this study, we tested the hypothesis that numerical simulation can accurately determine the field dependence of iron‐mediated transverse relaxation rates.

Methods

We previously replicated the calibration curves between R2 and R2* and iron at 1.5T using Monte Carlo models incorporating realistic liver structure, iron deposit susceptibility, and proton mobility. In this paper, we extend our model to predict relaxivity‐iron calibrations at higher field strengths. Predictions were validated by measuring R2 and R2* at 1.5T and 3T in six β‐thalassemia major patients.

Results

Predicted R2* increased twofold at 3T from 1.5T, whereas R2 increased by a factor of 1.47. Patient data exhibited a coefficient of variation of 3.6% and 7.2%, respectively, to the best‐fit simulated data. Simulations over the range 0.25T–7T showed R2* increasing linearly with field strength, whereas R2 exhibited a concave‐downward relationship.

Conclusion

A model‐based approach predicts alterations in relaxivity‐iron calibrations with field strength without repeating imaging studies. The model may generalize to alternative pulse sequences and tissue iron distribution. Magn Reson Med 74:879–883, 2015. © 2014 Wiley Periodicals, Inc.
Z‐score reference ranges for normal fetal heart sizes throughout pregnancy derived from fetal echocardiography
Authors: Li Xinyan , Zhou Qichang , Huang Huan , Tian Xiaoxian , Peng Qinghai
Published: September 2014

Objective

To construct Z‐score reference ranges for normal fetal heart sizes throughout pregnancy.

Methods

This is a prospective cross‐sectional investigation of 809 normal singleton fetuses from 11th week to term. Fetal transverse heart diameter (HD), heart length (HL), heart circumference (HC) and heart area (HA) were derived from two‐dimensional echocardiography. The regression analyses of the mean (M) and the standard deviation (SD) for each parameter were calculated separately, using fetal somatic sizes as independent variables. A group of fetal heart diseases was assessed using these parameters.

Results

Strong correlations were found between fetal heart sizes and somatic sizes. Linear‐cubic regression equations were each fitted to the models of the means of the heart sizes, whereas linear‐quadratic equations were fitted to the models of the SDs. HD was the dependent variable that provided the highest correlation coefficient with all of the fetal sizes, followed by HL, HC and HA. All fetuses with Ebstein's anomaly and most with homozygous α‐thalassemia‐1 demonstrated Z‐scores reflective of increased heart sizes.

Conclusion

The calculation of Z‐scores for heart sizes as a function of fetal somatic size is simple and may be useful for quantitative assessment of some cardiac diseases, particularly cardiomegaly caused by homozygous α‐thalassemia‐1. © 2014 John Wiley & Sons, Ltd.
Inclusion compounds of linear polymers and polymerization of monomers included in perhydrotriphenylene
Authors: Farina M. , Natta G. , Allegua G. , Löffelholz M.
Published: September 2014

The trans‐anti‐trans‐anti‐trans isomer of perhydrotriphenylene C18H30 forms crystalline inclusion compounds with linear macromolecules, such as polyethylene, 1,4‐polybutadiene, and poly(oxyethylene glycol). The main results concerning the constitution, determined by x‐ray diffraction and by differential thermal analysis, as well as the stability of these compounds, are reported here. Moreover, studies were made on the polymerization of various monomers included in PHTP by γ‐rays radiation. In several cases, an inclusion compound of the polymer in PHTP is obtained from such a reaction. A high degree of stereoregularity has been observed for some of the polymers obtained (e.g., polydiolefins); the first reported example of an isotactic polymer obtained by γ‐rays polymerization is due to the above method; it is the isotactic trans‐poly‐1,4‐pentadiene.
Stereospecific polymerization of butadiene by catalysts prepared from π‐allyl nickel halides
Authors: Porri L. , Natta G. , Gallazzi M. C.
Published: September 2014

Butadiene has been polymerized by π‐allyl‐Ni‐halides (I) to low molecular weight stereoregular polymers, with either benzene, n‐pentane, tetrahydrofuran, cyclohexanol, or ethyl alcohol used as solvents. Solid polymers and oily products were simultaneously obtained as polymerization products. In benzene as solvent, π‐allyl‐Ni‐I and π‐allyl‐Ni‐Br gave predominantly trans‐1,4 polymers, while π‐allyl‐Ni‐Cl gave polymers largely composed of cis‐1,4 units. In the other solvents predominantly trans‐1,4 polymers were obtained, irrespective of the nickel derivative used. By reacting π‐allyl‐Ni‐Br, in benzene solution, with either AlBr3, Al2(O‐i‐C3H7)3Br3, BF3 or TiCl2 (O‐i‐C3H7)2, complexes were obtained (II) which polymerize butadiene to predominantly cis‐1,4 polymers. Evidence is reported that these complexes are of ionic type and contain the cation

magnified image

The different stereospecificity observed in the polymerizations by I and II is interpreted on the basis of the different mode of coordination of butadiene to Ni of the complexes I and II, respectively.
Crystal structure of trans‐polypentenamer
Authors: Natta G. , Bassi I. W.
Published: September 2014

trans‐Polypentenamer, like natural rubber, crystallizes under stretching at room temperature. The x‐ray fiber spectra of crystalline trans‐polypentenamer can be interpreted on the basis of an orthorhombic unit cell whose identity periods in A. units are: a = 7.28 ± 0.10; b = 4.97 ± 0.05; c = 11.90 ± 0.10 (chain axis); Z = 4(C5H8); dcalo = 1.049 g./cm.3. Probable space groups C92v(Pna21) or D162h (Pnam). Atomic positions were deduced by trial and error. The (CHCHCH2CH2CH2) monomeric units repeat along a twofold helix. The molecular packing in the crystal state is essentially regulated by the H atoms of the CH2 groups. The packing of the trans‐polypentenamer molecules is very similar to the packing found for orthorhombic polyethylene.
A new method of synthesis of polyhydroxyphenylenes from polyatomic phenols
Authors: Paushkin Ya. M. , Polak L. S. , Omarov O. Yu. , Patalakh I. I.
Published: September 2014

