bluuebunny/crossref_metadata_2025_split huggingface dataset:
Struktureller aufbau und physikalisches verhalten vernetzter epoxidharze
Authors: Fischer Michael , Lohse Friedrich , Schmid Rolf 
Published: April 2003

AbstractNetwork structures and physical properties of products obtained either by crosslinking polyepoxides with polyphenols, and by dicyanodiamide or by catalytic polymerization are discussed and compared with those obtained by amine or anhydride curing. The highest crosslinking density is achieved by the polymerization of epoxy compounds. In polymerization, the glass transition temperature may rise by more than Δ Tgv = 100 K. Amine and phenol curing result in similarly structured networks with mobile aliphatic segments and comparatively low crosslinking densities. Impact resistance based on dissipation of mechanical energy increases as network density decreases, a maximum being achieved with a medium chain length of 25 – 35 atom intervals between crosslinking points. The mechanical stability of polymers is limited by the cohesive strength KF. This latter corresponds to the maximum shear strength of bonds TKFmax, which was measured within the temperature range of 77 K to 450 K, in accordance with the equation

This equation was derived from Eyring's model of viscosity, correlating B and C with activation volume, activation energy, Tg, and strain rate. B equals the cohesive strength at 0 K. It is determined by intermolecular forces but does not depend on the density of crosslinking. An increase of Tg due to crosslinks or bulky segments causes a decrease of C and therefore a reduction of the temperature dependence of KF. Hence, cohesive strength at room temperature is improved.
Thermotropic liquid crystalline polymers, 4. Study of crystalline and liquid‐crystalline comb‐like polymers with mesogenic side groups by IR spectroscopy
Authors: Shibaev Valery P. , Platé Nicolai A. , Smolyansky Alexander L. , Voloskov Alexander Ya. 
Published: April 2003

AbstractThe IR spectra (in the region of 400–3600 cm−1) of comb‐like polymers in crystalline, liquid‐crystalline, and fluid isotropic phases were studied, and the effect of the chemical structure of the long side chains on the crystalline and liquid‐crystalline states were examined. The spectroscopic criteria of phase transitions in comb‐like polymers were established and the fragments of the side chains involved in the formation of the liquid‐crystalline phase, were determined.
Electrochemical studies of some three component copolymers in nonaqueous media
Authors: Chatterjee S. K. , Pachauri L. S. 
Published: April 2003

AbstractSome three‐component copolymers have been prepared by condensing formaldehyde with each of the following groups of monomeric species: (i) sulfanilic acid + p‐toluidine + p‐bromoaniline; (ii) p‐aminobenzoic acid + p‐toluidine + p‐bromoaniline; (iii) sulfanilic acid p‐aminobenzoic acid + p‐bromoaniline. The composition of the copolymers has been deduced from electrometric titration studies in nonaqueous media, and Br content of the copolymers. Differentiation of acidic functional groups and the degree of polymerization of the copolymers could be obtained from their titration curves.
Study on mechanochemical syntheses of some macromolecular complexes of vanadium and manganese with polyamides and polyester‐polyamides as ligands
Authors: Simionescu Cristofor , Vasiliu‐Oprea Cleopatra , Negulianu Claudia 
Published: April 2003

AbstractPolymeric metal complexes were synthesized mechanochemically by ultrasonic action on mixtures of poly(ethylene terephthalate), ethylenediamine, and vanadium trichloride or by vibratory milling of a mixture of poly(ϵ‐caprolactam) and manganese dichloride (MnCl2·4H2O). The influence of duration of ultrasonic action or vibratory milling as well as the ratio of reagents on the efficiency of complexation was studied. The resulting products were characterized spectroscopically (by IR and ESR spectra), by elemental analyses, and by X‐ray diffraction. They show a relatively high thermostability and semiconductivity.
Untersuchungen zur thermodynamik und konformation von makromolekülen in polymermischungen in der nähe von entmischungspunkten durch neutronenbeugung
Authors: Schmitt Burghard J. , Kirste Rudolf G. , Jelenič Jernej 
Published: April 2003

AbstractThe structure and the thermodynamics of polymer blends made from two poly(styrene/acrylonitrile) copolymers with a different ratio of styrene/acrylonitrile are investigated by neutron scattering. These systems are endothermic, exhibit a positive value for the Huggins parameter χ and show phase separation at sufficiently large molecular weights. The results are in good agreement with the corresponding states theory of Prigogine and Patterson. Other polymer blends are exothermic, exhibit negative χ‐values and are compatible even for infinitely large molecular weights. In these cases one can adapt the theoretical equations to the experiments by the introduction of a suitable parameter for an exothermic contact energy. This is shown for blends from poly(methyl methacrylate) and poly(styrene/acrylonitrile).
Synthèse par voie radicalaire de polymères à extrémités hydroxylées, 7. Synthèse de polybutadiènes: Études cinétiques
Authors: Brosse Jean‐Claude , Legeay Gilbert , Bonnier Maryvonne , Pinazzi Christian 
Published: April 2003

