bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymers containing enzymatically degradable bonds, 4. Preliminary experiments in vivo
Authors: Kopeček Jindřich , Cífková Irena , Rejmanová Pavla , Strohalm Jiří , Obereigner Blahoslav , Ulbrich Karel 
Published: April 2003

AbstractCopolymers of N‐(2‐hydroxypropyl)methacrylamide containing oligopeptidic sequences either in side chains or as part of crosslinks were prepared. These polymers were applied intravenously to rats, and spectrophotometric analysis (oligopeptidic side chains) or gel permeation chromatography of urine (oligopeptidic crosslinks) have shown that both types of polymers are cleavable in vivo.
Polymere schiff‐basen‐chelate und ihre vorstufen, 3. Synthese polymer gebundener N3O2‐chelate durch N‐alkylierung niedermolekularer schiff‐basen
Authors: Aeissen Henning , Wöhrle Dieter 
Published: April 2003

AbstractN‐Alkylation of low molcular N3O2‐ligands (2a, b) with several chloromethylated polystyrenes (1a–e) leads to covalently polymer bound Schiff's base ligands (3a–f), which react with Co2+ to polymer bound N3O2 chelates (10a–f). A second route to 3c starts from 1b and the N3‐ligand 5 over the polymer diamine 7. The corresponding low molecular compounds were also prepared.
Ritter's reaction of poly(acrylonitrile)
Authors: Janout Václav , Čefelín Pavel 
Published: April 2003

AbstractThe course of Ritter's reaction of atactic poly(acrylonitrile) with N‐hydroxymethylamides of acetic, benzoic and benzenesulfonic acids and with N‐hydroxymethylimides of succinic, phthalic and o‐sulfobenzoic acids were examined in tetramethylene sulfone under conditions where benzyl alcohol, isopropyl alcohol and triphenylmethanol appear as nonreactive. The reaction systems have a stronger tendency towards crosslinking than that exhibited under comparable conditions by solutions of poly(N‐benzamidomethylacrylamide), poly(N‐phthalimidomethylacrylamide) and poly(N‐o‐sulfobenzamidomethylacrylamide) prepared as reference standards by the solution polymerization of the N‐substituted acrylamides in methanol with dibenzoyl peroxide as initiator.
The structure of poly(N‐vinylcarbazole) obtained with cationic initiators and electron acceptors as catalysts
Authors: Kawamura Tokiji , Matsuzaki Kei 
Published: April 2003

AbstractPoly(N‐vinylcarbazole)s, [poly(l‐(N‐carbazolyl)ethylene)s], (PVCz's) were prepared under various polymerization conditions. The stereoregularities were estimated by means of 13C NMR spectroscopy. Although the stereoregularity of the polymers obtained by BF3O(C2H5)2 was hardly changed by the polymerization temperature, it changed with the solvent polarity from an isotactic‐rich configuration in toluene and CH2Cl2 to a syndiotactic‐rich configuration in nitrobenzene. The 13C NMR spectra of the polymers obtained by organic electron acceptors, support the conclusion that the polymerization by tetracyanoethylene, p‐bromanil, 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone, and tetrachlorophthalic anhydride proceed by a cationic mechanism. In the polymerization of N‐vinylcarbazole (VCz) with maleic anhydride as an electron acceptor, a small amount of copolymer was obtained together with the homopolymer of VCz. Although the structure of the homopolymers is the same as that of the radically obtained polymer, it is considered that the polymer is formed by a cationic mechanism. The polymerizations of VCz by inorganic compounds, such as ferric nitrate, cupric nitrate, cupric bromide, etc., as catalysts are cationic.
Polymerization of lactams, 40. Acceleration of the anionic polymerization of 2‐pyrrolidone
Authors: Patil Vishvanath S. , Roda Jan , Králíček Jaroslav 
Published: April 2003

AbstractThe effect of transient cooling of the polymerization mixture on the anionic polymerization of 2‐pyrrolidone initiated with potassium 2‐pyrrolidonate (2‐oxo‐1‐pyrrolidinylpotassium) prepared in situ and activated with N‐acetyl‐2‐pyrrolidone was investigated. It was found that an increase in conversion and molecular weight is controlled by the time interval between the onset of polymerization and transient cooling of the mixture, unlike an isothermal arrangement of the experiment. The possible mechanism by which the polymerization process is affected is discussed.
Copolymers of 2‐acrylamido‐2‐methylpropanesulfonic acid and aromatic vinyl compounds as potential media for photosensitized electron transfer reactions
Authors: Morishima Yotaro , Itoh Yoshihiro , Nozakura Shun‐ichi 
Published: April 2003

