bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reactive polymers, 22 Hydrolysis of schiff's bases and of hydrazones bonded on a crosslinked copolymer
Authors: Zacharieva Ekaterina I. , Mikeš František , Žůrková Eva , Kálal Jaroslav 
Published: April 2003

AbstractThe hydrolysis of Schiff's bases and hydrazones prepared by reactions of methylamine, ethylenediamine, butylamine, tert‐butylamine, sec‐butylamine, isobutylamine, octylamine, benzylamine, and isonicotino‐hydrazide with free aldehyde groups of the crosslinked macroporous copolymer divinylbenzene‐methacryl‐aldehyde, was investigated. The highest initial rate of hydrolysis was observed in the range of a high proton concentration. The initial hydrolysis rate increases and the conversion of the hydrolysis reaction decreases with increasing basicity of the amines. Comparison with the corresponding low‐molecular‐weight Schiff's bases indicated considerable polymer effects on the hydrolysis reaction.
Die orientierung der kristallinen und der nichtkristallinen bereiche in verstreckten polyethylenterephthalat‐folien
Authors: Biangardi Harald J. 
Published: April 2003

AbstractFilms of poly(ethylene terephthalate) were stretched at 100°C with different stretching rates. By this, oriented films with birefringences between 3.10−3 and 100.10−3 were produced. After a crystallization with fixed ends at 150°C, 200°C and 240°C, the orientation function of the crystalline regions, the density, and the birefringence were measured. From this data, the orientation function of the noncrystalline regions was computed. The results obtained show, that only a qualitative but not a quantitative computation of the orientation function is possible. With increasing birefringence of the material before crystallization, the orientation of the crystalline and the noncrystalline regions increases. Up to birefringences of Δn0=40.10−3 in both regions a strong increase of the orientation function is observed. At higher birefringences Δn0, the increase diminishes and depends strongly on the crystallization temperature. The orientation of the crystals after crystallization is better than the initial average orientation of the sample before crystallization. Further the orientation function of former reported structure models for the crystalline regions were computed in dependence of the structure parameters. Comparing the computed and experimental results one finds, that the change from structures consisting of twisted lamellae into such of bended lamellae occurs at a birefringence Δn0=20.10−3.
13C NMR sequence analysis, 17. Investigation on polyesters from diacids and diols
Authors: Kricheldorf Hans R. 
Published: April 2003

AbstractNumerous polyesters were prepared from 1,2‐ethanediol, 1,3‐propanediol, 1,4‐butanediol, 1,6‐hexanediol, 1,12‐dodecanediol, 1,4‐phenylenedimethanol, and hydroquinone on the one hand and succinyl chloride, glutaroyl chloride, adipoyl chloride, suberoyl chloride, sebacoyl chloride, isophthaloyl chloride, and tetephthalolyl chloride on the other hand. The 13C NMR spectra of all polyesters were measured in trifluoroacetic acid and relationships between the structure of the monomeric units and the chemical shifts of the carbonyl and OCH2‐signals were established. Copolyesters were prepared either by cocondensation of two diacid dichlorides and two diols or by thermal transesterification of two homopolyesters. The 13C NMR spectra allow one to distinguish copolyesters from mixtures of corresponding homopolyesters and they allow the determination of the length of homogeneous blocks.
Ethylene‐butadiene copolymers, 1. Preparation with modified vanadium catalysts
Authors: Bruzzone Mario , Carbonaro Antonio , Corno Carlo 
Published: April 2003