AbstractIt could be shown that radical polymerizations of butadiene in methanol, initiated by hydrogen peroxide, cleaved in two hydroxyl radicals by thermal reaction, give three types of products: oligomers formed predominantly during the two first hours, polymers formed by an autoacceleration phenomenon, mainly during the two first hours, and polymers of high molecular weight, formed after two hours of reaction. The results show that the reaction order is about 1,6. In addition, thermal initiation was also observed.
Coenzyme models, 21. Oxidative trapping of carbanion intermediates by a flavin immobilized in cationic polymers
Authors: Shinkai Seiji , Kusano Yumiko , Manabe Osamu 
Published: April 2003

AbstractAromatic aldehydes 5 and α‐keto acids 8 in the presence of cyanide ion, which usually give the benzoin condensation products, were converted oxidatively to the corresponding benzoic acids 10 by the catalytic action of the title flavin. The change in the reaction route cannot be achieved completely by flavin 1. Product analyses and kinetic measurements established that the carbanion intermediate, \documentclass{article}\pagestyle{empty}\begin{document}${\rm R}\hbox{---} \mathop {\rm C}\limits^ \ominus \left( {{\rm OH}} \right)\left( {{\rm CH}} \right)$\end{document}, which is formed through rate‐limiting deprotonation or decarboxylation of the cyanide‐adducts, is oxidized immediately by the title flavin. The influence of polymer structure on the efficiency of flavin trapping is discussed.
Dielectric behavior of ethylcellulose in concentrated solutions
Authors: Araki Kazuo , Togawa Shigeru , Miyama Tamio , Imamura Yoshio 
Published: April 2003

AbstractMeasurements of dielectric relaxation were made for a series of solutions of ethylcellulose in benzene. The concentrations ranged from 0,5 to 20 wt.‐% and two polymers of different molecular weight were used. The dielectric dispersion was measured over the frequency range of 30 Hz – 3 MHz at 30 – 50°C. The concentration dependence of the critical frequency below and above the critical concentration is interpreted by the free volume effect. It was found that the dielectric relaxation times are constant above the critical concentration and that the activation energy increases with concentration. The observed relaxation time is analyzed by Fröhlich's theory assuming two limiting relaxation times. The lower limit in the relaxation time, τ1, is concentration‐independent above the critical concentration, in contrast to the upper relaxation time τ2, which depends on concentration. These relaxation times, τ1 and τ2, however, are interpreted by the same free volume effect. The unperturbed molecular dimension at the critical concentration is also discussed.
Stufenweise darstellung eines cycloheptamers aus p‐kresol, 4‐tert‐butylphenol und formaldehyd. Vergleich mit einem phenolischen, heptanuklearen kettenoligomer
Authors: Kämmerer Hermann , Happel Günter 
Published: April 2003

AbstractA phenolic cycloheptamer (11) and an analogous chain oligomer (10) with nearly the same structure were gained by stepwise syntheses. The cycloheptamer has a higher melting point and a better solubility in chloroform. In contrast to the chain oligomer his infrared spectrum indicates a stronger association of the hydroxyl groups which is not influenced by the solvent. The mass spectra announce a preferred statistical cleavage along the chain of compound 10 and a great stability of the ring of 11 which preferentially loses his substituents. The 1H NMR spectra confirm the constitutions of the chain (10) and ring compound (11). The cycloheptamer is distinguished by a ring inversion or a pseudorotation, seen by the NMR signals of the methylene protons. The activation energy of the pseudorotation is determined.
Functional polymers, 5. Preparation and polymerization of methyl 4‐vinylsalicylate, 4‐vinylsalicylic acid and 4‐vinylacetylsalicylic acid
Authors: Tirrell David , Vogl Otto 
Published: April 2003