AbstractIn an expectation as potential media for photosensitized electron transfer reactions, polymers carrying both strong electrolytic and hydrophobic segments were prepared by the copolymerization of 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) and styrene. The AMPS segments were found to have a remarkable power to solubilize the hydrophobic segments into water, i.e., even a copolymer with a styrene mole fraction of 0,72 is still soluble in water. Salt effect on the reduced viscosity, broadening of NMR spectra in D2O, and enhanced excimer fluorescence of styryl groups in aqueous solution indicated a pronounced hydrophobic interaction of a number of styryl groups along the chain in the copolymer with high styrene content. 8‐Anilinonaphthalene‐1‐sulfonic acid, 1,6‐diphenyl‐1,3,5‐hexatriene, and a cyanine dye were used as fluorescent probes for the hydrophobic microdomains. The results suggested that the microdomains are highly hydrophobic in nature but less capable to solubilize the fluorescent probes than the surfactant micelles. An electron microscopic image of the copolymer was also discussed as a supporting evidence for the presence of microdomains.
Elementarprozesse löslicher ziegler‐katalysatoren. Polymerisationskinetische analyse und mathematische modellierung im system Cp2TiPropylCl/AlEtCl2/ethylen
Authors: Fink Gerhard , Zoller Welf 
Published: April 2003

AbstractThis paper deals with the kinetics of the polymerization of ethylene catalysed by the soluble Ziegler‐catalyst Cp2TiPropylCl/AlEtCl2. By means of a special method it was possible to study the kinetics of the initial instationary homogeneous part of the polymerization. The dependences of the initial rates on the catalyst components prove that the polymerization active species is formed in two successive very dynamic equilibria. The primary complex equilibrium is entirely located on the right hand side, whereas the second equilibrium depends considerably on the ratio of the catalyst components and is shifted on the active species side only at very high Al/Ti ratios. Because of this location of the two successive equilibria the dependence of the polymerization velocity vp on the charged Al concentration (that is, the Al isotherm) has to show a sigmoidal curve course in the inital part, which experimentally is confirmed exactly. Finally, this extensive kinetical analysis leads to the complete reaction scheme of the polyreaction and by mathematical modelling to the quantitative calculation and description of the experimental curves and dependences (e.g., Al‐isotherm).
Zur copolymerisation von ethylen und α‐olefinen mit ziegler‐katalysatoren
Authors: Böhm Ludwig L. 
Published: April 2003

AbstractStarting with four reaction equations which are at least necessary to describe the copolymerization of two monomers, equations for the kinetics and the molecular weight regulation with and without hydrogen are derived. The equations are used to evaluate the results of the copolymerization of ethylene and 1‐butene. The numerical values of the reactivity ratios r differ by approximately 3 orders of magnitude, but do not depend on whether the molecular weight is regulated by hydrogen or not. The rate of polymerization is scarcely influenced even by great amounts of 1‐butene. It depends nearly completely on the concentration of ethylene. On the other hand the comonomer enormously influences the average molecular weight of the copolymer. This influence increases with hydrogen content.
Polychelates derived from 4,4′‐(4,4′‐biphenylylenebisazo)di(salicylaldehyde oxime)
Authors: Rana Arjun K. , Shah Navnit R. , Patil Manak S. , Karampurwala Asger M. , Shah Jayant R. 
Published: April 2003

AbstractPolychelates of Ni(II), Co(II), Cu(II), Zn(II), and Mn(II) were synthesized from bis 4,4′‐(4,4′‐biphenylenebisazo)di(salicylaldehyde oxime) and metal chlorides. All the chelates are dark in colour and insoluble in common organic solvents. Their most probable structures were determined by visible reflectance spectroscopy and magnetic measurements in conjunction with thermogravimetric and IR measurements. Elemental analyses indicate a ligand: metal ratio of 1:1 and the association of water molecules with the central metal. The decomposition temperatures of the polychelates decrease in the following order: Zn(II) > Co(II) > Ni(II) > Mn(II) > Cu(II).
Recherche de télomères à activité pharmacologique potentielle, 4. Réactions sur les télomères de l'alcool vinylique
Authors: Bauduin Gérard , Bessière Jean‐Marie , Bondon Daniel , Martel Jacques , Piétrasanta Yves 
Published: April 2003

