bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enzymatic cleavage of side chains of synthetic water‐soluble polymers
Authors: Drobník J. , Kopeček J. , Labský J. , Rejmanová P. , Exner J. , Saudek V. , Kálal J. 
Published: April 2003

AbstractWater‐soluble copolymers based on poly[N‐(2‐hydroxypropyl)methacrylamide] and bearing in their side chains a chromogenic substrate for chymotrypsin were prepared by direct copolymerization or polymeranalogous reaction. The substrate was L‐phenylalanine‐4′‐nitroanilide linked by its amino group to the terminal carboxylic group of the side chain. The cleavage of the substrate thus bonded, was expressed by means of the Michaelis constant, the maximum velocity, and the percentage of substrate unit accesible to the enzyme. The effect of length and chemical structure of the side chain was investigated in the first place. It was found that the chain must be longer than 6 atoms; longer chains are generally more favourable for this cleavage. The ε‐aminocaproyl group provides a chain that is most favourable for the cleavage, whereas chains with several glycyl units, though longer, are less favourable. Polymers with higher content of the substrate units undergo cleavage more readily.
Synthèse par voie radicalaire de polymères à extrémités hydroxylées, 3. Synthèse de poly(acétate de vinyle)
Authors: Pinazzi Christian , Lenain Jean‐Claude , Brosse Jean‐Claude , Legeay Gilbert 
Published: April 2003

AbstractSous l'action de la chaleur, le peroxyde d'hydrogène est scindé en radicaux hydroxyle pouvant agir comme agents d'amoràe d'un processus de polymérisation. On peut ainsi obtenir des polymères hydroxylés de petites masses moléculaires. L'adjonction d'un alcool au milieu réctionnel modifie les conditions de la polymérisation et permet de moduler les taux de conversion et les masses moléculaires moyennes en nombre. Les résultats sont différents selon que le polymère est soluble ou non dans l'alcool. La polymérisation de l'acétate de vinyle selon ce procédé, dans le méthanol solvant du polymère, fait l'objet du présent travail. La nature des polymères obtenus est déterminée: mode de distribution des masses moléculaires, microstructure, taux de groupements hydroxyle par macromolécule; l'influence de divers paramètres est éaglement étudiée: durée, température, proportions d'eau oxygénée et de solvant.
Synthèse par voie radicalaire de polymères à extrémités hydroxylées 4. Polymérisation et copolymérisation de butènes
Authors: Pinazzi Christian , Legeay Gilbert , Brosse Jean‐Claude 
Published: April 2003

AbstractL'homopolymérisation dans le méthanol des butène‐1, butène‐2 et isobutène amorcée par l'eau oxygénée conduit à la formation, avec de faibles taux de conversion, de polymères de faibles ou de très faibles masses moléculaires comportant des fonctions hydroxyles. La copolymérisation de ces éthyléniques avec un monomère diènique, tel que le butadiène, s'effectue facilement. Les constantes de réctivité ont été déterminées. Elles sont liées aux structures des monomères: le butène‐2 polymérise et copolymérise mieux que l'isobutène mais moins bien que le butène‐1.
Studies on aqueous polymerization of acrylamide, 2. Potassium persulfate/2‐mercaptoethanol redox system
Authors: Husain M. Mukhtar , Misra Sada Nand , Gupta Archana 
Published: April 2003

AbstractThe polymerization of acrylamide in aqueous media initiated by the potassium persulfate/2‐mercaptoethanol redox pair was studied at 30°C under nitrogen atmosphere. The initial rate of polymerization was found to be proportional to nearly the 1,5th power of the potassium persulfate concentration within the range of 0,6 to 2,0 mmol l−1 and to the first power of acrylamide concentration in the range of 0,1 to 0,14 mol l−1. The rate was also found to be proportional to the first power of the 2‐mercaptoethanol concentration within the range 4,0 to 8,0 mmol l−1. The overall activation energy was found to be 134 kJ mol−1.Further the effect of salts (NaCl, KCl, NH4Cl, Na2C2O4, K2C2O4·H2O, (NH4)2C2O4,MnSO4·4H2O, and NaF) and aliphatic alcohols (methanol, ethanol, and propanol) was tested.
Reaktion an Ziegler‐Natta‐Katalysatoren, 12. Anwendung der Olefin‐Metathese zum Nachweis einer radikalischen Aralkylierung von 1,4‐Polybutadien
Authors: Hummel Klaus , Demel Hans , Wewerka Dieter 
Published: April 2003

