bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of spin trapping technique to radical polymerization, 11. Initiation and propagation mechanisms for alternating copolymerization of styrene with maleic anhydride
Authors: Sato Tsuneyuki , Abe Masao , Otsu Takayuki 
Published: April 2003

AbstractThe initiation mechanism for spontaneous alternating copolymerization of styrene (St) with maleic anhydride (MAn) was investigated by means of spin trapping technique. using 2‐methyl‐2‐nitrosopropane (7) as spin trapping agent. By means of ESR spectroscopy of the system St/MAn in ethylbenzene, a cyclic radical (13), produced via the Diels‐Alder intermediate 25, was detected as its aminyl oxide. A similar radical was also trapped from the system p‐methyl‐St/MAn and p‐dimethylamino‐St/MAn. It is formed faster in these systems than in the system St/MAn. In chloroform, however, two types of initiating radicals. 13 and the α‐styryl radical (15), were trapped. This indicates that these radicals are produced via 25 and the charge transfer complex 27, respectively. From these results an initiation mechanism is proposed. To clarify further the propagation mechanism, the spin trapping technique was applied to the system, which is initiated by tert‐butoxyl radical formed from di‐tert‐butyl peroxalate (8). The effect of the concentration of 7 on the ESR spectrum of the system St/MAn/8 shows that 27 also participates in the propagation of this alternating copolymerization. Finally, the high reactivity of 27, as compared with free monomers in alternating copolymerization systems, was attempted to be explained on the basis of the Evans‐Polanyi theory.
Die Bestimmung der Molekulargewichtsverteilung von nichtkristallisierenden Polymeren mit dem Elektronenmikroskop, 6. Fehlerkorrektur der experimentellen Zahlenverteilungsfunktion
Authors: Koszterszitz G. , Greschner G. S. , Schulz G. V. 
Published: April 2003

AbstractA mathematical treatment is described, by means of which the effect of the measuring errors on the number molecular weight distribution of polymers, as obtained with an electron microscope (EM), can be eliminated. It is shown, that the difference in the nonuniformities of the measured and the corrected distribution would be negligible only in the case of samples with high average degrees of polymerization and sufficiently broad distributions. Otherwise differences of 10% or more can be found, depending on the size of the actual measuring error. This is shown by means of four practical examples. For a practical application the measuring error may not exceed some critical value, which, though always lies above the mean error of the EM‐method.
The α‐CH proton chemical shift in the coil conformation of poly(L‐alanine)
Authors: Asakura Tetsuo , Ando Isao , Nishioka Atsuo 
Published: April 2003

AbstractIn order to clarify the cause of the change of the α‐CH proton chemical shift through the helix‐coil transition of poly(L‐alanine), the α‐CH chemical shift in a coil form was calculated by taking into account the intramolecular shielding effect and compared with the value in a helical form.The coil α‐CH peak was predicted to resonate upfield by about 0,1 ppm from the helical peak in contrast to the downfield shift observed in experiments. Thus it was suggested that the observed low field shift in trifluoroacetic acid (TFA) mainly comes from the solvent effect by TFA including the rearrangement of the charge distribution along the poly(L‐alanine) chain.
Reaktive copolymere des N‐vinyl‐2‐pyrrolidons zur immobilisierung von enzymen
Authors: Manecke Georg , Korenzecher Rafael 
Published: April 2003

Abstract1‐Vinyl‐2‐pyrrolidone was copolymerized with maleic acid anhydride, with acrylic acid, and with tyrene respectively, using 1,4‐divinylbenzene as crosslinking agent. By polymeranalogous reactions isothiocyanato‐ and diazo groups were introduced into the styrene copolymers, respectively, and azido groups into the acrylic acid copolymers. These reactive, insoluble, hydrophilic carriers were used for the immobilization of enzymes by covalent binding. The copolymers, particularly their ability to immobilize papain as well as their enzymatic activity, were investigated.
Mehrparameterkorrelationen zur quantifizierung der kationischen copolymerisation von styrol undp‐substituierten styrolen
Authors: Heublein Günther , Wondraczek Reinhard 
Published: April 2003