AbstractMethyl 4‐vinylsalicylate, 4‐vinylsalicylic acid, and 4‐vinylacetylsalicylic acid were prepared in overall yields of 28%, 21% and 16%, respectively, starting with 3‐ethylphenol. Radical polymerization of all three monomers was investigated. Methyl 4‐vinylsalicylate and 4‐vinylsalicylic acid polymerized normally via radical initiation, giving soluble polymers of high molecular weight. 4‐Vinylacetylsalicylic acid gave gelled polymerization mixtures in tert‐butanol and in dimethyl sulfoxide, using the same experimental procedure; this was shown to be a result of intermolecular transesterification during polymerization. A water‐insoluble copper complex of poly(4‐vinylsalicylic acid) was prepared. Methyl 4‐vinylacetylsalicylate was also synthesized, in 35% yield, but no polymerization experiments were performed with this monomer. These new polymeric salicylic acid derivatives are of interest as ultraviolet stabilizers, as protective agents for the skin, as metal‐complexing agents, and as potential medicinal agents.
Isotactic poly(allyl vinyl ether), 1. A study of the polymerization and a proposal of a mechanism of stereocontrol
Authors: Sikkema D. J. , Angad‐Gaur H. 
Published: April 2003

AbstractAllyl vinyl ether can be polymerized to highly isotactic polymer with SbCl5 in toluene at ca. −10°C. The stereospecificity is not significantly lower than that of polymer made at ca. −75°C; The reproducibility of the process is greatly improved at the higher temperature. BF3.O(C2H5)2 proved to be an ineffective initiator, in contrast with literature data. NMR analysis, previously published for diads only from NMR data, was performed (1H and 13C) for triads as well, and partly for hexads. No evidence for stereocontrol other than the relationship between active chain end HC⊕OAllyl and incoming monomer can be inferred1cf. Part 2 of this series10.
. A simple mechanism, featuring association between incoming monomer and counterion, invoking only steric hindrance is proposed as an explanation of these findings.
An electron spin resonance study of radical transfer reactions in γ‐irradiated vinylthiol/styrene‐copolymers
Authors: Mönig Hans , Ringsdorf Helmut , Spirk Eugen 
Published: April 2003

AbstractFormation and behaviour of radiation induced free radicals in statistical copolymers from vinyl hydrosulfide and styrene (1:1, 1:4, and 1:10) were investigated by means of ESR spectroscopy. The corresponding homopolymers were also included in these studies. After γ‐irradiation of the copolymers at 77 K and subsequent annealing to 293 K it was possible to detect thio radicals. Their relative yields were found to increase with increasing styrene content. Investigations regarding the thermal behaviour of the radiation induced radicals in the copolymers allowed the assumption of two mechanisms responsible for the formation of the thio radicals: First, the formation takes place via ion radicals located at the mercapto groups at 77K. In the copolymers the stability of the thio radicals is favoured by steric hindrance through the benzene rings thus reducing the formation of disulfide bridges as termination reaction. Secondly, the formation of the thio radicals is caused by a hydrogen transfer from the mercapto groups to the benzyl radicals and/or cyclohexadienyl radicals of styrene units.
Template polycondensation of active esters containing nucleic acid bases with diamines
Authors: Hattori Masahira , Nakagawa Hiroshi , Kinoshita Masayoshi 
Published: April 2003

AbstractTemplate polycondensations of di‐p‐nitrophenyl methylsuccinate derivatives of thymine (1) and theophylline (2) with piperazine and 4‐aminomethylbenzylamine (4‐ABA) were carried out in pyridine/methylene chloride and in DMF solutions. Polystyrenes containing adenine as a side group in various contents were used as template in this polycondensation. The polycondensation reactions of active ester 1 with diamines were effectively accelerated by the presence of the template in both solvents. On the other hand, the polycondensation reactions of active ester 2 with diamines were scarcely affected by the template under the same conditions. The maximum acceleration effect was observed in the presence of templates in which the adenine content is about 54% for the polycondensation of 1 with piperazine and about 25% for that with 4‐ABA, respectively.
Isotactic poly(allyl vinyl ether), 2. An NMR‐study of stereoregularity and relaxation times
Authors: Angad‐Gaur H. , Sikkema D. J. 
Published: April 2003

AbstractThe stereoregularity of poly(allyl vinyl ether), (poly[1‐(allyloxy)ethylene], 1) was studied by both 1H‐ and 13C NMR‐spectroscopy at 6,34 tesla. Even at this field the 1H NMR‐resonances severely overlap, thus hampering a reliable analysis. The situation is far better for the 13C NMR‐resonances; here even hexad splittings could be observed. Relaxation time ratios of the backbone carbon atoms are consistent with a dipolar relaxation mechanism. The relaxation time for the racemic peak is longer than that for the meso peaks, which is in contrast with literature data for other polymers7,8. This deviating behaviour could be accounted for by the higher magnetic field used in our measurements.
On the molecular weight determination by vapor pressure osmometry (VPO), 2. Molecular weight average obtained by VPO
Authors: Figini Ruben Víctor 
Published: April 2003