AbstractChlorides of carboxylic acids were grafted on telomers of vinyl alcohol. The yields of grafting were improved by increasing the temperature and the concentration of the reactants. In the range investigated, they do not depend on the DPn of the telomers, nor on the stoichiometric rates of the reactants. Therefore, the grafting rates are directly related to the initial conditions of the reaction. Modification of the telomers by treatment with ethylene oxide provides more soluble substances, but it does not affect the behaviour of the telomers in grafting reactions. Grafting of 1‐(p‐chlorobenzoyl)‐5‐methoxy‐2‐methyl‐3‐indolacetic acid (9) (indomethacin), an antiinflammatory drug, leads to potentially pharmacologically active telomers.
Functional monomers and polymers, 92. Synthetic application of the dehydrating and desulfhydrylating activity of chloropyrimidine derivatives, particularly of the immobilized derivative
Authors: Kondo Koichi , Hyodo Kenji , Murakami Mikio , Takemoto Kiichi 
Published: April 2003

AbstractChloropyrimidine derivatives were found to be useful as active dehydrating and desulfhydrylating reagents for the preparation of carbodiimides, isothiocyanates, esters, lactones, amides, or nitriles. Particularly a polystyrene‐bound reagent was quite useful also due to the advantage of isolating the products easily by using a simple filtration technique. The following decreasing order of reactivity was found: 4‐chloro‐2‐pyrimidone bound to polystyrene (poly{1‐[4‐(4‐chloro‐2‐oxo‐1,2‐dihydro‐1‐pyrimidinyl)phenyl]ethylene}) (5a) ≃ 4‐chloro‐1‐cyclohexyl‐2‐pyrimidone (3a) > 2,4,6‐trichloropyrimidine (2a) > 2,4‐dichloropyrimidine (1a) ≫ 9‐benzyl‐6‐chloropurine (4a). The reactivities are related to the structure, and an enhanced ease of lactim‐lactam tautomerism in the products is suggested as driving force of the reaction.
Dunkel‐ und photoleitung polymerer cyaninfarbstoffe
Authors: Koßmehl Gerhard , Bocionek Peter 
Published: April 2003

AbstractAn equipment for measuring the photoconduction of polymeric material is described comprehensively. The electrical dark conductivities (σ ≤ 2,5 · 10−9 Ω−1 · cm−1) and the photoconduction (Iphot ≤ 2,0 · 10−10 A) were studied for polymeric cyanines and corresponding model compounds. Photoconduction was measured as a function of temperature, current, wavelength, and intensity of the used light.
Graft copolymerization of methyl methacrylate on chlorinated natural rubber, 2. Initiation by tetrakis(trialkylphosphite)nickel
Authors: Nogues Pierre , Dawans François , Maréchal Ernest 
Published: April 2003

AbstractThe kinetics of the graft copolymerization of methyl methacrylate (MMA) initiated by the system chlorinated natural rubber (CR)/Ni[P(OC6H5)3]4 was studied. The orders in monomer and in catalyst were found to be 1 and 1,5, respectively, corresponding to a free radical mechanism. In most cases, the homopolymer was extracted by an experimental technique described in Part 1 of this series. The extent of homopolymer formation increases with increasing reaction temperature and with the [Ni]/[Cl] ratio. Experimental conditions are described avoiding homopolymer formation. The graft copolymerization initiated by the system CR/Ni[P(OEt)3]4 was studied at different temperatures. At 35°C, this initiator was found to be very active, but copolymerization stops after 10% conversion.
Photoinitiation, 7. Terpolymerization of the system acrylonitrile/maleic anhydride/styrene
Authors: Capek Ignác , Bartoň Jaroslav 
Published: April 2003

AbstractThe photoinitiated (at wavelength λ = 365 nm) terpolymerization of acrylonitrile, maleic anhydride and styrene in the presence and/or absence of additives such as ZnCl2 or N,N‐dimethylaniline (DMA) in acetone was studied, and the relative reactivities R of maleic anhydride and acrylonitrile towards a styryl radical were determined. In the presence of ZnCl2 and/or DMA, the relative reactivities R are by about 40% lower than the value of R (= 13,3 ± 2,1) for the terpolymerization system without additives.
Synthèse par voie radicalaire de polymères à extrémités hydroxylées, 9. Synthèse de polybutadiènes: étude des microstructures
Authors: Brosse Jean‐Claude , Bonnier Maryvonne , Legeay Gilbert 
Published: April 2003