AbstractThe copolymerization of ethylene with 1,3‐butadiene to give crystalline, homopolymer‐free, high molecular weight, substantially linear copolymer is described. Butadiene polimerizes almost exclusively in a trans‐1,4 structure, ranging in content from zero to 50 mole‐%. At relatively low content of butadiene monomeric units (≤30 mole‐%) X‐ray crystallinity is of polyethylene type with a slight variation of the structural parameters. At higher levels of butadiene monomeric units, crystallinity of trans‐1,4‐polybutadiene is also observed. The products with little unsaturation (1–5 mole‐%) melt at about 132°C and are able to crosslink with sulfur‐based recipes. A 13C NMR study shows a block‐type structure, but the copolymer appears homogeneous in composition. The product of the reactivity ratios was evaluated. The catalyst system consists of vanadium tris(acetylacetonate), diethylaluminium chloride, and an acidic compound or its precursor. The nature and the amount of the acidic modifier regulate the polymerization rate as well as the molecular weight, composition, and long branching of the copolymer, so that a strict control of the catalyst system is required. The behaviour of the catalyst is tentatively explained by the polarity of the active carbon‐vanadium bond, which depends on substituents and complexing agents.
Ethylene‐butadiene copolymers, 2. Long branching, double bond distribution and their effect on polymer properties
Authors: Bruzzone Mario , Giuliani Giampaolo , Paiella Roberto 
Published: April 2003

AbstractThe principal structural characteristics of ethylene‐butadiene copolymers prepared with a modified vanadium catalyst are described. The distribution of the butadiene monomeric units, though non‐random, is sufficiently homogeneous at low monomeric units content of butadiene (1–3 mole‐%) that a ready and efficient vulcanization with sulfur based systems is easily achieved.Long chain branching, which has a detrimental effect on the copolymer properties, can be measured rheologically and controlled at a very low level by the catalyst system. Vulcanized ethylene‐butadiene copolymers show improved mechanical properties with respect to high density polyethylene and good processability before curing.
Polypeptides containing adenine and uracil residues
Authors: Draminski Marcin , Pitha Josef 
Published: April 2003

AbstractAmino acids containing uracil, adenine and imidazole residues were prepared and polymerized by reacting with phosgene in ethylene carbonate. The polymers did not have a simple polypeptidic structure but were soluble in aqueous dimethylformamide and interacted with complementary polynucleotides. Alternative polymerization of amino acids by N,N′‐carbonyldiimidazole in aqueous neutral buffers proceeded with very low conversion but pure polypeptides resulted from the reaction. The following amino acids were prepared: β‐adenin‐9‐yl‐α‐alanine (1a), N‐methyl‐β‐(adenin‐9‐yl)‐α‐alanine (1b), β‐(uracil‐1‐yl)‐α‐alanine, (2a), N‐methyl‐β‐(uracil‐1‐yl)‐α‐alanine (2b), β‐(5,6‐trimethyleneuracil‐1‐yl)‐α‐alanine (3), and β‐(imidazol‐1‐yl)‐α‐alanine.
Etude cinétique de la dégradation du poly(oxytétraméthylèneoxytéréphtaloyle)
Authors: Devaux Jaques , Godard Pierre , Mercier Jean‐Pierre 
Published: April 2003

AbstractThe kinetics of thermal degradation of poly(oxytetramethyleneoxyterephthaloyl) was studied. This polyester undergoes a pyrolysis reaction in the temperature range of processing via a statistical mechanism proceeding by a random scission of the carbon‐oxygen bondings. This phenomenon is characterized by an energy of activation of 189,2kJ/mol (45,2kcal·mol−1) and by a negative entropy of activation [−20,3J·mol−1·K−1 (−4,84cal·mol−1·K−1)]. Like most of the esters with a hydrogen atom in β position, this polyester undergoes degradation by an intramolecular mechanism involving the formation of a cyclic transition state. The very high value of the degradation constant of this polycondensate is probably a result of the presence, in this chain, of the very flexible tetramethylene segment.
Syntheses and properties of polysaccharide‐type polymers, 2. Poly(cis‐3,4‐dihydroxytetrahydropyran‐6,2‐dihyloxymethylene)
Authors: Komada Hajime , Okada Masahiko , Sumitomo Hiroshi 
Published: April 2003