AbstractFor cationic copolymerization of styrene andp‐substituted styrenes the experimental aim values, ratio of monomer reactivity ratios (log(r1/r2)) and average degrees of polymerization (log P̄), can be connected by linear multiparameter equations with parameters characterizing the influence of monomer structure (Δσp), solvent (ET), the reaction temperature (T) and the catalyst activity (χkat.; εGlas/Kat.). The equations allow qualitative and partially quantitative predictions for the selectivity of the cross‐propagation reaction in the copolymerization (log(r1/r2)).
Alternating copolymerization of acrylonitrile with butadiene in the presence of binary and ternary catalytic systems of Lewis acids type
Authors: Florjańczyk Zbigniew , Kuran Witold , Pasynkiewicz Stanisław , Kasprzak Elżbieta 
Published: April 2003

AbstractAcrylonitrile (AN) and butadiene (BD) were copolymerized in the presence of binary C2H5AlCl2MtXn (MtXn = metal halide or metal alkoxide) and ternary ZnCl2RmMtXnVOCl3 (RmMtXn = metal alkyl or alkylmetal chloride) catalytic systems. The yield of the copolymer (mole ratio of units AN/BD = 1:1) formed in the presence of the above systems, and the effects of the molar proportion of catalyst components, of the reaction temperature and time on the copolymer yield in some systems were determined. The role of individual components of binary and ternary catalytic systems in the copolymerization is discussed.
Elektrokinetische untersuchungen an fasern, 2. Experimentelle untersuchungen
Authors: Aichele Wilfried , Schollmeyer Eckhard , Herlinger Heinz 
Published: April 2003

AbstractAn apparatus is described to measure streaming‐potentials as well as streaming‐currents at different concentrations of the solid. Zeta‐Potentials calculated according to Smoluchowski's equation can be corrected by conductance measurements using Ag/AgCl‐electrodes directly in dilute aqueous solutions containing more than 10−3mol/l KCl. They are in good agreement with the real dependence of zeta‐potentials from the “porosity” of the plug. For KCl concentrations smaller than 10−3mol/l, this correction must be done separately from measurements of streaming‐potential according to the method of Fairbrother and Mastin at higher electrolyte concentrations.Among the different porosities given by Konzeny‐Carman, Goring and Mason, Biefer and Mason, and Fairbrother and Mastin, the latter describes best the dependence of the zeta‐potential on the concentration of solid for any kind of plug. These results and the limits of the approximation method are discussed.
Analyse der phasenstruktur von binären polymersystemen
Authors: Henkel Georg , Schindlbauer Hellmuth 
Published: April 2003

AbstractTwo sets of polymer blends have been prepared by mixing solutions or melts of polystyrene with polybutene‐1(poly(1‐ethylethylene)), cellulose acetate, poly(methyl methacrylate), polyisobutylene, atactic polypropylene, poly(vinyl chloride), high pressure polyethylene, and of poly(vinyl chloride) with high pressure polyethylene, ABS, poly(vinylidene chloride), poly(vinyl acetate), vinyl chloride/vinyl acetate copolymer. The phase structure of these blends was analysed by microscopic and differential calorimetric measurements and by determination of the turbidity of the films. Phase diagrams were prepared from the glass transition temperatures and melting points taken from DSC curves. In this analysis all systems show a distinct phase separation ensuing from incompatibility. The only exception is the blend: poly(vinyl chloride) + vinyl chloride/vinyl acetate copolymer.
Growth mechanism of crystals of glycine/S‐methyl‐L‐cysteine copolymer in the course of polymerization
Authors: Kim Kea Yong , Kōmoto Tadashi , Kawai Tohru 
Published: April 2003