The authors have worked out a method of synthesis of new polymeric polyatomic phenols consisting of elimination of water from diatomic phenols. The reaction was carried out by heating the parent phenols in an autoclave at temperatures from 200 to 350°C. under pressure, in the presence of zinc chloride. The yields varied from 30 to 87%, depending on the reaction conditions. The obtained polymers were soluble or insoluble high melting powders, the molecular weights of soluble fractions ranging from 350 to 2000. Hydroxybenzine was assumed to form as an intermediate product, with consequent polymerization to polyhydroxyphenylenes. With phenol as a starting monomer, the reaction leads to the formation of polyphenylenes. The elementary composition, hydroxylic values, infrared spectra, and electrophysical properties of prepared polymers have been characterized. The number of uncoupled electrons was 1018 sp./g.; the electric conductivity values for typical samples varied from 10−8–10−9 ohm−1 cm.−1; activation energy, 0.12–0.42 e.v. The temperature dependence of conductivity obeys the exponential low.
Untersuchungen zum Einstellvorgang bei osmotischen Messungen
Authors: Philipp B. , Wulf K. , Kapelle R.
Published: September 2014

Die Arbeit befasst sich mit der raschen osmotischen Molekulargewichtsbestimumng von Polyacrylnitril und Cellulosenitrat unter Verwendung cines Zweikammer‐Osmometers, dessen Lösungsmittelzelle mittels eines flexiblen Schlauches mit einem Niveaugefäss verbunden ist. Durch Änderung der Steighöhe des Lösungsmittels unter Konstanthalten der Steighöhe der Lösung, einem im Prinzip seit längerem bekannten, aber bisher kaum konsequent betriebenen Messverfahren, wird die Gleichgewichtsdruckdifferenz sehr schnell angenähert. Der Lösungsmeniskus stellt eine Art “Nullinstrument” dar, wobei es zur Erreichung höherer Genauigkeit aber auch möglich ist, den Gleichgewichtswert von oben und unten einzugabeln. Die kurzen Messzeiten verringern gleichzeitg eine das Ergebnis verfälschende Kurzkettenpermeation in die Lösungsmittelzelle recht wesentlich, was besonders für unfraktionierte technische Produkte von Bedeutung ist.
Properties of polymer solutions
Authors: Rossi C. , Bianchi E. , Pedemonte E.
Published: September 2014

According to the present theories, the Flory‐Mandelkern invariant F should assume values between 1.65 and 1.75 × 10−9 for medium and high molecular weights, and increase up to about 3 × 10−9 for very low molecular weights. By using experimental data on [η], M, and D deduced from the literature, we get a set of scattered F values, ranging from 1.40 to 1.60 and independent of molecular weight. Measurements carried out in our laboratory on polystyrene in benzene and on polyisobutylene and cyclohexane give F values independent of molecular weight in the range 103–105. The dependence of the F values upon the solvent, as observed in our experiments, is explained as due to differences in the effects of the solvent on the viscosity as compared to the diffusion.
Static dielectric properties of dilute solutions containing macromolecules with polar flexible side chains
Authors: Mandel M.
Published: September 2014

The static dielectric properties of polymers in nonpolar solvents are described in terms of homogeneous suspensions of spherical regions each containing a solvated macromolecule. Two models are used. The first one applies to polymers having polar side groups rigidly attached to the main chain or making a constant average direction with respect to the segment to which they are connected. This model yields a conventional relation between the dielectric increment Δ∈, and the mean‐square dipole moment (MSM) of the polymer, so that the molecular weight (M) dependency of MSM and Δ∈ are related. Another model is used for loosely coiled polymers with principal dipoles situated in flexible side groups. From a semimacroscopic calculation, using the assumption that the mean contribution of a given monomeric unit only depends on its average distance to the center of gravity, another expression is derived for Δ∈. For such systems Δ∈ could depend on molecular weight but no direct relation is expected between Δ∈ and MSM or the mean‐square end‐to‐end distance. As a first approximation, Δ∈ is independent of M, as is also found experimentally for poly(methacrylic esters) and poly(vinyl acetate) in various nonpolar solvents. It is shown that the latter model is related to a previously proposed interpretation of the dielectric dispersion for solutions of the same polymers.
Zur Kinetik der Emulsionspolymerisation von Vinylchlorid
Authors: Gerrens H. , Fink W. , Köhnlein E.
Published: September 2014