Abstract1,4‐Polybutadien wurde mit Alkylbenzolen (Toluol, Äthylbenzol, o‐, m‐ und p‐Xylol, Mesitylen) und Dicumylperoxid in einer radikalischen Reaktion partiell aralkyliert. Die erhaltenen Polymeren wurden IR‐spektroskopisch untersucht und durch Metathese mit 4‐Octen unter Verwendung eines WCl6/Sn(CH3)4‐Katalysators abgebaut. Die niedermolekularen Abbauprodukte mit Aralkylsubstituenten wurden gaschromatographisch getrennt und massenspektrometrisch identifiziert.
Über die homopolymerisation des N‐(pentachlorphenyl)maleinimids und des N‐(2,4,6‐tribromphenyl)maleinimids
Authors: Bouchal Karel , Ryska Miroslav , Hrabák František 
Published: April 2003

AbstractNew monomers with a high content of halogens, N‐(pentachlorophenyl) maleimide (1) and N‐(2,4,6‐tribromophenyl) maleimide (2) were prepared. The products of their radical polymerization consist of oligomers. Of these, products with the degree of oligomerization, n, ranging from 1–4 and from 1 to 3 were separated on a gel chromatograph for 1 and 2, respectively. Their structures were determined from the mass spectra. The elution volumes Vn of the individual oligomers were found to be a linear function of log Mn. The radical polymerization mechanism of 1 and 2 is discussed on the basis of the character of oligomers.
The copolymerization and 1,4‐cycloaddition reactions of polar vinyl monomers with butadiene in the presence of Lewis acids as catalysts
Authors: Kuran Witold , Pasynkiewicz Stanisław , Florjańczyk Zbigniew , Łyszkowska Danuta 
Published: April 2003

AbstractThe copolymerizations of acrylonitrile, methacrylonitrile, methyl acrylate, methyl methacrylate, methyl vinyl ketone, acroleine, and acrylic acid with butadiene were carried out in the presence of the Lewis acids ZnCl2, BF3, CH3AlCl2, C2H5AlCl2, AlCl3, SnCl4, and TiCl4 and also in the absence of catalyst. Relative reactivity orders of the above polar vinyl monomers in the copolymerization and 1,4‐cycloaddition reactions with butadiene and also the catalytic activity orders of Lewis acids in these reactions were determined. The composition of the polymers formed and the structure of their butadiene units were also determined. The mechanism of the copolymerization and 1,4‐cycloaddition of the polar vinyl monomers with butadiene in the presence of Lewis acids is discussed.
Infrarotspektren der koordinationsverbindungen von poly(vinylpyridin)en mit den chloriden von Rh, Ru und Pd
Authors: Roda Jan 
Published: April 2003

AbstractThe paper contains the IR‐spectra of the coordination compounds of the poly(2‐,3‐, and 4‐vinylpyridine)s with the chlorides of Ru, Pd, and Rh. The shifts of the fundamental vibrations of the pyridine ring are discussed, and the spectra are analysed. In comparison with low molecular weight analogues, the spectra are simpler, and the vibration bands are wider, which is due to the polymeric character of the ligands.
Metal complexes of alkyl substituted poly(vinylpyridine 1‐oxide)s and of poly (dimethylaminostyrene N‐oxide)s
Authors: Alshaikh‐Kadir Khalid , Holt Paul F. 
Published: April 2003

AbstractThree alkyl derivatives (3, 4, and 5) of poly[1‐(N‐oxo‐pyridyl)ethylene]s (poly(vinylpyridine 1‐oxide)s) give complexes with some or all chlorides of copper (II), zinc, mercury(II), iron(III), and cobalt(II), in which all the N‐oxide groups are coordinated with metal, the mole ratio NO/metal being 2:1. The three poly[(N‐oxo‐dimethylamino)phenylethylene]s (poly(dimethylaminostyrene N‐oxide)s) (6, 7, and 8) give complexes with copper(II), mercury(II), and iron(III) chlorides but, even when an excess of metal chloride is available, some N‐oxide groups do not coordinate with metal as shown by IR absorption data. The degree of coordination is 0,5 for complexes of 6, but it is 0,4 for the complexes of 7 and 0,33 for the complexes of 8.
Über die boronierung von polystyrol
Authors: Hartmann Manfred , Carlsohn Hartmut 
Published: April 2003