AbstractIn order to examine the growth mechanism of copolymer crystals formed during polymerization, the heterogeneous copolymerization of glycine N‐carboxy anhydride (2,5‐dioxo‐1‐oxa‐3‐azacyclopentane) and S‐methyl‐L‐cysteine N‐carboxy anhydride (4‐methylthiomethyl‐2,5‐dioxo‐1‐oxa‐3‐azacyclopentane) was studied in acetonitrile. In all the polymerization systems, the crystal growth occurs through formation of the cross‐β‐type structure. The high conversion in the glycine‐rich systems is accounted for by the widening of the cross‐section of the β‐chain in the backbone crystal, due to the introduction of S‐methyl‐L‐cysteine residues into the polyglycine chain. On the other hand, the narrowing of the cross‐sectional area per chain in the skeleton crystals of the oligomer gave rise to the lowering of the conversion in the S‐methyl‐L‐cysteine‐rich systems. This shows the importance of the effect of the cross‐sectional area of the oligomer chain (of the β structure) in the crystal formed in the begining relative to that of the growing (α‐helical) chain. The glycine residue seems to be incorporated into the crystalline lattice of the S‐methyl‐L‐cysteine and vice versa.
Die γ‐induzierte copolymerisation von vinylfluorid und vinylidenfluorid
Authors: Ellinghorst Guido , Vierkotten Detlev , Hagiwara Miyuki , Hummel Dieter O. 
Published: April 2003

AbstractThe 60Co‐γ‐induced copolymerization of vinyl fluoride (VF) and vinylidene fluoride (VF2) was investigated for the polymerization temperatures 273 K, 253 K, and 233 K. The dependency of the over‐all reaction rate and the over‐all activation energy on the composition of the monomer feed is evaluated. The copolymerization parameters were determined as r1=5,23 and r2=0,06 (VF≙M1). The change of over‐all reaction rate with monomer feed is discussed. By means of a mathematical treatment of the kinetical behaviour of non‐steady‐state reactions, which was modified for the case of copolymerization, the influence of termination and propagation on the over‐all reaction rate was determined separately.
A comparison of the absolute reactivity of monomers, 1. Kinetic study of radical polymerization of acrylamide and methacrylamide, initiated by manganese(III) acetate
Authors: Elayaperumal P. , Balakrishnan T. , Santappa M. 
Published: April 2003

AbstractThe kinetics of polymerization of acrylamide (AAM) and methacrylamide (MAM) with manganese(III) acetate as thermal initiator was studied. In the temperature range between 303 and 313 K, the initial rate of polymerization follows the relation:

The rate of initiation of the polymerization was determined from the rate of decomposition of manganese(III) acetate. The reactivity of the two monomers under the same conditions was compared.
A study of structural order in various polyethylenes at elevated temperatures
Authors: Preedy John E. , Wheeler Ernest J. 
Published: April 2003

AbstractChanges in several structural properties of an ethylene homopolymer have been measured and compared with those of ethylene copolymers with simple and complex branchings over a range of temperature from ambient to above the normal [melting temperature]. In the case of the first two polymeric types, a clear behavioural pattern was observed in which, with rising temperature, a small rotation of the back‐bone chains was followed by melting and recrystallization, the latter two processes occurring in the range from about 110°C to the melting temperature. In the upper temperature range ethyl branches were also rejected from the crystalline lattice. Around the melting temperature, a change from the orthorhombic to the hexagonal phase was suggested as a possibility. The thermal behaviours of the copolymers with the more complex branchings were found to be more complicated with melting and recrystallization occurring over various temperature ranges. No simple relationship appeared to exist between the numbers and shapes of the complex branchings and the structural changes produced in the copolymers by increasing temperature.
Ionische polymere aus 1,4‐bis(chloracetyl)piperazin und difunktionellen tertiären aminen durch quaternisierende additionspolymerisation
Authors: Weiss Josef , Schindlbauer Hellmuth 
Published: April 2003