AbstractPoly(cis‐3,4‐dihydroxytetrahydropyran‐6,2‐diyloxymethylene) (5a), a new polysaccharide‐type polymer having the same backbone structure as that of natural dextran but differing in the number and configuration of hydroxylic groups in the repeating unit, was successfully prepared by osmium tetroxide oxidation of poly(5,6‐dihydro‐2H‐pyran‐6,2‐diyloxymethylene) under mild conditions. The structure of 5a was established from 1H and 13C NMR analyses of 5a and its methylated product 5b. Water absorption of 5a was measured at different humidities ranging from 43 to 97% at 20°C and compared with those of relevant polymers having analogous structures. The polymer 5a was found to be degraded microbiologically.
Molecular weight dependence of magnetic circular dichroism for polystyrenes in solution
Authors: Ishii Tadahiro , Utena Yoshio , Handa Takashi 
Published: April 2003

AbstractThe molecular weight dependence of the magnetic circular dichroism (MCD) for polystyrenes (PS) has been studied in various solvents by using the normalized dipole‐strength D*. The normalized MCD intensity B* is not so much affected by the molecular weight as the normalized dipole strength D+. The ratio of the Faraday parameter to the dipole strength, B*/D*, decreases as the molecular weight increases to 4,0.103 and is constant above it. The increase of the normalized D* with the increase of molecular weight is interpreted in terms of the closer approach of chromophores. These results indicate that MCD for polystyrenes is influenced by the interaction of chromophores in a polymer chain: the decrease of B*/D* comes from the increase of the interaction of chromophores. This tendency is enhanced by solvent effects on MCD.
Effect of a polymeric ligand on the formation of some cobalt(III) and copper(II) complexes with partially quarternized poly(4‐vinylpyridine)
Authors: Kurimura Yoshimi , Wakayama Katsuhiko , Nishikawa Hiroshi , Tsuchida Eishun 
Published: April 2003

AbstractIt was found that the formation constants (K) of CuX(QPVP)n− (X = ethylenediaminetetraacetate ion (edta) and N‐(2‐hydroxyethyl)ethylenediamine‐N,N′,N′,‐triacetate ion (hedta), QPVP = partially quarternized poly(4‐vinylpyridine)) increase sharply with increasing degree of quarternization (Q) of QPVP. In the Cu(edta)2−/QPVP system. K values are 481.mol−1 for Q = 0%, 8701.mol−1, for Q = 25%, and 1,1.103l.mol−1 for Q = 61%, in aqueous methanol (volume ratio 1:1) at μ = 0,1 mol.l−1, pH = 8,0. and T = 25°C. In the system CH3Co(dmg)2H2O/QPVP, K decreases linearly with increasing degree of quarternization of QPVP from K = 1,7.103l.mol−1 for Q = 0% to K = 95l.mol−1 for Q = 61% in aqueous methanol (volume ratio 3:7) at μ = 0,05, pH = 8,0, and T = 25°C. The decrease in K is +scribed to a relatively large decrease in the rate constant of the forward reaction and a small increase in that of the backward reaction.
Effect of the heteroatom x in the catalytic system ZnR2/o‐ or m‐HXC6H4XH on the copolymerization of carbon dioxide with propylene oxide
Authors: Kuran Witold , Rokicki Andrzej , Wilińska Elžbieta 
Published: April 2003

AbstractA series of new catalytic systems ZnEt2/cocatalyst were prepared and their activity in the alternating copolymerization of carbon dioxide with propylene oxide was studied. The systems ZnEt2/m‐HXC6H4XH (mole ratio 1:1) system (X = NH, S) were chosen to elucidate the influence of the heteroatom on the activity of the catalytic system. The obtained results were discussed in terms of the influence of the basicity of the heteroatom and of its hybridization on the structure and association of the catalyst molecule.
Effects of some carcinogens on conformation of histones
Authors: Su Ying‐Yet Thomas , Jirgensons Bruno 
Published: April 2003