AbstractButadiene polymerization with hydrogen peroxide resulted in the simultaneous formation of oligomers, polymers, and high polymers. Analyses of their microstructures showed that oligomers have a higher content of 1,2‐structures (28%) than the polymers (22%). The nature of the chain ends was determined with low molecular weight compounds. The content of 1,2‐units is distinctly higher in the oligomers, which shows that initiation takes place preferably in 1,2‐ and propagation in 1,4‐position. Besides hydroxyl end groups, other functional groups were detected in small quantities in the low molecular weight products: aldehydes, ketones, acids, hydroperoxides, and epoxides. These functions result from secondary reactions such as transfer, initiation, or termination reactions with alcohol releasing radicals.
Wholly aromatic polyamides containing bridged biphenylylene groups, 2. Copolyamides
Authors: Kaneda Takaho , Ishikawa Seiji , Daimon Hiroshi , Katsura Toshio , Ueda Mashiro , Oda Kunio , Horio Masao 
Published: April 2003

AbstractA number of wholly aromatic copolyamides containing bridged biphenylylene groups were synthesized from a mixture of aromatic diamines and terephthaloyl chloride, on one hand, and from a mixture of aromatic diacid dichlorides and 1,4‐phenylenediamine, on the other hand. Each mixture of diamines and of diacid dichlorides was constituted of a phenylene derivative and a bridged biphenylylene derivative. The copolyamides synthesized were dissolved in high concentration sulfuric acid and spun into fibers. The fibers spun showed fairly high tensile strengths and high initial moduli, but annealing caused further increase in strength and modulus. All the copolyamides studied had very high thermal resistances.
Practical aspects to the use of indirect fourier transformation methods
Authors: Müller Karl , Glatter Otto 
Published: April 2003

AbstractPractical hints for the application of the indirect Fourier transformation method are given. In detail there are discussed the problems of stabilization of the least squares routine, the estimation of the maximum dimension of the particles, the choice of an appropriate number of the spline functions, the combination of scattering functions measured with different primary beam geometry, standard deviation and error propagation of the solution functions, influence of the interparticle interference effect and background scattering on the results, determination of the radius of gyration and the scattering intensity at zero angle and finally the possibility of simulation of measuring curves starting with model bodies is described. It is attempted to demonstrate the advantages of indirect Fourier transformation on hand of several practical examples.
Influence of expansion of polymer molecules in solution on non‐newtonian flow behavior
Authors: Ito Yoshio , Shiina Shoji , Tokue Ikuo 
Published: April 2003

AbstractNon‐Newtonian viscosity could be explained by the Graessely entanglement viscosity theory modified by a frictional viscosity for moderately concentrated solutions of polydimethyIsiloxanes over a range of shear rates from lower to upper‐Newtonian flow. The expansion of a polymer molecule was kept under control by use of solvents with different dissolving powers of the polymer. The result shows that only the frictional viscosity is strongly related to the degree of expansion of a polymer molecule in solution and that Graessley's plots are independent of that. Extrapolation of the frictional viscosity versus concentration curves to 100wt.‐% show a common value of 0,09 Pa·s in spite of different degrees of expansion of the polymer molecules in solution. This common value was equal to the viscosity value for melt polymer with the same molecular weight as a polymer segment. It is concluded that the frictional viscosity is caused by solvent‐solvent, solvent‐polymer segment, and segment‐segment interactions.
Aliphatic‐aromatic polyamide‐imides from diisocyanates, 2. Study of the influence of the reaction conditions on polymer structure
Authors: de la Campa José G. , de Abajo Javier , Nieto José L. 
Published: April 2003

AbstractThe polycondensation of 4,4′‐methylenediphenylisocyanate and 6‐(4‐carboxyphthalimido)‐hexanoic acid was studied under different conditions in order to establish the influence of factors such as temperature, catalyst, stoichiometric disbalance, and addition order of reactants on the molecular weight and the chemical composition of the final polyamide‐imide. All these factors proved to influence the extent of possible side reactions that lead to undersirable functions, the main ones being urea functions that locate within the polymer backbone. Other side‐reactions proposed to explain the formation of acylureas or biurets did not take place in appreciable extent since these functions could not be detected by NMR spectroscopy. Therefore, particular emphasis was made to prevent the formation of urea by changing the polycondensation conditions. A first attempt to clarify the regularity degree of the polymers (amounts of head to tail and head to head addition) by 1H NMR spectroscopy was also made.
Effect of metal laurates on polymerization of methyl methacrylate in benzene
Authors: Theerthalingam T. , Kothandaraman H. , Santappa M. 
Published: April 2003