Es wird eine Dilatometer‐Apparatur aus V2A‐Stahl beschrieben, die mit einem beweglichen Faltenbalg arbeitet und zur Messung von Emulsionspolymerisationen unter Druck geeignet ist. Nach Versuchen mit K2S2O8 als Initiator und C16H33CHOHCH2SO3Na als Emulgator nimmt bei steigender Emulgatorkonzentration [I] die Bruttorekationsgeschwindigkeit vBr proportional [I]0,8 zu, während die Teilchenzahl N konstant bleibt. Bei steigender Temperatur bleibt N konstant und vBr nimmt entsprechend einer Bruttoaktivierungsenergie von 24,2 kcal/mol zu. Bei kleinen Emulgatorkonzentrationen [S] steigt N proportional [S]1,2 und vBr ändert sich nicht. Diese Ergebnisse lassen sich mit der Smith‐Ewart Kinetik erklären, wenn man eine Abbruchsreaktion von 1. Ordnung in Bezug auf aktive Radikale annimmt und berücksichtigt, dass in diesem Falle die Volumenwachstumsgeschwindigkeit eines Latexteilchens nicht konstant ist, sondern mit [I] zunimmt. Abbruch durch Monomeres lässt sich mit den Versuchsergebnissen nicht vereinbaren. Abbruch durch Einschluss von Radikalen und Abbruch durch desaktivierende Kettenübertragung auf das Polymere in Nachbarschaft zu einer durch HCl‐Abspaltung gebildeten Doppelbindung werden diskutiert. Bei hohen Emulgatorkonzentrationen nehmen vBr und N beide proportional [S]0,6 zu. Diese Abhängigkeit lässt sich mit Smith‐Ewart Kinetik und monomolekularem Abbruch nicht erklären.
Polymerisation de l'Isoprene en Presence de Strontium
Authors: Kistler Jean‐Paul
Published: September 2014

The reaction was examined as a function of the nature and origin of the finely divided metal, prepared either by regeneration from its NH3 complex or by mechanical pulverization in an inert atmosphere. Isoprene (99%) was distilled over Na and prepolymerized on Li to give 99.8% purity (determined by gas chromatography). The reactions were performed in the absence of O2 at 21°C. for 65 hr. with a Sr concentration of 2%. The structure of polymers was determined by NMR. It is independent of the temperature of formation and decomposition of the Sr–NH3 complex and of the by‐products formed by decomposition of the complex.
On the phenomenological description of the nonlinear deformation behavior of rubberlike high polymers
Authors: Becker G. W.
Published: September 2014

The theoretical relationships for the description of the nonlinear deformation behavior of solids can be controlled rather easily by measurements on rubberlike polymers, because of the very small time dependence of their mechanical properties, and because of their large strain range. The data of recent investigations of the biaxial stress–strain behavior of a natural rubber are used for the evaluation of the gradients of the strain energy function given by Rivlin. It is demonstrated that even for a material for which the assumption of incompressibility is practically valid, the actual mechanical behavior is described much too complicated especially in the region of smaller deformations.
Diastereoisomeric compounds as possible models for stereospecific polymerization
Authors: Corradini P. , Paiaro G. , Panunzi A.
Published: September 2014

The stereoregular polymers of monoolefins arise from the polymerization of vinyl compounds, which do not have a symmetry plane perpendicular to the plane of the double bond. The generation of diastereoisomeric complexes when an olefin is coordinated to an asymmetric center is the first step of a polymerization process, leading to stereoregular polymers. When olefinic compounds with a symmetry lower than 2mm are coordinated to a transition metal in simple complexes, enantiomeric mixtures are obtained. The resolution of such a type of asymmetry was achieved via fractional crystallization of diastereoisomeric mixtures with an asymmetric ligand. The study of properties of cis and trans π‐complexes of the type [olefin‐Pt‐dichloro‐α‐phenethylamine] gave evidence that the formation of the cis complexes involves a remarkable asymmetric induction also in solution. Complexes of Fe(CO)4 with unsaturated carboxylic acids were also resolved.
Elektronenmikroskopische Untersuchungen an hochpolymeren Lösungen
Authors: Ruscher Ch.
Published: September 2014

Mit Hilfe der Methode der Gefriertrocknung erhält man Präparate, die den Zustand von Hochpolymeren in Lösung zu untersuchen gestattet. Für Cellulosenitrat in Butylacetat und für Polycarbonat in Methylenchlorid wird der Lösungszustand nach verschiedenen Lösezeiten demonstriert. Lösungen mit molekular gelösten Stoffen konnten ebenfalls gefunden werden. Aus solchen Aufnahmen konnte für Polycarbonate, für Polystyrol und für Polyacrylnitril jeweils ein Molekulargewicht bestimmt werden, das hinreichend genau mit den anderweitig bestimmten Werten übereinstimmt.
Étude éxpérimentale de la Conductivité en Courant continu des Composés macromoléculaires
Authors: Yu L. T. , Borredon M. S. , Jozefowicz M. , Belorgey G. , Buvet R.
Published: September 2014