AbstractConformational transitions of histones F1 (H1), F2a (H2A), F2b (H2B), and F3 (H3) in the presence of carcinogens 4‐nitroquinoline‐N‐oxide, 13‐H‐dibenzo[c,j]carbazole, and 7‐H‐dibenzo[c,q]carbazole were studied by the circular dichroism (CD) probe. The polypeptide main chain conformation of the very lysine rich histone F1 was not affected by these carcinogens, but the tertiary structure was modified slightly by the carbazoles. The secondary structure of histone F2a was significantly modified by the carbazoles which enhanced the helix content, whereas the effect of the 4‐nitroquinoline‐N‐oxide on the backbone conformation was weak. The tertiary structure of F2a was affected by all three carcinogens, whereby the 7‐H‐dibenzo[c,g]carbazole produced the strongest enhancement of the CD bands assigned to tyrosine and phenylalanine chromophores. Moreover, this carcinogen produced extrinsic Cotton effects in the 300–380nm spectral zone. Similar effects of the carbazoles were observed with histone F2b, although in this case the main chain conformation was changed only slightly. The secondary structure of histone F3 was slightly affected by the carcinogens but the tertiary structure was significantly modified by the carbazoles. The CD bands of F3 which were assigned to the tyrosine and phenylalanine chromophores were most strongly enhanced by the 13‐H‐dibenzo[c,j]carbazole.
Synthesis of polyamides from diamines and dinitriles with basic catalysts
Authors: Ree Keiu , Tanabe Kenji , Minoura Yuji 
Published: April 2003

AbstractThe reaction of a nitrile (acetonitrile) with a metalated amine (aniline and benzylamine) was attempted, in order to obtain the corresponding amide via hydrolysis of the amidine. This reaction was also applied for the preparation of polyamides, using diamines and dinitriles. The reaction of aliphatic diamines with aliphatic dinitriles yielded 20–30% of polyamides of low degrees of polymerization.
Chemische synthese verzweigter Polysaccharide, 8. Vergleichende struckturuntersuchungen an amylose‐ und Cellulosederivaten mit verschiedenen Substituenten an C‐6 durch optische Rotationsdispersion und circular‐dichroismus
Authors: Pfannemüller Beate , Berg Annette 
Published: April 2003

AbstractCarbanilated and tritylated derivatives of amylose and cellulose previously studied by light scattering were further characterized by measurement of optical rotatory dispersion (ORD) and circular dichroism (CD). No anomalous ORD and only a weak CD was found for 6‐tritylamylose in 1,4‐dioxane, indicating a widely unordered structure which is in accordance with the low viscosity of the compound. In comparison with the other carbanilated derivatives having substituents in C‐6 position, i.e. trityl‐, carbanilyl‐ or glucosyl groups, 2,3‐dicarbanilylamylose is distinguished by an especially high Cotton effect. This result suggests a helical chain,— clearly visible by excition splitting—, that may adopt a more regular orientation in case of free C‐6 hydroxyl groups, whereas trityl‐, carbanilyl‐, and glucosyl groups almost equally will contribute to a lower state of orientation. Conversely in the cellulose derivatives a clear steric dependence on the size of the C‐6 substituent was found. The increase of the Cotton effect observed for the bulky trityl group may arise from the β(1 → 4) linkage that causes an alternating or syndiotactic like structure in cellulose, which is more sensitive to restrictions of the free rotation due to steric effect. In addition, viscosity and optical rotation in NMP and 1,4‐dioxane were measured in the range of 20 to 70°C. An unusual behaviour is observed for 6‐trityl‐2,3‐dicarbanilylamylose in NMP indicating a conformation transition near 45°C, and is discussed in connection with the findings from light scattering measurements.
Synthesis of polyamides from esteramide‐diamines
Authors: Chau Nguyen , Matsuda Shoko , Iwakura Yoshio 
Published: April 2003

AbstractDiamines containing ester and amide linkages were obtained by the addition reaction of p‐aminobenzoic acid with arylenebis(2‐oxazolines) in N,N‐dimethylformamide. These diamines were subjected to polycondensation with various diacid dichlorides to obtain polyamides containing regular ester and amide sequences in the polymer chain.
Laser flash photolysis of poly(p‐vinylbenzophenone) in solution. Intramolecular triplet deactivation processes
Authors: Schnabel Wolfram 
Published: April 2003

