bluuebunny/crossref_metadata_2025_split huggingface dataset:
Herstellung und eigenschaften von polyacenaphthylen, 1. Die darstellung von oligoacenaphthylene mit funktionellen endgruppen
Authors: Springer Jürgen , Win Tin 
Published: April 2003

AbstractExperiments regarding the anionic polymerization of acenaphthylene with different initiators (lithiumnaphthalene complex, 1,2‐diphenylethylenedilithium, 1,1,4,4‐tetraphenyltetramethylenedilithium and butyllithium) and solvents (tetrahydrofuran and benzene) show that only short chain (P̄≈ 20) and coloured polymers with broad molecular weight distribution are obtained, because of chain transfer reactions to the monomer. A mechanism of this polymerization is proposed. By radical polymerization short chain polyacenaphthylene with definite end groups can be obtained.
Laccase‐catalyzed polymerization of urushiol in precisely confined Japanese lacquer system
Authors: Kumanotani Ju 
Published: April 2003

AbstractJapanese lacquer is a sole, enzymatically drying natural lacquer, giving films with excellent durability. Oligomerization of urushiol (1) (a major component of the lacquer) in the lacquer system was reviewed. The enzymic formation of the urushiol‐quinone (3) from urushiol was studied by laccase‐catalyzed reactions with pyrocatechols. On the basis of the separated urushiol dimers in both the lacquer and model reaction systems, a nonenzymatic CC and CO coupling reaction of the urushiol‐quinone with the unsaturated chain or with the nucleus of urushiol is discussed as significant reaction path in the polymerization of Japanes lacquer. The films of the lacquer made by a mild oxidation process, a technique applied for so long time in practice, retained their dynamechanical properties completely over 16 years.
Zur struktur der produkte der reaktion von 2‐cyano‐2‐propylradikalen mit 1,4‐benzochinon
Authors: Gleixner Günther , Breitenbach Johann Wolfgang , Olaj Oskar Friedrich 
Published: April 2003

AbstractThe products of the reaction of 2‐cyano‐2‐propyl radicals with 1,4‐benzoquinone in toluene solution have been investigated by 1H NMR spectroscopy and mass spectroscopy. In agreement with the findings of Bickel and Waters the main reaction products are the hydroquinone monoether 1 and the hydroquinone diether 2. In addition two ringsubstituted products, 5 and 6, have been obtained. The structures 3 and 4, which have been proposed for the main products by Yassin and Rizk, are shown to be in error.
Synthèse et réactions photochimiques d'homopolymères et de copolymères de la p‐vinylbenzophénone et du vinylferrocène
Authors: Sánchez Germán , Weill Gilbert , Knoesel Roger 
Published: April 2003

AbstractPoly(p‐vinylbenzophenone), (poly[1‐(4‐benzoylphenyl)ethylene]), (PVB) has been synthesized for the first time directly from its monomer p‐vinylbenzophenone (VB) the preparation of which was improved. In a second step, copolymers containing blocks of photosensitive VB units separated by isolated quenching vinylferrocene (VF) units have been prepared. PVB and the VB‐VF copolymers were irradiated in the presence of isopropyl alcohol in benzene solutions. The benzophenone groups inserted in these macromolecular chains obey the same reaction scheme as the photoreduction of the small molecule of benzophenone. However, recombination of the radicals located along the polymeric chain leads to intra‐ and intermolecular reactions changing drastically the macromolecular morphology by the formation of cycles and networks and by chain scissions. The quantum yields of the photochemical transformations were measured, but they could not be related quantitatively to morphological parameters. In all cases the ferrocene group inhibits strongly the photochemical reaction.
Electron spin resonance study of polymer degradation, 2. Photolysis at 365 nm of polystyrene containing benzophenone
Authors: David Christiane , Piret Willy , Sakaguchi Masato , Geuskens Georges 
Published: April 2003

AbstractPolystyrene containing benzophenone, present either as an additive or linked to the polymer chain has been irradiated at 365 nm at room temperature and the ESR spectra were analyzed. When benzophenone is linked to the chain, equal proportions of the “ketyl macroradical” 2 and of the “polystyryl radical” 3 resulting from abstraction of the tertiary H‐atom of the styrene unit are detected. These decay on warming the sample and at 410K only about 20% of the ketyl radicals is still present. Very fast radical decay occurs at room temperature on addition of oxygen to samples where radicals 2 and 3 are trapped as pairs. In samples annealed at 410K, the isolated ketyl radicals decay slowlier by second order kinetics under the same conditions. If benzophenone is present as an additive, only a small amount of isolated polystyryl radical 3 is trapped at room temperature since most of the polymer radicals have reacted with the mobile ketyl radicals. These isolated radicals 3 decay by second order kinetics on addition of oxygen.
Polymere hydrochinoncarbonamide. Darstellung von redoxharzen auf der basis von N‐(3‐vinylphenyl)‐2,5‐dihydroxy‐4‐methylbenzamid bzw. N‐(2,5‐dihydroxy‐4‐methylphenyl)‐4‐vinylbenzamid
Authors: Manecke Georg , Krämer Andreas , Wehr Gregor 
Published: April 2003