AbstractBoronic acid groups can be introduced in crosslinked and linear polystyrene by metalation with the complex butyllithium/N,N,N′,N′‐tetramethylethylenediamine and subsequent treatment with boric acid esters. Investigations of the photochemical boronation of polystyrene by boron tribromid show that the reaction is accompanied by strong chain degradation, whereas the former method leads to an increase in molecular weight.
Polar effect in free volume theory for polymer solution thermodynamics
Authors: Sugamiya Ken 
Published: April 2003

AbstractPolar effects on the thermodynamic properties of polymer solutions are treated within the framework of the free volume theory. The Sutherland potential and the dipole‐dipole interaction are assumed to represent intermolecular interaction in a polar system, with an approximation concerning the radial distribution function. Application of the treatment to some polar systems shows that the theoretical %‐parameters are smaller than the observed ones and than the calculated ones without regard to the polarity. The excess volume ratios are, however, nearer to the observed ones compared with those evaluated without the account of the polarity. Therefore, the present results are fairly good for strong polar solutions.
Thermostimulated creep and depolarization thermocurrent in low density polyethylene
Authors: Chatain Daniel , Lacabanne Colette , Monpagens Jean‐Claude 
Published: April 2003

AbstractA new method for the study of orientational movements in polymeric solids is proposed: in a mechanical step‐function experiment, we thermally stimulate the response at a constant stress. The great advantage of the thermostimulated creep (TSC) technique is to allow the experimental resolving of the mechanical retardation time spectrum. In low density polyethylene, the existence of a discrete spectrum of mechanical retardation times is demonstrated; it has the same fine structure than the spectrum of dielectric relaxation times deduced from the study of depolarization thermocurrent (DTC) on the same sample.
Asymmetric oxidation of sulfides with N‐chloro‐nylon‐6.6 in the presence of optically active alcohols
Authors: Sato Yoshiyasu , Kunieda Norio , Kinoshita Masayoshi 
Published: April 2003

AbstractTreatment of sulfides with N‐chloro‐nylon‐6.6 in the presence of water or alcohols affords the corresponding sulfoxides in good yields. 18O is incorporated in the corresponding sulfoxides by oxidation using H2 18O as oxygen source. A remarkable retardation of the oxidation is observed in the case of using alcohols with a bulky group. In the presence of optically active alcohols, the oxidation of sulfides results in the formation of optically active sulfoxides. The stereochemical route for the asymmetric oxidation is discussed.
Optically active vinyl polymers containing fluorescent groups, 2. Synthesis of optically active vinyl carbazole derivatives
Authors: Chiellini Emo , Solaro Roberto , Ledwith Anthony 
Published: April 2003

AbstractSynthesis and characterization of (S)‐3‐sec‐butyl‐9‐vinylcarbazole (7), (S)‐9‐(2‐methylbutyl)‐2‐vinylcarbazole (14), and (S)‐9‐(2‐methylbutyl)‐3‐vinylcarbazole (18) are described in detail.
13C NMR analysis of chemical inversion in polypropylene
Authors: Asakura Tetsuo , Ando Isao , Nishioka Atsuo , Doi Yoshiharu , Keii Tominaga 
Published: April 2003

AbstractSeveral new peaks observed in the 13C NMR spectra of polypropylene prepared with a VCl4/Al(C2H5)2Cl catalyst were assigned to the chemical inversion in the chain such as an isolated head‐to‐head or tail‐to‐tail unit.
Synthesis of oligomers containing several hydroxyimino groups
Authors: Yukimasa Hidefumi , Sawai Hiroaki , Obata Naruyoshi , Takizawa Takeo 
Published: April 2003