Lors des études de conductivité en courant continu, en fonction de la température, effectuées sur des composés macromoléculaires dopés par des substances gazeuses, il est nécessaire de s'assurer que le taux de dope du matériau constituant l'éprouvette de mesure reste constant pendant toute la durée des mesures. On décrit un dispositif expérimental de conditionnement de l'éprouvette de mesure permettant le maintien à une valeur constante du taux d'hydratation d'un polymère hydrophile, lorsque la température varie. Les résultats relatifs aux polyamides, au polyacrylonitrile, et aux sulfates d'éméraldine obtenus avec l'aide de ce dispositif sont reproductibles avec une bonne précision; ces résultats montrent que l'eau absorbée a une influence prédominante sur la valeur de la conductivité de ces polymères. Dans le cas des sulfates d'éméraldine hydratés on montre que la conductivité est sans ambiguïté d'origine électronique; néanmoins l'influence de l'eau est considérable. On en conclut que le fait que l'eau absorbée ait une influence sur la conductivité d'un polymère hydrophile ne saurait constituer une preuve excluant le caractère électronique de celle‐ci.
Paramagnétisme de Complexes à Transfert de Charge Macromoléculaires
Authors: Andre J. J. , Weill G.
Published: September 2014

On a étudié comparativement la résonance paramagnétique électronique des complexes d'éthyldiméthylaniline et de polydiméthylaminostyrène avec le chloranile à l'état solide et dans des solvants de polarité différente. Le polymère et l'élément de répétition donnent des signaux peu différents (valeur de g, largeur de raie, saturation). Cette identité permet néanmoins de préciser l'origine moléculaire du paramagnétisme à l'exclusion de défauts de réseau. L'exaltation du signal par irradiation optique révèle qu'il doit être dû à la paire d'ions‐radicaux dont le temps de recombinaison est de l'ordre de 10−4 sec. L'influence du solvant peut jouer soit sur la fraction ionique à l'état fondamental, soit sur l'énergie relative des niveaux singulet, biradical et triplet de la paire d'ions‐radicaux.
Relations entre Indice de Fluidite à Chaud, Viscosité à l'État Fondu, Viscosité Intrinsèque et Température pour le Poly(éthylène Térèphtalate) et pour un Poly(éthylène Térèphtalate) Partiellement Modifié
Authors: Manaresi P. , Giachetti E. , De Fornasari E.
Published: September 2014

Methods for the determination of melt index and melt viscosity of poly(ethylene terephtalate) (PET) were performed. Measurements of melt index at different temperatures and of melt and intrinsic viscosity were carried out on laboratory samples. Relations have been obtained and theoretically interpreted among the above parameters. These relations allowed us to utilize melt index data in order to estimate melt viscosities and molecular sizes of PET. Melt indexes were found to be inversely proportional to newtonian melt viscosities. The relations among intrinsic viscosity, melt viscosity, and melt index, respectively, were found to be linear in a log‐log plot. The effect of temperature on melt index values was found to agree with the Andrade equation. The energy of activation of the viscous flow was calculated and showed a slight dependance on molecular weight.

Measurements were also carried out on an adipic acid–terephtalic acid–ethylene glycol copolymer. It was possible also in this case to obtain relations among the above parameters which were similar to the ones obtained for PET. However, the melt viscosity of the copolymer was always lower than the one of PET at the same intrinsic viscosity. This effect was attributed to an increase in chain flexibility.
Mechanismus und Kinetik der Poly‐∈‐caprolactam‐Bildung unter Berücksichtigung von Amidin‐Zwischenstufe
Authors: Csürös Z. , Bertalan Gy. , Nagy J. , Trézl L. , Körösi J.
Published: September 2014

The most important reaction of the polycaprolactame formation is the lactame addition under ring opening on the end groups. This reaction, in accordance with Körösi's data, is composed of two consecutive steps: the condensation of and ∈‐caprolactame, forming amidine salt and water reaction products and, the hydrolysis of amidine salt. To find if, amidin formation is a general part of cationic polycaprolactame formation, research work has been carried out in two directions:

Oligomer studies. Equimolar mixture of caprolactame and of n‐butylamine HCl, has been studied to obtain amidine salt intermediate in the oligomer mixture. The formed amidine salt, N‐[1‐aza‐cycloheptene‐(1)‐yl‐(2)]‐butylamin. HCl has been identified by thin‐layer chromatography. Some additional chemicals, such as phosphorpentoxide, increase the quantity of amidine salt in the fusion. Other additional agents, however, such as water of some acids, can cause it to decrease or disappear completely.

Kinetic studies. The stability of the amidine salt had been investigated, aqueous solution of N‐[1‐aza‐cycloheptene‐(1)‐yl‐(2)]‐butylamin. HCl having been used as initiator. According to our supposition, the amidine salt reacts with water in two directions. groups necessary for polymer‐formation are formed in the course of these reactions. The products of the reaction are butylamine‐HCl and caprolactame, as well as N‐(∈‐amino caproyl)‐butylamine HCl. 1 mole active end group is formed from 1 mole of amidine salt and 1 mole of water. In other words, concerning water content, 1 mole of butylamine. HCl corresponds to 1 mole of amidine salt + 1 mole of water. It could be verified that the mixture of butylamidine. HCl and water initiates the same lactame transformation as the corresponding amount of butylamin. HCl, if more than 1 mole % has been taken. It could be shown that the velocity constant of the amidine formation is less, or much less, than that of the amidine hydrolysis. Considering an amidine intermediate stage in the formation of polycaprolactame released by water or by proton acids, we consider the deduct ion of a new and unified kinetic as probable.
Optically active vinyl polymers. XIV. Stereoselective and stereoelective polymerization of racemic α‐olefins
Authors: Pino Piero , Ciardelli Francesco , Montagnoli Giorgio
Published: September 2014