AbstractPoly(p‐vinylbenzophenone) (poly[1‐(4‐benzoylphenyl)ethylene], PVBP) and p‐isopropylbenzophenone (IPB) were irradiated in benzene solution at room temperature with 347, 1 nm laser flashes (duration 25 ns). Triplet‐triplet spectra were recorded at the end of the flash. Upon following the decay of the T‐T spectra a pronounced polymer effect was found: the decay followed 2nd order kinetics in the case of the polymer and 1st order kinetics in the case of the model compound. The halflife times differ by a factor of about five (τ1/2(PVBP) < τ1/2(IPB)). Whereas τ1/2(IPB) was not influenced, τ1/2(PVBP) decreased with increasing absorbed dose per flash. From the results it is inferred that at relatively high dose rates PVBP triplets decay essentially via intramolecular T‐T annihilation and at lower dose rates via intramolecular selfquenching processes. At comparable conditions IPB triplets were essentially deactivated via interactions with solvent molecules.
Interaction between poly(L‐lysine) and sulfated poly(vinyl alcohol)
Authors: Cho Chong‐Su , Kōmoto Tadashi , Nakagami Akira , Kawai Tohru 
Published: April 2003

AbstractIonic polymer‐polymer interaction was studied in aqueous solution for poly(L‐lysine) (PLL) and sulfated poly(vinyl alcohol) (PVS) as functions of pH, the degree of sulfation, the functional unit mole ratio of the two polymers and temperature by means of circular dichroism and viscosity measurements. In all the cases studied, strong inter‐polymer complexes were formed at the functional unit mole ratio (VS)/(LL) higher than 1. Although PLL itself is well known to take the α‐helical conformation at such a high pH as 11, the PLL conformation in the PLL/PVS complexes did not depend on pH but on the degree of sulfation: at room temperature, PLL took random coil conformation in PLL/PVS‐25 (25: degree of sulfation in mole‐%) and PLL/PVS‐30, and the α‐helical conformation (helicity of 70%) in PLL/PVS‐46 and PLL/PVS‐95. Models for the complex structures are postulated. Methanesulfonic acid did not influence the conformational transition of PLL, supporting that a polymer effect took place in the complex formation between PLL and PVS. Thermal effect on the PLL conformation in the complex is also discussed.
The 13C NMR spectra of ring‐opened copolymers of cyclopentene and norbornene; reactivity ratios
Authors: Ivin Kenneth J. , O'Donnell James H. , Rooney John J. , Stewart Cecil D. 
Published: April 2003

AbstractRing‐opened copolymers of cyclopentene (M1) and norbornene (M2) were prepared by WCl6/(C6H5)4Sn initiation in chlorobenzene and analysed by 13C NMR spectroscopy. At low conversion and for feed composition in the range f1 = 0–0,7 the copolymerization behaviour is ideal, with r1 = 1/r2 = 0,44; at high conversion the copolymer tends to contain more than the ideal proportion of M2 units. For copolymers in the composition range F1 = 0–0,5 the dyad distribution is random but for F1 > 0,6 there is a tendency to blockiness. The fraction of double bonds having cis structure is 0,5–0,6 for M2M2, 0,4–0,6 for M1M2, and 0,4–0,7 for M1M1 dyads. The pair sequence of cis and trans double bonds is somewhat blocky for both M2M2M and M1M2M triads (M = M1 or M2). The chemical shifts of the central non‐olefinic carbons in both M1 and M2 units (C5 and C3) show sensitivity to triad structure provided at least one adjacent double bond is cis. This unusual ϵ‐substitution effect is interpreted in terms of conformational restrictions about certain of the main‐chain bonds when an adjacent double bond is cis. WCl6/(CH2CHCH2)4Sn initiation gives a copolymer containing practically no M1 units.
Modification au deuxième degré de polymères époxydés, 1. Etude sur molécules modèles des polyalcadiènes
Authors: Brosse Jean‐Claude , Soutif Jean‐Claude , Pinazzi Christian 
Published: April 2003