AbstractOctane‐3,6‐dione (1a) and undecane‐3,6,9‐trione (1b) were prepared by co‐oligomerization of ethylene and carbon monoxide in the presence of rhodium trioxide catalyst. C‐Nitrosation of active methylene groups of 1a and 1b with butyl nitrite or nitrosyl chloride gave products 3, 4, 6, and 7 and 10–14 containing hydroxyimino groups or isoxazole rings. The oximes 16–20 were obtained by oximation of carbonyl groups of 1a, 3, 4, 6, and 7 with hydroxylamine hydrochloride.
Reactivity ratios of ionizing monomers in aqueous solution. Copolymerization of acrylic and methacrylic acids with acrylamide
Authors: Ponratnam Surendra , Kapur Sham Lal 
Published: April 2003

AbstractThe copolymerization behaviour of the systems (a) acrylic acid (AA)‐acrylamide (AM) and (b) methacrylic acid (MA)‐acrylamide was studied in aqueous solution at 30°C as a function of pH. The copolymerization was carried out to high conversion (>10%) and the monomer reactivity ratios r1 for (AA or MA) and r2 (for AM) were computed using the Mayo‐Lewis integrated equation. For the system (a), r1 reached its maximum value of 0,92 at pH 2, and its minimum of 0,33 at pH 6, thereafter increasing again. No systematic variation was found for r2. In system (b), r1 decreased sharply from a maximum of 2,8 at pH 4 to 0,19 at pH 6, then increasing to 0,39 as the pH was raised to 10. The r2 value showed a gradual increase from 0,2 at pH 4 to 0,57 at pH 9. Addition of NaCl (conc.: 1 mol/l) partially restored the value of r1 for both AA and MA to those at low pH. The variation of r1 of AA and MA nearly parallelled the homopolymerization rates of the respective monomers, with respect to pH. These variations were traced to the electrostatic repulsive interactions between the reactive species—ionized monomer and ionized polymeric radical—and hydrophobic interactions. Certain discrepancies in the trends of r1 and r2 were also noted.
Greffage d'acides aminés possédant une troisième fonction sur un polymère, 3 Fixation de lysine aux extrémités d'un polymère α,ω‐difonctionnel. – Modèle de réaction
Authors: Guéniffey Henri , Garnier Raymonde , Pinazzi Christian 
Published: April 2003

AbstractLysine, as cupric complex, was fixed by its ε‐NH2 end group onto pentamethylene or 3‐oxapentamethylene dichloroformates, and to sebacoyl dichloride. Copper elimination yields dicarbamates and diamides which can be used as prepolymers or as crosslinking agents.
Copolymerization of carbon dioxide and some oxiranes by organoaluminium catalysts
Authors: Koinuma Hideomi , Hirai Hidefumi 
Published: April 2003

AbstractCarbon dioxide was copolymerized with methyloxirane and 7‐oxabicyclo[4.1.0]heptane using triethylaluminium as a catalyst component. Factors to control the copolymer composition were sought on the basis of an assumed copolymerization mechanism. Compared to nonpolar solvents, ethereal solvents were found to increase the carbon dioxide content in the copolymer obtained by the triethylaluminium/water system, giving a fraction with almost alternating sequence. The addition of a Lewis base, especially treiphenylphosphine, to triethylaluminium was also useful to get copolymers of high carbon dioxide content. The coincidence of these results with the expectation from the assumed copolymerization scheme clearly indicates that the copolymerization proceeds through a coordinated anionic mechanism.
Polymere ester von Säuren des phosphors, 5. Ringöffnende polymerisation des 2‐phenoxy‐1,3,2‐dioxaphospholan durch Michaelis‐Arbuzov‐reaktion
Authors: Vogt Walter , Ahmad Nasim U. 
Published: April 2003