Polymers of racemic 4‐methyl‐1‐hexene, 3‐methyl‐1‐pentene, and 3,7‐dimethyl‐1‐octene have been separated in fractions having optical activity of opposite sign by adsorption chromatography on highly crystalline poly‐(S)‐3‐methyl‐1‐pentene. It is shown that the observed prevalence of S or R monomeric units in the optically active polymers thus obtained cannot be explained on the basis of a model of a purely statistical copolymer of the two monomeric antipodes. This conclusion is confirmed by the fact that at‐acticpoly‐(R)(S)‐4‐methyl‐1‐hexene, obtained by hydrogenation of poly‐(R)(S)‐4‐methyl‐1‐hexyne prepared with a substantially soluble catalyst, has not been separated in fractions having optical activity of opposite sign in the adopted experimental conditions. The reported results prove that the stereospecific polymerization of the above‐cited racemic α‐olefins by heterogeneous catalysts is stereoselective, giving rise to macromolecules formed prevailingly by one single monomeric antipode. On the basis of the experimental results obtained in the stereoselective and stereoelective polymerization of racemic α‐olefins, the structure of the catalytic centers of the heterogeneous catalysts for the stereospecific polymerization of α‐olefins is discussed.
Optically active vinyl polymers. XV. The optical activity in hydrocarbon solution of poly[(s)‐1‐methyl propyl]vinyl ether and of poly[(s)‐2‐methyl butyl] vinyl ether
Authors: Pino Piero , Lorenzi Gian Paolo , Chiellini Emo
Published: September 2014

The molar rotatory power in hydrocarbon solution of poly[(S)‐1‐methyl propyl]vinyl ether (I) is far higher than that of poly[(S)‐2‐methyl butyl]vinyl ether (II). With increasing temperature, the molar rotatory power of (I) decreases greatly, whereas that of (II) increases very slightly. The comparison of O.R.D. of (I) and (II) in the absence of complexing agents and in the presence of Al(i‐C4H9)3 with that of low molecular weight model compounds has allowed some reasonable hypotheses to be drawn which explain, at least in part, the different behavior shown by the two polymers, and suggest that the relationships between optical activity and polymer structure are qualitatively the same in polyvinyl ethers and poly‐α‐olefins. The change of rotation of polyvinyl ethers by complexation with Al(iC4H9)3 is qualitatively consistent with the behavior of the low molecular weight models and, at least in the case of (II), dependent on polymer stereo‐regularity.
Molecular weight distributions from turbidimetric titrations
Authors: Bryce W. A. J. , Meldrum I. G.
Published: September 2014

The molecular weight distribution of the products of the reaction between polystyryl potassium and 1,3,5 tri[bromomethyl] benzene was determined by turbidimetric technique. For the system chloroform–ethanol–polystyrene (anionic) the solubility S of a species of molecular weight M at a volume fraction γ of nonsolvent is given by the expression

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The polymerization of chloroprene. III. Characteristics of the initiation process in thermal polymerization
Authors: Billingham N. C. , Leeming P. A. , Lehrle R. S. , Robb J. C.
Published: September 2014

The observed activation energy for the thermal polymerization is shown to be the same as that for the simple dimerization reaction. This provides additional support for our conclusion that the latter process is controlling the rate of the thermal polymerization, which proceeds by consecutive reactions where the initial formation of dimers is followed by their subsequent polymerization. Present experiments further suggest that traces of peroxide are responsible for the initiation of this so‐called thermal polymerization, and the results indicate limits within which the “thermal” rate is controlled as above. Conventional free‐radical initiators are unable to initiate the polymerization of dimers, but with this exception the system displays several features characteristic of a free‐radical process, e.g., in its behavior toward inhibitors and UV irradiation. Kinetic measurements on initiated monomer systems suggest specific initiation of the monomer itself, and incidentally illustrate that there is surprisingly little cross‐propagation of dimers. The implications of the results are discussed.
Alkyl derivatives of pyrocatechol as stabilizers in γ‐irradiated polypropylene
Authors: Nechitailo N. A. , Sanin P. I. , Polak L. S. , Pospisil J.
Published: September 2014

Studies were conducted of the stabilizing effect of dialkyl derivatives of pyrocatechol types I–III and 2‐alkoxyphenol types IV and V in polypropylene irradiated under vacuum with a dose of 110 or 228 Mrad. It was found that some derivatives, particularly those containing a bulky tertiary butyl group in o the position to the hydroxyl group, retard the destruction of the polymer and formation of crosslinks, protecting at the same time irradiated polypropylene against subsequent oxidation. In the studied series of pyrocatechol derivatives the structural dependencies are well visible although the interpretation of results is probably also affected by the direct action of γ‐radiation on the stabilizers.
A route to sulfur—nitrogen polymers containing eight‐membered rings
Authors: Heal H. G. , Kane J.
Published: September 2014