AbstractNew water soluble polyelectrolytes were prepared by quaternizing addition polymerization of 1,4‐bis(chloroacetyl)piperazine (1) with N,N,N′,N′‐tetramethylhexamethylenediamine (2), 1,4‐dimethylpiperazine (3), 1,4‐diazabicyclo[2,2,2]octane (4), and N,N‐dimethyl‐(4‐dimethylaminomethyl)benzylamine (5). DMF, DMF/water, and water were used as reaction media. The polymer synthesized from 1 and 2 in DMF/water (4:1) showed a very high molecular weight and an intrinsic viscosity of 37ml/g, which is the highest value found for such compounds so far.
Syntheses and properties of poly(iminoethylene) containing nucleic acid bases
Authors: Shimidzu Takeo , Konishi Yoshiyuki , Murakami Akira 
Published: April 2003

AbstractPoly{N‐[2‐(adenin‐9‐yl)ethyl]iminoethylene hydrochloride‐co‐iminoethylene} (1) and poly{N‐[2‐(thymin‐1‐yl)ethyl]iminoethylene hydrochloride‐co‐iminoethylene} (2) were synthesized by alkylation of poly(iminoethylene) with 9‐(2‐chloroethyl)adenine and 1‐(2‐chloroethyl)thymine, respectively. In addition, the alkylation of a commercial poly(ethylenimine) with 9‐(2‐chloroethyl)adenine was carried out. These model compounds interact with nucleosides to form the complementary base pairs. In contrast to that, the order of interaction of those model compounds with nucleotides is the following one: purine‐purine >purine‐pyrimidine>pyrimidine‐pyrimidine. The addition of salt compensates the interaction between 1 and Ado‐5′‐P completely, whereas that between 1 and Urd‐5′‐P is only slightly reduced. This shows that complementary base‐base interaction is not appreciably affected by ionic strength.
Über die druckabhängigkeit der viskoelastischen und physikalisch‐chemischen eigenschaften von polymeren, 3. Darstellung des druckeinflusses auf das spezifische volumen im technischen temperatur‐ und druckbereich
Authors: Karl Veit‐Holger , Asmussen Frithjof , Ueberreiter Kurt 
Published: April 2003

AbstractA reduction formula for the calculation of the specific volume v at any temperature T and any pressure P is derived; it consists of the two equations:

The parameters ξ, ζ and ψ can be easily calculated from values in the literature, and therefore only a volume‐temperature curve at atmospheric pressure has to be measured.
Viskositäts‐molekulargewichts‐beziehung für polyamid‐12
Authors: Hammel Reinhart , Gerth Christian 
Published: April 2003

AbstractLight‐scattering and viscosity measurements were performed on dilute solutions of polyamide‐12 in 1,1,1,3,3,3‐hexafluoro‐2‐propanol at 25°C. The [η]‐M̄w relationship was determined to be [η]=8,43·10−4·M̄w0,68 dl g−1.
Untersuchungen zur Thermolyse und zur Sauerstoff‐Stabilität der 4π + 2π‐Diels‐Alder Addukte des Styrols
Authors: Kauffmann Harald Friedrich 
Published: April 2003

AbstractThe 4π + 2π‐Diels‐Alder cycloadduct 1 involved in the spontaneous polymerization of styrene was investigated under conditions, where bimolecular reactions with styrene leading to a consumption of 1 can be neglected. For this reason 1 was (a) submitted to thermolysis in an inert solvent (toluene) at different temperatures (90, 100 and 110°C) and (b) oxidized with an excess of oxygen in styrene at room temperature. The reactions were followed spectrometrically at the wavelength λ = 325 nm and analyzed in terms of a first order reaction. The results show strong evidence for the involvement of two diastereomers (1a and 1b) of different reactivity. This is in qualitative and quantitative agreement with the two isomers' concept, which had been deduced previously from kinetic analysis of the formation of 1 during the thermal polymerization of styrene. Rate constants and activation energies as well as possible reaction pathways are given.
13C NMR sequence analysis, 10. Synthesis and spectroscopic characterization of sequence polypeptides containing taurine, γ‐aminopropanesulfonic acid, and sulfanilic acid
Authors: Kricheldorf Hans R. , Schultze Joachim 
Published: April 2003

