bluuebunny/crossref_metadata_2025_split huggingface dataset:
Copolymere aus methacrylsäure und dimethacryloylimid und die abhängigkeit ihrer NMR‐spektren vom neutralisationsgrad
Authors: Ziegenberg Klaus , Klesper Ernst 
Published: April 2003

AbstractThe chemical structure of syndiotactic methacrylic acid‐dimethacryloylimide (MAA‐MAI) copolymers is studied by the NMR‐spectra of products obtained by polymeranalogous reactions and from MAA‐MAI copolymers prepared according to a different route. The kinetics of formation of the imide rings is compared with kinetic equations, confirming thereby the random formation of rings along the chain. 13C NMR spectra of MAA‐MAI copolymers depend on the degree of neutralization, α, in aqueous solution and show large changes for the carbonyl resonance region. Resolution into triads is found in organic solvents, whereas in aqueous solutions there is splitting into pentads on going from α = 0 to α = 1. The pentad assignment is made by observing the movement of the peaks with changing α and by comparison with pentad probabilities derived by a Monte‐Carlo simulation. The great changes in the chemical shift are caused to a large extent by a change in the charge of the carboxyl groups. Discontinuous changes in charge, conformation, and solvation are not found.
Kinetics of the bromination of phenols and oligonuclear phenolic compounds, 6. Far reaching effects via chains of intramolecular hydrogen bonds
Authors: Böhmer Volker , Beismann Klaus , Stotz Diethard , Niemann Wilhelm , Vogt Walter 
Published: April 2003

AbstractThe kinetics of the electrophilic bromination of 17 oligonuclear phenolic compounds with molecular bromine in acetic acid were studied at 22°C. Some of these compounds, consisting of up to 6 phenolic units, which are linked in ortho‐position by methylene bridges, and having only one (or two) reactive ortho‐position(s) at the end of the molecule, were synthesized for the first time. It could be shown, even for hexanuclear compounds, that the variation of substituents at one end of the molecule leads to a change in the reactivity at the other end, that means over a distance of 22 nonconjugated covalent links. So far, this can be explained only by a chain of intramolecular hydrogen bonds between the phenolic hydroxyl groups of adjacent phenolic units. If this chain is interrupted by one methoxy group, a substituent effect cannot be transferred in the same way.
Specific functionalization of polyoxirane by amino, carboxyl, sulfo, and halogeno end groups
Authors: Sépulchre Maurice , Paulus Gérard , Jérôme Robert 
Published: April 2003

AbstractPolyoxiranes with amino, carboxyl, or halogeno end groups were prepared by polymerization of oxirane with either anionic initiators substituted with functional or protected functional groups, or by reaction of functional deactivating reagents with anionically prepared polyoxiranes. For the protection of primary amino groups they were transformed into the corresponding cyclic imido derivatives. The deactivation of polyoxirane with potassium oxido end groups by bis(halogenomethyl)benzenes was studied with the three isomers.
Wide‐angle X‐ray scattering for swollen and glassy poly(2‐hydroxyethyl methacrylate)
Authors: Mitchell Geoffrey R. , Brown David J. , Windle Alan H. 
Published: April 2003

AbstractThe wide angle X‐ray scattering from glassy poly(2‐hydroxyethyl methacrylate) (1) is presented together with that obtained from oriented and swollen samples. The scattering is compared with that previously reported for poly(methyl methacrylate) (PMMA) and the structure discussed in relation to this polymer. The chain conformation is similar to that of PMMA, although some measure of molecular interlocking appears to reduce the main interchain peak while correlated regions of inaccessible free volume between the substantial side groups are held responsible for the main peak at s = 1,25 Å−1.
Synthesis of silicone graft polymers and a study of their surface active properties
Authors: Kawakami Yuhsuke , Murthy Ramaswamy Aswatha Narayana , Yamashita Yuya 
Published: April 2003

AbstractSilicone macromers 5, having a methacryloyl group at one end, and controiled molecular weights, were prepared by anionic polymerization of hexamethylcyclotrisiloxane (2) and subsequent termination with chlorosilane compounds containing a polymerizable vinyl groups. Graft polymers with siloxane grafts were prepared by copolymerization of these macromers with methyl methacrylate (MMA) or styrene. The surface active properties of MMA‐based graft polymers were investigated by studying the extent of surface modification of films of graft polymer‐poly(methyl methacrylate) blends.
Untersuchungen zur klärung der sensibiliserten photodegradation von polystyrol in lösungen, 1. Experimentelle befunde zum kettenabbau
Authors: Woliński Leszek , Turzyński Zbigniew , Witkowski Konrad , Zaleska Wiestawa 
Published: April 2003