Abstract2‐Phenoxy‐1,3,2‐dioxaphospholane (14) was polymerized by benzyl halogenides at temperatures between 120 and 200°C. It was found that the main chain consists predominantly of unexpected ethylene 1,2‐ethanediphosphonate units 7; only about 10% of the monomer was incorporated as the expected 2‐hydroxyethanephosphonate structure. An insertion mechanism, proposed by Harwood and Patel for the analogous polymerization of 2‐phenyl‐1,3,2‐dioxaphospholane, does not agree with our experimental results. A hypothesis is developed involving a two step addition process, which exclusively occurs at the chain end. Alternating, one monomer molecule is added by a normal Michaelis‐Arbuzov‐reaction, and then a second molecule is added followed by an intermediate 1,2‐shift of the endstanding halogen cryptoanion. With benzyl bromide as initiator, the growing end shows alternating the sequences CPOCCBr (2‐bromoethyl ester) and COPCCBr (2‐bromoethanephosphonate).
Die struktur kollagenähnlicher homo‐ und heteropolytripeptide, 3. Die synthese von iysinhaltigen polytri‐ und ‐hexa‐peptiden
Authors: Khodadadeh Keyumarss , Heppenheimer Kurt , Heidemann Eckhart R. 
Published: April 2003

AbstractThe syntheses and polycondensations of Nε‐Z‐L‐Lys‐Gly‐L‐Pro (5), L‐Pro‐Nε‐Z‐L‐Lys‐Gly (11), Gly‐L‐Pro‐Nε‐Z‐L‐Lys (17), Nε‐Z‐L‐Lys‐Gly‐L‐Ala (23), Nε‐Z‐L‐Lys‐Gly‐L‐Pro‐L‐Ala‐Gly‐L‐Pro (35), Gly‐L‐Glu(OBut)‐Nε‐Z‐L‐Lys‐Gly‐L‐Pro‐L‐Pro (46), and Gly‐L‐Pro‐Nε‐Z‐L‐Lys‐Gly‐L‐Pro‐L‐Pro (54), are described. The polymers were separated by gelchromatography into three fractions of different molecular weights. The polymers of 5 and 35 cannot be redissolved after lyophilization.
Influence of the nature of the solvent on the lamellar crystalline structure of block copolymers with an amorphous block and a crystallizable poly(ethylene oxide) block
Authors: Gervais Monique , Gallot Bernard 
Published: April 2003

AbstractBlock copolymers of styrene and ethylene oxide, (SEO), and of butadiene and ethylene oxide, (BEO), in the presence of a preferential solvent of the amorphous block exhibit always a lamellar structure (LC) with crystallized and folded poly(ethylene oxide) chains at temperatures below about 50°C.To precise the influence of the nature of the solvent on the refolding of the poly(ethylene oxide) chains (PEO), we have studied by X‐ray diffraction and differential scanning calorimetry the LC structure of the copolymers BEO and SEO in the presence of different solvents for the amorphous block. The copolymers SEO were studied in the presence of xylene, toluene and diethyl phthalate. Diethyl phthalate being a bad solvent for polybutadiene, the copolymers BEO were studied only in the solvents xylene and toluene.The influence of the nature of the solvent on the extent of the domain where the LC structure exists, on the refolding, and on the crystallinity of the poly(ethylene oxide) blocks is demonstrated.
Zur entschmierung der röntgenkleinwinkelstreukurven von hochpolymeren
Authors: Schollmeyer Eckhard , Tschang Chung‐Ji , Hirt Peter , Herlinger Heinz 
Published: April 2003

AbstractA method for slit‐hight corrections is described, in which the experimental X‐ray small angle scattering curve is represented by a cubic spline function. This method is applied on the theoretical scattering curve of spherical particles with homogenious electron‐density and on scattering curves of poly(hexamethylene adipate).
On the kinetics of the polymerization of some ammonium methacrylates with different alkyl chain lengths in aqueous solution
Authors: Ringsdorf Helmut , Thunig Dieter 
Published: April 2003

AbstractMethacryloyloxyalkyltrimethylammonium chlorides (1a–c) with different alkyl chain lengths were synthesized and polymerized radically with 4,4′‐azobis(4‐cyanovalerianic acid) and K2S2O8 as initiators. With K2S2O8 as initiator, reaction orders of 0,5 and 1 with respect to initiator and monomer, were found. For the ionic monomers with longer alkyl chains the ratio of rate constants kp(2fkd/kt)0,5 was determined over a wide concentration range. It was found that with decreasing monomer concentration the ratio of rate constants increases, which is caused by a diminished termination rate because of an increased electrostatic repulsion of the ionic polymer radicals in dilute solution (increase of dissociation). Methacryloyloxyethyltrimethylammonium chloride (1a) doesn't show this effect. This can be explained by the diminished effective charge of the ammonium group in the preferred gauche conformation of the molecule.
Esterification of benzenecarboxylic acids with ethylene glycol, 11. Kinetics of the initial stage of metal‐ion catalyzed polyesterification of isophthalic acid with ethylene glycol
Authors: Nondek Lubomír , Málek Jaroslav 
Published: April 2003