AbstractPolymerization of methyl methacrylate initiated by laurates of Fe(III), Co(III) and Mn(III) in benzene medium at 60°C was studied. The polymerization was found to be free radical in nature. The rate of polymerization was proportional to the square of the concentration of the monomer and inversely proportional to the concentration of the solvent. The initiator exponent was found to be 0,23. The rate parameters for the system were evaluated. The reactivity of the different metal laurates was compared. A kinetic scheme is proposed in the light of the experimental results involving initiation of the polymerization by a monomer‐initiator complex and termination by a initiator‐solvent complex.
Syntheses and infrared‐spectroscopic studies of homo‐oligomeric peptides derived from γ‐benzyl‐L‐glutamate
Authors: Ozaki Takuo , Shoji Akira , Furukawa Makoto 
Published: April 2003

AbstractA series of homo‐oligomeric peptides derived fromγ‐benzyl‐L‐glutamate, Nps‐[L‐Glu‐(OBzl)] n+m−OBzl (4(n, m)) (n + m = 2 to 12, 15, 16, 18, 21, and 24), were synthesized for the first time by the DCC‐ONSu method using and activated easter. The identification and conformation of these peptides in cast films were investigated successfully by IR spectroscopy. It was found that the formation of the β‐structure begins with the tetrapeptide, and that of the α‐helix in the range from the hexapeptide to octapeptide. There is some evidence for small quantities of other conformational nuclei which may coexist as preferred conformations in peptides between the hexa‐ and decapetides. These effect cannot be attributed to sample purity since they could be shown to be analytically pure.
Etude par spectroscopie infrarouge d'alcanes ramifiés et de polymères modèles — application à la determination du taux de ramifications dans les polyéthylènes basse densité
Authors: Frêche Patrick , Grenier‐Loustalot Marie‐Florence , Cascoin Alain 
Published: April 2003

AbstractThe absorption band at 1378 cm−1 was used for the quantitative determination of branching in polyethylene. Using various models with different alkyl groups (12‐alkyltriacosanes, 11,20‐dialkyltriacontances, alkylcyclohexanes, homopolymers), new absorption coefficients, depending on their branching, were obtained. The degrees of branching of a series of copolymers deriving from α‐olefins (15 compounds) determined by infrared spectroscopy with the new coefficients and by 13C NMR spectroscopy were compared.
Induced circular dichroism of polypeptide‐dye systems in a mesophase
Authors: Sato Yukio , Hatano Masahiro 
Published: April 2003

AbstractThe interaction of polypeptides with dyes in a lyotropic mesophase, consisting of Tween 80 (monooleate of the ether of sorbitan with 4 mol of polyethyleneglycol) and water, was studied, and the arrangement of dyes in the mesophase was discussed on the basis of the spectral change of circular dichroism under an electric field. The following results were observed. (1) The addition of a polypeptide to the mesophase considerably influenced the helical pitch of the mesophase. (2) In the mesophase the complexes of polypeptides with dyes were formed more easily than in aqueous solution. (3) When this mesophase was used as an orientation solvent under the electric field, the observed variation of circular dichroism bands could be used for an assignment of each band polarization. Thus, in the acidic region, acridine orange molecules are bound in such a manner that their long‐axes of molecular plane form a right‐handed super‐helix around the core of the α‐helix of poly(α,L‐glutamic acid). In the alkaline region, the poly(α,L‐glutamic acid)‐acridine orange complex cannot take a helical form, even when the mole ratio of polypeptide residues to dye molecules is ≈ 1.
Synthesis and properties of copolyimides, 2. Preparation and properties of polypyromellitimides from p‐phenylenediamine and m‐phenylenediamine
Authors: Babu Gaddam Nana , Samant Shubha 
Published: April 2003

AbstractCopolymers were prepared by reacting a prepolymer consisting of an anhydride terminated polymeric acid from pyromellitic anhydride and a diamine (p‐ or m‐phenylenediamine), with the second diamine. The resulting polymeric acids were converted into polyimides by thermal cyclodehydration. The corresponding random copolyimides were prepared by a conventional procedure and their properties were compared with those of three step copolyimides of similar composition.