AbstractPolystyrene (mass average molar mass M̄ = 609700 g/mol; molecular non‐uniformity M̄/M̄ − 1 = 0,55) solutions in 8 different solvents were irradiated by light of a mercury lamp (wavelength λ ≥ 270 nm). The rate of photodegradation of the polymer (as determiened from ΔM̄w measurements by light scattering) is strongly solvent‐dependent and only slightly dependent on the O2 concentration in the irradiated solutions. An attempt to interpret this „sensibilized”︁ photodegradation will be given in the second part of this series.
Polymers containing enzymatically degradable bonds, 9. Chymotrypsm catalyzed hydrolysis of a p‐nitroanilide drug model, p bound via oligopeptides onto poly(vinylpyrrolidone‐co‐maleic anhydride)
Authors: Pató János , Azori Mária , Ulbrich Karel , Kopeček Jindřich 
Published: April 2003

AbstractCopolymers of 1‐vinyl‐2‐pyrrolidone with maleic anhydride which contain oligopeptide sidechains with l‐phenylalanine p‐nitroanilide (Phe‐NAp) end groups were synthesized. The chymotrypsin catalyzed hydrolysis of these polymers was studied. The rate of p‐nitroaniline release was found to depend on the structure of the oligopeptied sequences: GlyGlyValPheNAp > GlyValPheNAp > GlyGlyPheNAp. From a comparison with similar substrates based on poly[N‐(2‐hydroxypropyl)methacrylamide] the influence of the structure of the polymeric backbone on the rate of cleavage of bonds at the ends of oligopeptide side‐chains was estimated.
The role of the termination by the polymer chain in the cationic polymerization of oxetane and 3,3‐dimethyloxetane
Authors: Bello Antonio , Pérez Ernesto , Fatou José Ma Gómez 
Published: April 2003

AbstractThe ring opening polymerization of oxetane and 3,3‐dimethyloxetane was carried out in dichloromethane at 25°C with triethyloxonium hexafluoroantimonate as catalyst. After polymerization, the flow times were measured for active and terminated solutions in high vacuum. In the case of oxetane, the data support the presence of branched structures in the active solutions formed by an intermolecular chain transfer reaction to the polymer chains, to give non‐strained oxonium‐ions. This intermolecular side reaction was not detected in the case of 3,3‐dimethyloxetane, if the presence of intramolecular chain transfer to a small extent is not excluded.
Phase separation by synthesis of semi‐interpenetrating network on the basis of polystyrene and poly(butyl methacrylate) from homogeneous solution
Authors: Lipatov Yury S. , Shilov Valery V. , Gomza Yury P. , Kovernik Grigory P. , Grigor'Eva Olga P. , Sergeyeva Ludmila M. 
Published: April 2003

AbstractPhase separation by semi‐interpenetrating polymeric network formation based on the copolymer styrene‐divinylbenzene (PS‐DVB) and poly(butyl methacrylate) (PBMA) was investigated by light scattering. The time for phase separation was measured as a function of the rate of the copolymerization reaction and of the composition of the initial blend. The time until the outset of phase separation decreases with increasing content of PBMA in the blend. The change in concentration of DVB does not influence the process of phase separation.
Autoxidation of thiols with tetrasodium cobalt(II)phthalocyaninetetrasulfonate, bound to poly(vinylamine), 3. Dependence on molecular weight
Authors: Brouwer Wilfried M. , Piet Pieter , German Anton L. 
Published: April 2003

AbstractPolymeric catalysts consisting of cobalt(II)phthalocyanine, CoPc(NaSO3)4, coordinatively bound to poly(vinylamine) of various molecular weight, were used as oxidation catalysts in the conversion of thiols to disulfides. The molecular weight of the polymeric ligand, poly(vinylamine), largely affects the reaction rate below a critical polymer concentration of about 0,01 w/v%. The activation enthalpy ΔH does not depend on the degree of polymerization (DP) of the polymeric ligand and from visible light spectra it appears that electron transfer of the thiolanion to Co(II) to yield Co(I) is favored when low instead of high molecular weight ligands are used. The observed catalytic oxidation rate of thiol is considerably higher for low molecular weight ligands (DP 20 – 40) in the low polymer concentration region. This may be attributed to a change in base strength in the micro‐environment of CoPc(NaSO3)4 due to conformational differences between low and high molecular weight ligands, manifested at low polymer concentration. When the ligand has no polymeric character, e. g. 1, 3‐propanediamine, low catalytic activity is observed.
Cinétique et mécanisme de la polymérisation de i'acrylamide initiée par le système réadox: Fe3+/complexe organique de Fe(III)/Na2S2O5
Authors: Cvetkovska Maja , Grčev Toma , Petrov Gjuro 
Published: April 2003