AbstractStarting with benzyloxycarbonyltauryl chloride (1) and benzyloxycarbonylsulfanilyl chloride as well as with glycine ethyl ester and β‐alanine methyl ester several Z‐tripeptides (3a–c, 7a–d) were synthesized. The sulfanilyl peptides 7a–d were converted to the 4‐(isothiocyanato)benzenesulfonyl dipeptides 9a–d, which were condensed to the sequence polymers 10a–d at 140–170°C. From the Z‐tauryl peptides 3a–c the free tripeptides 5a–c were prepared and condensed to the ternary sequence polypeptides 16a–c using the phosphorus triazolides 13 and 14 as condensing reagents. Starting with dipeptides 4a–d and 6a–d the binary sequence polymers 15a–d and 17a–d were obtained in like fashion. The 1H NMR spectra of these oligo‐ and poly‐peptides were recorded in trifluoroacetic acid and 13C NMR spectra of the polypeptides in dimethyl sulfoxide and trifluoroacetic acid. Both 1H NMR and 13C NMR spectra allow characterization of and clear distinction between isomeric oligopeptides, i.e. Z‐Sulf‐Gly‐β‐Ala/Z‐Sulf‐β‐Ala‐Gly, and isomeric polypeptides, i.e. poly(Tau‐γ‐Abu)/poly(γ‐Aps‐β‐Ala) or poly(Tau‐Gly‐β‐Ala)/poly(Tau‐β‐Ala‐Gly). A change of the solvent from dimethyl sulfoxide to trifluoroacetic acid results in a downfield shift of the 13C‐carbonyl signals of the sequence polypeptides by about 10ppm, whereas the other C‐signals show only small effects (<2ppm). The influence of monomer structure, sequence, and solvent on chemical shift is discussed.
Polymere imidazolcarbonsäuren, 2. Über das schwermetallionenbindungsvermögen von chelatharzen mit 4,5‐sicarboxyimidazolyl‐gruppen
Authors: Manecke Georg , Schlegel Rainer 
Published: April 2003

AbstractThe swelling behaviour, the time‐dependence of the uptake of Cu2+‐ions, and the pH‐dependence of the uptake of Cu2+‐, Ni2+‐, Cd2+‐, Zn2+‐ and Mg2+‐ions of crosslinked poly[1‐(4,5‐dicarboxy‐1‐imidiazolyl)ethylene] (1) and poly{1‐[p‐(4,5‐dicarboxy‐2‐imidazolyl)phenyl]ethylene} (2) were investigated. Both resins have a high selectivity for heavy metal ions. For resins 1 the uptake of heavy metal ions in the presence of an excess of EDTA was studied. Furthermore the possibility to remove Hg2+‐ions from aqueous alkalichloride solutions by resin 1 was investigated.
Kinetics of the reaction of a glycol with a diisocyanate
Authors: Yilgör İskender , Orhan Erdal H. , Baysal Bahattin M. 
Published: April 2003

AbstractThe reaction between poly(ethylene oxide) glycol (α‐hydro‐ω‐hydroxypoly(oxyethylene)) and methylenebis(1,4‐cyclohexylene) diisocyanate was studied at 70, 80 and 90°C. The course of the reaction was followed by determining the isocyanate content of the reaction mixture at appropriate time intervals. The data thus obtained were analyzed by taking into consideration the glycol‐ and urethane‐catalyzed reactions separately. It was found that although the urethane‐catalyzed reaction was faster in the temperature range studied, its relative importance decreased with increasing temperature.
Radical reactions initiated by chelate complexes of transition metals, 17. Solvent effect on polymerization of methyl methacrylate initiated by copper(II) 2‐aminoethanolate
Authors: Mapunda‐VlčKová Jana , Bartoň Jaroslav 
Published: April 2003