AbstractProvided that in molecular weight determinations by vapor pressure osmometry (VPO) the relationship between M and the measured quantity (δV/c)c=0 obeys a calibration function of the type (δV/c)c=0 = KM−a, the kind of molecular weight average M̄VPO delivered by this method is derived. The deviation of M̄VPO from the true number average molecular weight M̄n is estimated from its dependence on the polydispersity and the exponent a of the calibration function.
Coordination polymers of β‐hydroxy‐γ‐amino schiff bases
Authors: Jagur‐Grodzinski Joseph 
Published: April 2003

AbstractLigands 3a–d (N,N‐disubstituted 2,2′‐dihydroxy‐3,3′‐[1,4‐phenylenebis(methylenenitrilo)]‐dipropaneamines) for the preparation of the coordination polymers of Ag(I), Cu(II), Zn(II), and Ti(IV) were synthesized by condensation of terephthalaldehyde (2) with the N,N‐substituted 2‐hydroxy‐1,3‐propanediamines (1a–d). The copper and zinc coordination polymers were found to be compatible with polyethylene. Their blends could be processed by injection molding or extrusion. The thermal stability of the polymers was found to increase in the order Cu‐ <Ag‐ <Ti‐ <Zn‐derivatives. The electronic, IR, and ESR spectra of the copper coordination compounds were measured and the mechanism of formation of the coordination polymers is discussed. The polymers were found to be semi‐conductive, their electric resistivity being in the range of 103 − Ω·cm. The temperature dependence of the conductivity yielded activation energies in the range of 26 −106 kJ·mol−1. Both electronic and ionic conductance may contribute to the semiconductive properties of these coordination polymers.
Kinetics of thermooxidation and photooxidation of poly(oxy‐2,6‐dimethyl‐1,4‐phenylene), 1. Analysis of products
Authors: Sláma Zdeněk , Švejdová Emílie , Majer Josef 
Published: April 2003

AbstractThe time dependence of the thermooxidative degradation was measured within the temperature range of 100–150°C. The extent of degradation was characterized by monitoring the content of hydroperoxy, hydroxyl, carbonyl, and quinone groups. Moreover, oxygen absorption, weight changes, and carbon dioxide formation were followed. Calculations of material balance were carried out on the basis of weight changes, oxygen absorption, and analytically determined concentration of oxidation products. The photooxidation was also characterized by the content of hydroperoxy groups and the formation of hydroxyl, ester, and carbonyl groups. A semiquantitative method was employed to determine the concentration of carboxyl groups. In both cases the presence of xanthone moieties was observed. In samples subjected to photooxidation also a small amount of peracids and peresters was found. The mechanism of the degradation processes is discussed in some details.
New polymer syntheses, 3. Binding of nucleosides to basic polypeptides via isocyanato‐isothiocyanates
Authors: Kricheldorf Hans R. , Fehrle Martin J. 
Published: April 2003

AbstractNew aliphatic α‐isocyanato‐ω‐isothiocyanates of various chain lengths were synthesized from ω‐isothiocyanatocarboxylic acid chlorides and trimethylsilyl azide. The 5′‐OH group of 2′‐O,3′‐O‐isopropylideneuridine and of N6‐benzoyl‐2′‐O,3′‐O‐isopropylideneadenosine was added selectively onto the isocyanate group of aromatic and aliphatic α‐isocyanato‐ω‐isothiocyanates. The isothiocyanate group of the resulting nucleoside derivatives was then reacted with the free amino groups of polylysine, isopolylysine, polyornithine and isopolyornithine. The resulting polypeptides with pending nucleosides were characterized by elemental analyses and 360 MHz 1H NMR spectra. A new “one‐pot‐procedure” was developed to protect the primary amino group (N6) of 2′‐O,3′‐O‐isopropylideneadenosine.
Molecular weights and molecular weight distributions of poly(trimethylhexamethyleneterephthalamide) (trogamid T®)
Authors: Herold Julius , Meyerhoff Günther 
Published: April 2003

AbstractMolecular weights of Trogamid T® were determined by ultracentrifugation, light‐scattering, osmometry and viscometry, molecular weight distributions by gel permeation chromatography (GPC) and five different fractionation methods. The separation efficiency of GPC with N,N‐dimethylformamide as solvent was tested with three different types of gels, crosslinked polystyrene, porous glass and crosslinked poly(vinyl acetate), the last one yielding the best results. Solution fractionations show better results than precipitation methods. All fractionations gave far too small apparent non‐uniformities. After correction according to the non‐uniformities of the fractions the results corresponded to those of the other methods. All methods resulted in U = M̄w/M̄n − 1 = 0,7 for the technical product Trogamid T®. The discrepancy to U = 1 of a Schulz‐Flory distribution can be explained by the influence of the path of reaction.
Association and crystallization of poly(ethylene oxide)
Authors: Shimada Toshio , Okui Norimasa , Kawai Thoru 
Published: April 2003