The condensation of disulfur dichloride with any one of the three positional isomers of hexasulfur diimide gives rise to linear polymers in which eight‐membered sulfur–nitrogen rings derived from the diimide are coupled together by S2 groups. From the 1,5‐diimide a single homologous series arises; we have isolated its first four members. Rings derived from the 1,3‐diimide can couple cis‐ or trans‐ to one another; we have isolated cis‐ and trans‐forms of the two‐ring coupling product and observed their spontaneous interconversion. Rings of the 1,4‐diimide are optically asymmetric; we have isolated diastereoisomers of the corresponding two‐ring coupling product, and a mixture of isomers of the three‐ring homolog.
Molecular motions in poly‐α‐methylstyrene
Authors: Baccaredda Mario , Butta Enzo , Frosini Vittorio , Magagnini Pierluigi , Andruzzi Fulvio
Published: September 2014

Dynamic mechanical properties (sound velocity and damping factor) have been determined in poly‐α‐methylstyrene in the temperature range from 60 to 470°K., at frequencies in the range 103 ÷ 106 Hz. Two high dissipation regions are found in the damping‐temperature curves: one, at temperatures below Tg, characterized by a loss peak at about 140°K., and another, at temperatures above Tg (405°K.), characterized by a very rapid increase of losses with increasing temperatures. The loss peak at low temperature (δ) is probably due to rotational motions of the phenyl rings in the side chain; the corresponding activation energy is about 4000 cal.‐mole−1, much higher then that of polystyrene, because of the sterical hindrance of CH3 in the α position. A δ transition is also found in other vinyl polymers containing aromatic groups as side chains: by plotting the logarithm of the activation energy as a function of the reciprocal maximum damping temperature, determined in different polymers, points nearly lying on a straight line are obtained. The main transition is associated with cooperative motions of chain segments. Practically no difference is found between the dynamic mechanical properties of atactic and syndiotactic samples of poly‐α‐methylstyrene.
Effect of structure and thermal prehistory on molecular order and relaxation properties of rubberlike polymers at low temperatures
Authors: Bartenew G. M. , Zelenev Yu. V.
Published: September 2014

The effect of thermal prehistory on relaxation mechanical and dielectrical properties of rubberlike polymers has been studied by varying the conditions of heating and cooling of the specimens. The annealing of specimens by slowly cooling heated specimens, as well as amorphization, which occurs when heated specimens are cooled rapidly, results in a marked change in the dependence of dynamic characteristics in the glassy and the viscoelastic state on temperature and frequency. Annealing and amorphization of specimens alter the temperature interval in which deformation is dependent on frequency affect the magnitude of the dynamic modulus at constant frequency over a wide temperature range, and also result in a non‐uniform variation of the modulus difference at the maximum and minimum external frequencies.

The shape of the maxima of mechanical losses in the low‐temperature principal and auxiliary relaxation regions observed in the case of annealed and amorphized specimens is different from that of the initial rubber. Since variations in the thermal prehistory cause no alteration in the molecular structure of rubbers, the phenomena observed can be attributed only to rearrangement of supramolecular structures.

Variations in thermal prehistory exert no effect on the shape of the maxima of dipoleelastic dielectric losses because changes occur only in the mobility of segments with polar side groups, whereas the motion of supramolecular structures is absent. Density of the space network and the type of vulcanization (heat vulcanization at elevated temperature or radiation vulcanization at 20°C.) likewise influence the molecular order in rubberlike polymers and the dependence of the mechanical loss factor on temperature.
Synthesis and polymerization studies of some N‐alkylol acrylamides. II. Polymerization and copolymerization of 2‐methacrylamido‐2‐hydroxymethyl‐1,3‐propanediole
Authors: Jedliński Z. , Paprotny J.
Published: September 2014

A study has been made of the radical polymerization and copolymerization of 2‐methacrylamido‐2‐hydroxymethyl‐1,3‐propanediole with styrene at 60°C. This monomer homopolymerizes easily in water solution, yielding polymers of high molecular weight, but at high conversion crosslinking occurs. A further detailed kinetic investigation in dimethylformamide resulted in values for the overall rate of polymerization that were comparable to values for other acryl monomers. For copolymerization of 2‐methacrylamido‐2‐hydroxymethyl‐1,3‐propanediole (M1) with styrene (M2) in dimethylformamide solution, the reactivity ratios r1 = 0.47 and r2 = 1.29 were obtained.
Polymerization of unsaturated methyl‐α‐d‐glucopyranoside acetals. I
Authors: Jedliński Zbigniew , Maślinska‐Solich Jolanta
Published: September 2014

The effectiveness of several cationic initiators for the polymerization of 4,6‐acrylidene‐methyl‐α,d‐glucopyranoside has been examined. The most effective initiators found for polymerization acrylidene‐methyl‐α,d‐glucopyranoside are cationic catalysts. Some properties of new polymers were investigated. Moreover some oligomeric acetals of methyl‐α,d‐glucopyranoside and acrolein have been separated and their structures have been proposed.
Radiation effects in polypropylene and ethylene–propylene copolymers
Authors: Odian George , Lamparella Don , Canamare Joseph
Published: September 2014

The effect of radiation on various propylene and ethylene–propylene copolymers has been followed by observing the gel fraction as a function of radiation dose. The G (crosslink) and β/α values were calculated from the solubility data and are discussed in terms of the polymer composition. Allyl methacrylate was found to greatly increase the efficiency of radiation crosslinking of both polypropylene and an ethylene–propylene copolymer.
Polymerization of α‐methylstyrene by naphthylsodium
Authors: Podolsky A. F. , Korotkov A. A.
Published: September 2014

The kinetics of the polymerization of α‐methylstyrene by naphthylsodium at −78°C. in tetrahydrofuran has been studied for elucidating the mechanism of the polymerization. The experimental relationships obtained are accounted for by an assumption that the polymerization proceeds by the “coordination” mechanism and 4 elementary reactions take place: (1) generation of the active centers of polymerization; (2) chain propagation; (3) chain termination; (4) reaction of chain propagation upon the organometal compounds formed as a result of the termination reaction (upon the “living” polymers).