AbstractThe addition of benzoic acid to the oxirane ring of model compounds for epoxidized polymers of dienes was studied. A convenient reaction rate was observed for temperatures of about 100°C. It was found that the addition reaction can be catalysed by basic compounds. Kinetic studies showed the influence of solvent nature, of concentration of reagents, of catalysts, and of the epoxide structure. The reactivities of various acids showing particular properties (drugs, UV‐absorbers, herbicides) were investigated.
Crosslinking statistics, 1. Relation between molecular‐size distribution and partial conversion degrees expressed by equability criterion
Authors: Luby P. , Kuniak Ľ. 
Published: April 2003

AbstractOne‐to‐one correspondent relationships between the link distribution and the molecular‐size distribution for a polymer formed by a trifunctional homopolymerization of a single kind of repeating unit R(X1X2X3) are derived, where X1, X2, X3 denote functional groups of unequal reactivity. These equations make it possible to evaluate the relative reactivities of functional groups by means of partial conversion degrees α1, α2, α3 at any stage of reaction of the average conversion degree. The values of the three weight fractions of mono‐, di‐ and trimers are required as entering data, and these are the necessary and sufficient condition for a complete description of the relative reactivities. The present mathematical model is based on the condition that substitution effect and ring formation are negligible.
Cationic polymerization of cyclic thioacetals by triethyloxonium tetrafluoroborate
Authors: Kawakami Yuhsuke , Mizutani Yutaka , Yamashita Yuya 
Published: April 2003

AbstractPolymerization of 1‐oxa‐3‐thiacyclopentane with catalytic amounts of triethyloxonium tetrafluoroborate was studied. The initiation reaction was a fast and quantitative formation of ethylsulfonium salt of monomer. The propagation reaction was a slow and quite complex reaction with sulfonium transfer reactions. The reaction mechanism is discussed.
One and two component hydrogels, 3. Deswelling and compression measurements on one component hydrogels
Authors: Good William R. , Cantow Hans‐Joachim 
Published: April 2003

AbstractThe value of the Flory‐Huggins interaction parameter for water and poly(N‐vinyl‐2‐pyrrolidone)Systematic nomenclature: Poly[l‐(2‐oxo‐l‐pyrrolidinyl)ethylene].
(PVP), networks is determined by combining uni‐directional compression measurements in the swollen state with network deswelling measurements. It was found that the dependance of the parameter on crosslink density can be explained by considering the interaction of water with the crosslinking molecule, a very water insoluble compound. Moreover, it was found that the interaction parameter within the swelling range studied is independant of network concentration. The number of elastically effective network chains is overestimated by a substantial margin.
The anionic polymerization of styrene under pressure
Authors: Bunge M. , Höcker H. , Schulz G. V. 
Published: April 2003

AbstractThe kinetics of the anionic polymerization of styrene were investigated under pressure (1≤p/bar < 1800) with Na+ as counter ion in tetrahydropyran (THP) as solvent and with Cs+ as counter ion in 1,2‐dimethoxyethane (DME) as solvent. The results yielded the activation volume of the contact ion pair ΔV and the sum (ΔV + ΔVcs) of the activation volume of the solvent separated ion pair ΔV and the volume change upon formation of solvent separated ion pairs from contact ion pairs ΔVcs. The numerical values are negative. The activation volume of the solvent separated ion pairs could be estimated.
Poly(9,10‐anthrylen)e
Authors: Hinterhofer Otto 
Published: April 2003

AbstractBased on a previous work the polymerization mechanism of anthracene was studied and it was found that the initial reaction step is represented by the formation of a radical ion. Poly(9,10‐anthrylene) was prepared in order to study the relevant properties with respect to its technological applicability. Pure poly(9,10‐anthrylene)s even of relatively low molecular weight (about 3 000) are infusable and nearly insoluble. Poly(9,10‐anthrylene)s show good photoconduction.