AbstractThe kinetics of the reaction of isophthalic acid (4) with excess of ethylene glycol (5) in the presence of metal compounds as catalysts was determined in an open system and at 171–193°C by using liquid chromatography on silica gel. At an initial mole ratio of 5/4 equal to or higher than 20, the initial stage of metal‐ion catalyzed polyesterification is characterized by the absence of oligomers and involves two consecutive and two concurrent reactions, i.e., metal‐ion catalyzed and parallel uncatalyzed esterification of 4 to 2‐hydroxyethyl hydrogen isophthalate (6) and metal‐ion catalyzed and parallel uncatalyzed esterification of 6 to bis(2‐hydroxyethyl) isophthalate (7). The rate constants for all the individual reaction steps were determined. The metal‐ion catalyzed conversion of 4 to 6 (reaction (i)) is first‐order in 4 and that of 6 to 7 (reaction (ii)) is half‐order in 6; both reactions (i)–(ii) catalyzed by tin(II) oxalate are first‐order in tin(II) ions. These kinetic relations hold through at least 97% of transformation of 4 into 7. The activity of metal ions in the catalyzed esterification reactions (i)–(ii) decreases in the order Sn2+>Ti4+ ≫ Zn2+ > Pb2+ ≈ Co2+≈ Cd2+. The activation energies Ei(Sn) and Eii(Sn) for the tin(II)‐ion catalyzed reactions (i)–(ii) are 85,1±4,9 kJ mol−1 and 83,1±4,2 kJ mol−1, respectively, and the corresponding activation entropies ΔS and ΔS are −;134,1±11,0 J K−1 mol−1 and −148,6±9,5 J K−1 mol−1, respectively.
Untersuchungen zur kinetik der polykondensation von sebacoylchlorid mit α,ω‐alkandiolen
Authors: Ueberreiter Kurt , Engel Michael 
Published: April 2003

AbstractThe kinetics of polycondensation of sebacoyl chloride with α,ω‐alkane dioles HO—(CH2)n—OH (5⩽n⩽10) in dioxane can be described by a second order law related to the functional groups. The rate constants at a given temperature have all the same value within the accuracy of the measurements. The mean values of the rate constants are k=0,63·10−3mol−1ls−1 (T=299,9 K),k=1,19·10−3mol−1ls−1 (T=312,9 K), and k=2,98·10−3mol−1l s−1 (T=331,8 K). Thus, these polycondensation reactions are independent of the chain length of the α,ω‐dioles. The mean activation energy is EA=41 kJ mol−1 and the pre‐exponential factor is A=8,5·10×3 mol−1ls−1.
Polyelectrolyte complexes of sodium dextran sulfate with chitosan, 2
Authors: Fukuda Hiroshi , Kikuchi Yasuo 
Published: April 2003

AbstractSolutions of sodium dextran sulfate and chitosan were co‐reacted under various experimental conditions to form a water‐insoluble hydrous precipitate. The mole ratios of N/S in the polyelectrolyte complexes were estimated to be 0,79 to 2,54 depending on pH as well as on the mixing ratio of the complexing components. IR spectroscopic studies, blood test, elementary analyses, color reactions with toluidine blue, and the studies on solubility revealed that two polyelectrolyte complexes, different in molecular structure, were formed: series A and B (Tab. 1), where the latter emerged at lower pH condition. It seems that the number of binding sites between NH and OSO in B series is smaller than that in A series, considering their nitrogen content or the formation of OSO3H groups in B series. Furthermore, the polyelectrolyte complexes of A series rather suppressed the coagulation of blood, whereas those of B series enhanced it. The mechanism is still not completely elucidated. Nonetheless, the experimental results appear to open an important reservoir of anti‐thrombogenetic materials whose properties may be tailored.