This latter reaction proceeds without termination. In solving kinetic equations reduced time φ = ∫0τ m · dτ is introduced here m is the monomer concentration and τ is the time. The apparent values of the constants of elementary reactions are determined from the dependence of the number‐average degree of polymerization \documentclass{article}\pagestyle{empty}\begin{document}$ \[\bar p\] $\end{document} on the initial catalyst concentration n0 and from the dependence of conversion X on reduced time φ. The coincidence of the expected relationship X = F(τ,φ) with those experimentally found was traced with an electronic computer over all the range of X values. Equations are derived for the dependence of the polymerization rate upon the initial concentration of the catalyst and for the molecular weight distribution of the polymer. Experimental points appear to agree with the calculated data. The curve of the molecular weight distribution has 2 maxima.
Studies on the kinetics of polyesterification
Authors: Vancso‐Szmercsányi I. , Makay‐Bödi E.
Published: September 2014

The polyesterification reaction in relation to proton catalysis was studied. The polycondensation reactions of maleic, fumaric, phthalic, succinic, adipic, and sebacic acids with various glycols were studied in the melt without catalysts. The results were classified into two groups. In the first group belong those reactions which proceed in the initial stage at a considerably greater rate than in the main stage, which kinetically is second order. The reactions of acids with greatly differing first and second dissociation constants, and with a high first dissociation constant, belong into this group. Acids with a relatively small difference between their first and second dissociation constants and a lower first dissociation constant belong in the second group. A reaction order of 2.5 was obtained for these acids. To provide evidence for a correlation between the auto‐catalytic effect and the dissociation constant, maleic and fumaric acids were esterified with methyl alcohol both with and without a foreign acid catalyst.
Solid state polymerization of several monomers by vacuum ultraviolet rays
Authors: Tabata Yoneho , Kadoi Hajime , Oshima Keichi
Published: September 2014

Solid state polymerization of acrylonitrile and acetylene initiated by a vacuum ultraviolet radiation (Xenon resonance line, 8.44 e. v.) has been studied at low temperatures in a range of −100 to −196°C. The color of polymers obtained ranged from nearly white to brownish yellow. It was found from infrared spectra of the polymers that the structure of the polyacrylonitriles obtained by vacuum ultraviolet irradiation is quite different from that of the polyacrylonitriles obtained by γ‐rays or accelerated electrons irradiation. In the polymers obtained by γ‐rays, the nitrile groups remain unreacted but in the case of vacuum ultraviolet the number of unreacted nitrile groups decreases with decreasing polymerization temperature. It may be concluded that in the case of vacuum ultraviolet irradiation the polymerization reaction takes place both in nitrile and vinyl groups, and thus the ring is formed by an intramolecular linkage. The apparent activation energy was obtained from the initial rate as 3.1 kcal./mole (−100 to −130°C.) and 0.06 kcal./mole (−130 to −196°C.). The quantum yield in the polymerization at −196°C. was estimated to be about 0.2 and the G value was about 2. G value in γ‐ray‐initiated polymerization at −196°C. was 102 ∼ 103. The extreme differences between the G values may be attributed to the energy differences of radiations for the initiation reaction.
Mechanismus der Dreidimensionalen Polymerisation von Glykolmethacrylaten
Authors: Kopeček J. , Jokl J. , Lím D.
Published: September 2014

The three‐dimensional, homogeneous, and heterogeneous polymerizations in systems monoglycol or diglycol monomethacrylate–dimethacrylates of glycols in various solvents were studied dilatometrically. The network density and the content of pendant vinyl groups were determined at various conversions. The influence of physical crosslinks formed by hydrophobic crosslinking agents was estimated by the comparison with copolymers of diglycol monomethacrylate–methyl methacrylate. By correlation of kinetics of polymerization with the three‐dimensional network formation, it was possible to characterize the polymerizing systems within the whole range of conversion.
On the charge carriers mobility in polymers
Authors: Kryszewski M. , Szymański A. , Światek J.
Published: September 2014

In the case of polymers a direct determination of charge carriers mobility based on Hall constant measurements is impossible. Therefore, the theory of space charge‐limited current, which enables charge carriers mobility calculation, was applied. Transient space charge‐limited currents were investigated in thin films (13–150 μ) of polyvinyl chloride and of copolymer of acrylonitrile with 2‐vinylpyridine. Measurements were carried out at room temperature. The calculated mobility of charge carriers is within 10−3 to 10−4 cm.2/v. sec.
The theory of branching processes and kinetically controlled ring—chain competition processes
Authors: Gordon M. , Scantlebury G. R.
Published: September 2014