AbstractThe discontinuous change of the lamellar thickness with crystallization temperature was studied for low molecular weight fractions of OH‐terminated poly(ethylene oxide) (PEO). IR analyses demonstrated that almost all of the molecular chain ends were associated in the molten state, whereas a large part of their ends were free in dilute solution. Discontinuous changes were observed for low molecular weight PEO fractions crystallized from the melt, whereas continuous changes were found both for PEO's crystallized from dilute solution and those with phenylated end groups crystallized from the melt. Accordingly, it was pointed out that the association of the end groups could play an important role in the crystallization mechanism and the conformation of the resultant PEO crystals.
Kinetics of alkaline hydrolysis of polyacrylamide in solution by viscosimetric technique
Authors: Gunari Arun A. , Gundiah Subbaraya 
Published: April 2003

AbstractThe alkaline hydrolysis of polyacrylamide in solution is studied viscosimetrically. The viscosity of the solution increases continuously during the course of hydrolysis. The relationship between intrinsic viscosity and the extent of reaction is established, using a series of polyacrylamides with known extents of hydrolysis. The extent of reaction is determined from the observed flowtime, using the relationship between [η] and extent of reaction. The second‐order rate constant and the activation energy are in good agreement with those reported in the literature. A four‐fold increased reactivity of the amide groups towards hydrolysis is observed at very low extents of hydrolysis.
Synthesis and characterization of new polynuclear manganese‐thiolato complexes
Authors: Kaneko Masao , Ishihara Nobuhide , Yamada Akira 
Published: April 2003

AbstractNew polynuclear manganese‐thiolato complexes were prepared by reaction of Mn ions with chelating mercapto compounds, such as 1,2‐dimercaptoethane (DME), 3,4‐dimercaptotoluene (DMT), cystein (Cys), β‐mercaptoethyl alcohol (ME), β‐mercaptoethylamine (MEA), and mercaptoacetic acid (MAA). Potassium permanganate formed stable complexes with DME, DMT and Cys. The complexes of ME, MEA and MAA were prepared by the reaction with manganous chloride. The temperature dependencies of the magnetic susceptibility of the complexes, except Cys, obeyed the Curie‐Weiss law, indicating strong antiferromagnetic interaction between the spins on the Mn ions. The valence of the DME and DMT complexes was calculated to be IV to V, and that of the Cys, ME, MEA and MAA complexes to be II to IV. ESR spectra of the DME and DMT complexes showed broad singlet absorptions, while those of ME, MEA and MAA complexes exhibited narrow Lorentzian singlets, both types indicating strong interaction between the spins. These results and the composition indicated polynuclear complexes containing μ‐oxo (DME and DMT), μ‐chloro or μ‐thiolato (ME, MEA and MAA) structure, while Cys gave mononuclear complex.
Influence of hydroperoxides on the photothermal oxidation of polyethylene
Authors: Ginhac Jean‐Marie , Gardette Jean‐Luc , Arnaud René , Lemaire Jacques 
Published: April 2003

AbstractAccumulation of secondary hydroperoxy groups linked to saturated carbon atoms of polyethylene could be observed by IR spectrophotometry after thermal or photocatalytic oxidation. It was shown that these hydroperoxides have no photoinductive effect on the overall oxidation of polyethylene. Under the same experimental conditions, the situation was found to be opposite in isotactic or atactic polypropylene; the tertiary hydroperoxides formed in thermal oxidation initiate new oxidative reactions.
Stereoregularity of poly(methyl vinyl ketone) and poly(isopropenyl methyl ketone) determined by 13C NMR spectroscopy
Authors: Matsuzaki Kei , Kanai Taiichi , Aoki Yuichi 
Published: April 2003

Abstract13C NMR spectra of poly(methyl vinyl ketone)s (PMVK) and poly(isopropenyl methyl ketone)s (PIPMK) obtained by radical and anionic catalysts were measured. The 13C resonances of the CH2 carbon of PMVK were tentatively assigned to diad tacticities. The spectra of carbonyl carbon and methyl carbon of the CH3CO group of PIPMK were assigned to pentad and triad tacticities, respectively. It is shown that radically obtained PMVK and PIPMK have atactic and syndiotactic‐rich structure, respectively. The stereoregularity of radically obtained PIPMK obeys Bernoullian statistics, while that of anionically obtained PIPMK conforms to first‐order Markov statistics.