AbstractThe initiation of acrylamide polymerisation in aqueous media with a redox system of the type Fe3+/organic complex of Fe(III)/Na2S2O2 was studied. Several carboxylated amines containing the iminodiacetate group as a basic structural unit were used as complex forming reagents. A direct relation between complex stability and initiation efficiency was found. The polymerisation kinetics were studied with the most effective intiating system. Several kinetic parameters were determined and an essential relationship between polymerisation behaviour, polymer characteristices and component ratio of the initiation and polymerisation system was found. An attempt was made to explain these results.
Oxydation photothermique d'élastomères de polyuréthannes thermoplastiques, 4. Influence d'un oxyde à caractère photocatalytique
Authors: Gardette Jean‐Luc , Lemaire Jacques 
Published: April 2003

AbstractA photocatalyst like TiO2 may be introduced into a polymer to control the initiation process, to protect the photo‐instable products, and to limit the oxidation to a surface phenomenon. In the case of aromatic polyurethanes, the quantum yields of photocatalytic oxidation are low as compared with the quantum yields of direct photooxidation. Photoactive pigments behave as stabilisers for the oxidation pathway. On the other hand, the photocatalyst acts as a screen for the Fries photorearrangement products and inhibits their photooxidation. Yellowing of polyurethanes is partly due to the photoinduced oxidation and partly to the Fires photorearrangement products. It is shown that in the presence of photoactive pigments the yellowing of polyurethanes due to Fires photorearrangement is the most determental process.
Synthesis and properties of 9,10‐dialkoxyanthracenes as fluorescent probes specific of polyolefins and their application to orientation measurement in polyethylene
Authors: Young Chor Keung , Jasse Bruno 
Published: April 2003

Abstract9,10‐Dialkoxyanthracenes with an even number of carbon atoms n in the aliphatic chain from n = 2 to n = 18 were prepared by reaction of the corresponding bromoalkanes with the sodium salt of dihydroanthraquinone. Ultra‐violet and fluorescence spectra as well as life‐times of the excited state of these different fluorescent probes were determined. Higher terms with n ≥ 8 proved to be valuable to measure the amorphous phase orientation in polyolefins.
Les effets thermiques associés à la transition vetreuse de films de poly(téearéphatalate d'éthylène)
Authors: Chauchard Jacques , Lachenal Gilbert 
Published: April 2003

AbstractDifferential scanning calorimetry and thermomechanical analysis are used for examining the thermal behaviour of amorphous poly(ethylene terephthalate) films in the glass‐transition range. By variation of the heating rate between 0,2 and 100 K. · min−1, it is possible to obtain either an exotherm associated with a shrinkage, or an endotherm, or both of these phenomena. It is found that very low heating rates not only give rise to a retardation mechanism but also to a molecular rearrangement.
Functional polymers and sequential copolymers by phase transfer catalysis, 1. Alternating block copolymers of unsaturated polyethers and aromatic poly(ether sulfone)s
Authors: Percec Virgil , Auman Brian C. 
Published: April 2003

AbstractWilliamson etherification in the presence of phase transfer catalysts was successfully applied to the synthesis of alternating block copolymers and regular copolymers. Unsaturated polyethers(5a and 5b) containing chloroallylic (electrophilic) end groups (prepared from cis‐or trans‐1, 4‐dichloro‐2‐butene and Bisphenol A) and aromatic poly(ether sulfone)s (3a) containing terminal phenol (nucleophilic) groups were polycondensed in the presence of tetrabutylammonium hydrogen sulfate as phase transfer catalyst to give alternating block copolymers. The same telechelic polymers were chain‐extended with dinucleophilic or dielectrophilic monomers under similar reaction conditions. Both the regular copolymers and the alternating block copolymers were characterized by gel pormeation chromatography and DSC.
Preparation of a polysulfone by polycondensation of disodium 4,4′‐oxydibenzenesulfinate with 4‐bromomethylbenzyl bromide
Authors: Sato Moriyuki , Yokoyama Masaaki 
Published: April 2003