The statistical theory of branching processes provides unified and powerful methods for calculating statistical parameters, especially for branched polymer systems. A review of some recent calculations provides examples such as the sol fraction, molecular weight and configurational size averages, and the concentration and mean length of active network chains in f functional random or nonrandom polycondensations. The theory furnishes a useful approximation to the calculation of thermodynamically or kinetically controlled ring–chain competition processes in branched systems.
Étude de la Distribution des Compositions au Sein de Copolymères Préparés Par Voie Radicalaire
Authors: Herz Jean , Decker‐Freyss Danielle , Rempp Paul
Published: September 2014

The instantaneous composition of a radically prepared copolymer is a function of the composition of the monomer mixture. Thus, if a copolymerization is carried out to give a high yield, the obtained copolymer is not homogeneous in composition. In the present paper, it has been tried to relate the fluctuations in composition within a copolymer sample with the copolymerization yield, knowing the reactivity ratios of the two corresponding monomers. Integration of the Skeist equation, which expresses in a differential form the copolymer composition as a function of copolymer yield, has been performed by means of an electronic computer, for three different monomer systems: styrene—methyl‐methacrylate, styrene—p‐bromostyrene, and styrene—α‐vinyl‐naphthalene. Copolymerization experiments were carried out to various yields, and followed by careful characterization of the obtained products, by analysis, fractionation and UV spectroscopy. The obtained results concerning composition distribution within the samples and the average composition of the copolymers as well are in satisfactory agreement with the corresponding data theoretically established in the first part of the work.
Structure and reversible deformability of oriented crystallizing polymers
Authors: Slutsker A. I. , Sanphirova T. P. , Yastrebinskii A. A. , Kuksenko V. S.
Published: September 2014

The effect of reversible (elastic) extensions of oriented crystallizing polymers on long periods within them, recorded by small‐angle x‐ray diffraction, has been investigated. The reversible shift of the meridian maximum of diffraction intensity toward small angles (which means the increase of long periods) as well as the maximum diffraction intensity increase with polymer loading have been established. The agreement of relative increments of long periods and polymer‐specimen dimensions is rather common, although some instances when the period deformation exceeded the specimen deformation have been observed (for highly annealed oriented polymers). The invariability of crystallites with polymer extension (according to large‐angle x‐ray diffraction) indicates that the deformation of long periods, which are formed by the alternation of crystalline and amorphous regions along the orientation axis, is caused by crystallites transference due to stretching the amorphous interlayers between them. The increase of small‐angle diffraction intensity with the extension of oriented polymers is supposed to be due to two factors: (1) the reduction of crystallite share in long periods; and (2) the decrease of the density of extended amorphous interlayers which results in increasing the density difference of alternate crystallites and amorphous regions. The problem of more precise definition and checking of these conclusions is raised and attention is drawn to the great interest in investigating the amorphous‐region properties in oriented crystallizing polymers, which determine the mechanical properties of polymers.
Untersuchungen über die Eigenschaften hochvernetzter Polymerer mit Hilfe der mechanischen Relaxation
Authors: Pohl G. , Kästner S.
Published: September 2014

In this paper we report on the mechanical behavior of maleic acid hexandiol polyester cured with styrene. The measurements show a broad relaxation region which is composed of two components. To explain this result we must consider the structure of the polyester resin. Besides polyester chains we also have polystyrene maleic acid copolymer chains. Both components give a specific contribution to the mechanical relaxation behavior, but simultaneously a strong interaction to each other.
Spectrophotometric titration of polymethacrylic acid
Authors: Michaeli Isaac
Published: September 2014

Optical density measurements were performed on aqueous solutions of polymethacrylic acid (PMA) at different degrees of neutralization with NaOH, both in the presence and absence of added Na2SO4; the wavelength region studied was 188–250 mμ. The data could be consistently interpreted in terms of an equilibrium between two conformational states of the macromolecules. The distribution of the total monomeric units and of the charged groups between the two states could be spectrophotometrically determined; this provided the necessary information for the evaluation of the titration curves of each conformational state separately. Free energies of transition from the “low pH” form to the “high pH” form, at zero ionization, were derived from the above data, and found to be of the order of one kT unit per monomer.
Small molecule—Protein interactions and the conformation of serum albumin
Authors: Arvidsson E. O.
Published: September 2014

Previous studies on small molecule—protein interactions by the present author and studies on the denaturation of serum albumin by Gorbacheva et al. and by Janatová indicate that the tertiary structure of the native serum albumin molecule does not represent the thermodynamically most probable conformation. It is suggested that the amino and carboxyl groups of the albumin molecule are locked into positions which are metastable with respect to solvent, probably by means of the S—S bonds. The resulting intramolecular interactions (“salt bonding”) in serum albumin then affect intermolecular interactions as manifested by its “abnormal” binding properties. These interactions should also be considered when discussing “abnormal” titration and denaturation properties as an alternative to masking of groups and/or heterogeneity.
Magnetic susceptibility as an application to the study of order—disorder phenomena in polymers
Authors: Calleja F. J. Baltá
Published: September 2014

The diamagnetic susceptibility of differently prepared polyethylene samples was measured. The application of an expression for the molecular susceptibility based on Pascal's additivity law permits the calculation of intermolecular constants associated with different physical states. Treatments such as hot and cold drawing or crystallization from the melt or solution give rise to susceptibility values χ corresponding to intermediate degrees of order between those of the pure “gaseous” and the pure “crystalline” state. Chain folding does not affect the χ values. Chain branching provokes an increase of χ, indicative of a decrease of order.