AbstractThe solvent effect on radical Polymerization of methyl methacrylate initiated by copper(II) 2‐aminoethanolate (Cumea) or by the system Cumea‐reducing agent (H2NCH2CH2OH, CCl4) is discussed. In the first case, where the initiating radical is formed from a Cumea‐MMA complex, the solvent influences the equilibrium of the complex‐forming reaction and thus also the initiation reaction. Further, in this system also primary radical termination and degradative chain transfer are operative. In the initiation by the system Cumea‐reducing agent, the non‐ideal course of polymerization is due to primary radical termination and degradative chain transfer.
Additive effect of poly(ethylene oxide), 1 acceleration effect of poly(ethylene oxide) in several nucleophilic reactions
Authors: Hirao Akira , Nakahama Seiichi , Takahashi Mitsuru , Yamazaki Noboru 
Published: April 2003

AbstractThe additive effect of poly(ethylene oxide) (PEO) in several nucleophilic reactions, such as the oxidation of trans‐stilbene with potassium permanganate, the alkylation of potassium acetate and diethyl benzylsodiomalonate as well as the Williamson reaction of sodium phenoxide with alkyl bromides was investigated and compared with that of dibenzo‐18‐crown‐6 (crown ether). A marked effect by PEO was observed under certain conditions, which was explained by a cooperative coordination of the oxygen atoms of PEO with metal cations promoting ion dissociation and resulting in the observed remarkable rate acceleration.
Polybutadiènes hydroxytéléchéliques, 1. Microstructure, fonctionnalité et mécanismes réactionnels. Etude par résonance magnétique nucléaire du proton et du carbone 13
Authors: Fages G. , Pham Q. T. 
Published: April 2003

AbstractThe examination of H2O2‐initiated hydroxytelechelic polybutadienes polymerized by H2O2 initiation by 1H NMR and 13C NMR allows the identification of three main primary alcoholic groups: α‐unsaturated, β‐substituted/α‐unsaturated and γ‐unsaturated. From 1H NMR accumulated spectra, it has been possible to calculate the number average OH‐functionalities of the polymers. These should be slightly under‐estimated because of the possible presence of secondary and tertiary alcoholic groups whose concentrations, however, should be very small. The nature of these alcohol functions gives information concerning the likely initiation, transfer and termination mechanisms of the radical polymerization of butadiene by H2O2 in alcoholic media.
Studies on aqueous polymerization of acrylonitrile. Cerium(IV)/acetaldehyde redox system
Authors: Ahmed K. Riaz , Natarajan L. V. , Anwaruddin Q. 
Published: April 2003

AbstractThe thermal polymerization of acrylonitrile initiated by the cerium(IV)/acetaldehyde (A) redox system was carried out at 25°C, and the rate of monomer disappearance, –d[M]/dt, was followed by gravimetry and the rate of cerium(IV) disappearance –d[Ce(IV)]/dt by titrimetry. –d[M]/dt was found to be directly proportionsl to [M]3/2, [A]1/2, and [Ce(IV)]1/2. –d[Ce(IV)]/dt was found to be directly proportional to [Ce(IV)] and [A]. A reaction scheme is given together with the kinetic expressions. The activation energy for the overall rate was found to be 67,24kJ.mol−1 (16,06kcal.mol−1), and the value of the second order rate constant kr, was obtained as 2,481.mol−1s−1.
Linear oligopeptides, 48. Synthesis, characterization and conformational analysis in solution of monodisperse protected homo‐oligomers derived from L‐norleucine
Authors: Bonora Gian Maria , Toniolo Claudio 
Published: April 2003

AbstractA series of N‐ and C‐protected L‐norleucine homo‐oligomers from dimer to heptamer was prepared by the dicyclohexylcarbodiimide and acyl azide coupling methods. In the course of the synthetic approach tert‐butyloxycarbonyl as the N‐protecting and methoxy as the C‐protecting end groups were employed. The monodisperse oligomers synthesized in this manner were characterized and found to be chemically pure. A polarimetric investigation in a structure disrupting solvent also indicated that all reactions proceeded with complete retention of the configuration. By UV absorption and far‐UV CD it was shown that these peptides may exist in predominantly β‐form, statistical coil, or partially folded conformation depending upon molecular weight and nature of solvent.