AbstractPolycondensations of 4‐bromomethylbenzyl bromide (p‐xylylene dibromid) (1) were carried out with 4,4′ ‐oxydibenzenesulfinate (3) in the presence of phase transfer catalysts, investigating the effect of reaction media, catalysts, monomer concentration, and reaction time. The polymer with the highest molecular weight was obtained at a monomer concentration of 8/15 mol/1 in nitrobenzene at 80°C for 48 h in the presence of tetrabutylammonium chloride. The characterization of the product by 1H NMR and IR spectra and by elemental analysis indicates the structure of a copolymer (5), containing both sulfinate and sulfone linkages in the main chain. Thermogravimetry of the product shows that its thermostability is lower than that of commercial poly(ether sulfone)s.
Structure of active species in the cationic polymerization of β‐propiolactone and ε‐caprolactone
Authors: Hofman Andrzej , Szymański Ryszard , Słomkowski Stanislaw , Penczek Stanislaw 
Published: April 2003

AbstractThe study of the structure of the end‐groups of poly(β‐propiolactone) and poly(ε‐caprolactone) by 1H, 31P{1H} NMR, and IR spectroscopy revealed that the mode of ring scission in the monomer in the first propagation step depends on the initiator used. In the initiation of the β‐propiolactone and ε‐caprolactone polymerization with halonium salts ((CH3)2Br⊕SbF6⊖ or (CH3)2I⊕SbF6F6⊖) the exocyclic oxygen atoms in the monomer molecules are attacked and oxonium ions are formed. The propagation steps proceed with alkyl‐oxygen bond scission in the active center and with attack at the exocyclic oxygen atom in the subsequent monomer molecule. Thus, the tertiary oxonium ions are the exclusive active species from the very beginning of the polymerization. Acylium cations (CH3CO⊕ SbF6⊖ or CH3CH2CO⊕SbF6⊖) as initiators attack both exo‐and endocyclic oxygen atoms in the monomers and the initiation proceeds with almost equal proportions of alkyl‐oxygen and acyl‐oxygen bond scission. Thus, in the polymerization of β‐propiolactone the concentration of the acylium growing species decreases with increasing number of propagation steps and finally the tertiary oxonium ions are becoming the exclusive growing species. In the polymerization of ε‐caprolactone the active acylium centers apart from propagation participate also in side reactions leading to the cleavage of a proton.
Polymers from renewable sources, 2. Kinetics and polyurethane formation from furan‐based diisocynates
Authors: Cawse John L. , Stanford John L. , Still Richard H. 
Published: April 2003

AbstractNovel furan‐based diisocyanates (2a – c) were reacted with 1‐butanol and basic kinetic studies were made. The results were compared with those obtained from 4,4′‐methylenediphenylene diisocyanate (1) under similar conditions. The kinetics of these model reactions were found to be complex even in the presence of added catalysts. The isocyanates 2 studied, were shown to behave as benzylic type compounds with reactivities intermediate between those of aryl and alkyl diisocyanates. Comparative studies were made on segmented copolyurethanes prepared from 1 and from a furfuryl diisocyanate 2a having structural similarity to 1. The diol components used in these studies were 1,4‐butanediol and polytetrahydrofuran. The segmented co‐polyurethanes prepared from the furfuryl diisocyanate can thus be derived from a single naturally occurring source material, namely furfuraldehyde. These polymers were shown by differential scanning calorimetry and dynamic mechanical analysis to possess properties comparable to analogous copolyurethanes derived from oil‐based sources.
Dilute solution properties of poly(methyl methacrylate) in acetonitrile + carbon tetrachloride mixtures
Authors: Vázquez Jesús , de Blas Luis , Prolongo Margarita G. , Masegosa Rosa M. , Hernández‐Fuentes Irmina , Horta Arturo 
Published: April 2003

AbstractHeterotactic poly(methyl methacrylate) (PMMA) is studied by light scattering and viscometry in the mixture acetonitrile + CCl4. Both liquids are poor solvents of PMMA, but their mixture is a very good solvent of this polymer. The total sorption potential of the coil is calculated from second virial coefficient and intrinsic viscosity results. Unperturbed dimensions, Mark‐Houwink exponent, Schulz‐Blaschke constant, and coil expansion factor are also determined. The enhanced total solvent sorption is larger in this mixture than in any other cosolvent system of PMMA thus far studied. This is due to the strong repulsive interactions between acetonitrile and CCl4. Such interactions also determine the inversion in preferential sorption that occurs close to equimolar composition. Acetonitrile can interact favourably with the ester group of PMMA and unfavourably with its methylene backbone. The role of such opposing interactions and of liquid order in acetonitrile are taken into account to discuss the results.
Molecular modelling of the anisotropy of motion in polysaccharides: an example
Authors: Gagnaire Didier , Pérez Serge , Tran Vinh 
Published: April 2003

AbstractA qualitative analysis of NMR relaxation data is reported, using motional models based on the consideration of conformational states arising from the architectural specificity of the different building units of a polysaccharide. The choice of a pertinent referential axis, such as either a local helical axis or a local inertial axis is discussed.
Über polymere 4‐vinylimidazolide und deren verwendung als acylierungsreagenzien
Authors: Manecke Georg , Stärk Michael 
Published: April 2003

AbstractSeveral copolymers of 4(5)‐vinylimidazole (1a) containing different amounts of divinyl‐benzene (DVB) as crosslinking agent and also copolymers of 1a (crosslinked, 4 mol‐%) with styrene, 4‐vinylpyridine, 1‐vinylimidazole, or 4‐vinylbenzoic acid were obtained by radical polymerisation. The pendant imidazole‐groups of all of these polymers could be acylated in their 1‐position. The swellability of the resulting polymeric N‐acylated imidazoles in suitable solvents was investigated. They were used for the acylation of amines and alcohols, variing the mole ratio reactive polymer/substrate, the reaction time, and the solvent. A gradual reacitivity was found for the reaction with low molecular mass compounds according to the nucleophilicity of the substrates. Ethanolamine could be selectively N‐acetylated and in the case of the mono‐trifluoroacetylation of hexamethylenediamine significantly high yields of mono‐acylated product were obtained. After the reaction the polymers could be regenerated without any loss of activity.
Etude de la synthèse et de la microstructure du polyallylbenzène
Authors: Boiteux‐Steffan Gisèle , Pham Quang Tho 
Published: April 2003

AbstractPoly(allylbenzene)s were synthetised by Ziegler‐Natta catalysts: {VCl3 + Al[CH2CH(CH3)2]3} and {TiCl4 + Al[CH2CH(CH3)2]3}. Two different polymers were obtained. Examination of their microstructures by IR and 1H13C NMR spectroscopy suggests that one of the polymerization mechanisms proceeds via isomerization of allylbenzene.
Formation of high molecular weight polythiiranes in aqueous‐organic media
Authors: Amerik Yuri B. , Shirokova Lidia A. , Toltchinsky Isaak M. , Krentsel Boris A. 
Published: April 2003

AbstractThe influence of water on the polymerization of thiirane and 2‐methylthiirane with CdCO3 was studied. The polymerization process takes place only when a large interface monomer‐water is formed. This is achieved by the presence of an amount of water in the reaction mixture which is comparable with that of the monomer. The polarity of the solvent does not influence the rate of formation of poly(2‐methylthiirane). The polymerization is carried out in the mass of monomer or in the presence of an alcohol and a solvent not miscible with water.
On the kinetics and mechanism of thermal degradation of polystyrene, 2. Formation of volatile compounds
Authors: Schröder Ulrich K. O. , Ebert Klaus H. , Hamielec Archie W. 
Published: April 2003

AbstractThermal degradation of polystyrene (PS) was carried out in the absence of oxygen between 292 and 336°C. The formed volatile products were analysed qualitatively and quantitatively by means of gas charomatography. It was found that the composition of the volatile fraction is a function of conversion and independent of temperature for most of the products. A radical chain mechanism is proposed to explain these experimental results.
Kinetics of the polymerization of styrene with butoxytitanium trichloride and trialkylaluminium
Authors: Sehra Jagdish C. , Gundiah Subbaraya 
Published: April 2003

AbstractThe kinetics of polymerization of styrene in heptane was investigated using butoxytitanium trichloride and triethylaluminium/triisobutylaluminium as cocatalysts. A steady state polymerization after an initial period of declining rates lasting for 20 – 60 min was observed. Both the catalysts systems polymerize styrene at a slow rate ( ≈ 10−6 mol · dm−3 · s−1). The steady state rates show a maximum at an [A1] : [Ti] ratio of 1,5 and exhibit a first‐order rate law with reference to both the monomer and the catalyst. Addition of triethylamine, an electron donor, greatly influences the rates of polymerization when triethylaluminium is used, whereas in the case of triisobutylaluminium, the rates are not greatly influenced by the presence or absence of triethylamine. The effect of the electron donor on the rates of polymerization can be explained by the competitive complexation of the alkylaluminium and the electron donor at the active site. The overall activation energy of polymerization (44 – 46 kJ · mol−1) is in accord with a coordinated anionic mechanism. An alkylated alkoxytitanium halide species as the chemical entity affecting polymerization is suggested.