AbstractN‐(3‐Vinylphenyl)‐2,5‐dimethoxy‐4‐methylbenzamide (3) was synthesized. By copolymerization of 3 and of N‐(2,5‐dimethoxy‐4‐methylphenyl)‐4‐vinylbenzamide, respectively, with 4‐vinylpyridine and 1,4‐divinylbenzene protected redox resins were obtained. By removal of the protective groups the corresponding free redox resins were obtained. Their chemical stability and redox capacities were investigated. The influence of the anilinocarbonyl group on the midpoint potential of the hydroquinone/quinone system was studied on the model compound N‐phenyl‐2,5‐dihydroxy‐4‐methylbenzamide.
Synthesis and activity of a polymer which contains insulin covalently bound on a copolymer of N‐(2‐hydroxypropyl)methacrylamide and N‐methacryloyldiglycyl p‐nitrophenyl ester
Authors: Chytrý Vladimír , Vrána Antonín , Kopeček Jindřich 
Published: April 2003

AbstractInsulin bound on a polymer carrier has been prepared by a reaction of insulin with the copolymer of N‐(2‐hydroxypropyl)methacrylamide and N‐methacryloyldiglycyl p‐nitrophenyl ester. The product isolated by gel chromatography contains ca. 60 wt.‐% of insulin. It preserves ca. 10% of the radioimmunoreactivity of the starting insulin, and in biological tests exhibits a slowed‐down onset and a slight prolongation of the hypoglycaemic effect.
Strukturuntersuchung von polyestern durch direkten abbau im massenspektrometer, 3. Poly‐β‐propiolacton, poly‐β‐pivalolacton und poly‐δ‐valerolacton
Authors: Kricheldorf Hans R. , Lüderwald Ingo 
Published: April 2003

AbstractPoly(oxycarbonylethylene) (poly‐β‐propiolactone), poly(oxycarbonyl‐1,1‐dimeothylethylene) (poly‐β‐pivalolactone), and poly(oxycarbonyltetramethylene) (poly‐δ‐valerolactone) were pyrolyzed directly in the ion source of a mass spectrometer and their thermal and electron impact induced degradation mechanisms are established. Poly‐β‐propiolactone is thermally degraded by rupture of the OCH2‐bond by a cis elimination to give carboxyl and acryloyl endgroups, whereas poly‐δ‐valerolactone depolymerizes to δ‐valerolactone. Poly‐β‐pivalolactone degrades thermally to cyclic oligomers of pivalolactone, which could be proved by a separated pyrolysis and IR‐spectroscopy and gel chromatography.
Syndiotactic poly(leucine)
Authors: Fick Fritz‐Georg , Semen John , Elias Hans‐Georg 
Published: April 2003

AbstractN‐(tert‐Butoxycarbonyl)‐L‐leucyl‐D‐leucyl‐L‐leucyl‐D‐leucine tetrapeptide was synthesized from L‐ and D‐leucine α‐amino acids by conventional coupling methods. This tetrapeptide was transformed into an activated (polymerizable) tetrapeptide by conversion to the pentachlorophenyl ester and subsequent removal of the tert‐butoxycarbonyl group. Condensation polymerizations of the activated tetrapeptide were performed in various solvents with triethylamine and N,N‐diethyl‐1‐amino‐2‐propanol bases. Molar masses (“molecular weights”) of the resulting polymers were estimated to be in excess of 34000 g/mol. From optical rotation measurements in trifluoroacetic acid solution, it was found that the polymers were highly syndiotactic, although a small amount of isomerization (0,9–2,1%) occurred to yield polymers with a small excess of L‐leucine residues. The degree of isomerization decreased with decreasing base strength and concentration and with decreasing polarity of the solvent; these effects were explained in terms of the simultaneous enolization and/or oxazolone‐formation reactions.Preliminary studies of the conformation of syndiotactic poly(leucine) were performed with X‐ray diffraction, NMR, IR and optical rotation methods. It was concluded that syndiotactic poly(leucine) most probably exists in a π‐helical conformation with a preferred screw sense in both the solid state and in chloroform solution. NMR and optical rotation data on solutions in trifluoroacetic acid/chloroform showed that the polymer exhibits a conformational transition in the region of 4–10% trifluoroacetic acid content.
Synthesis of dithiocarbamates from linear poly(iminoethylene) and some model compounds
Authors: Ivin Kenneth J. , Lillie Edwin D. 
Published: April 2003

AbstractReaction of linear poly(iminoethylene) with carbon disulfide in the presence of sodium hydroxide gives a product in which every NH group is replaced by NCS⊖Na⊕. In the absence of sodium hydroxide about one NH group in two is replaced by NCS2H and there is a random distribution of such groups. Evidence for these reactions was obtained from 13C NMR spectra, which were interpreted on the basis of the chemical shifts of dithiocarbamates derived from three model diamines.
Mutarotation of α‐D‐glucose catalyzed by poly(4‐vinylpyridine) and poly(4‐vinylpyridinium hydrochloride) in N,N‐dimethylformamide solutions
Authors: Fujimori Kiyohisa 
Published: April 2003

AbstractThe rate of mutarotation of α‐D‐glucopyranose catalyzed by polymers of 4‐vinylpyridine (4VP) was observed in N,N‐dimethylformamide (DMF) solutions. Poly(styrene‐co‐4VP·HCI) and poly(4VP·HCl) were active while poly(4VP) of various average molecular weights showed little catalytic activity. p‐Chlorophenol‐poly(4VP) catalyst pair in DMF and poly(4VP·HCl)‐poly(4VP) catalyst pair in DMF/methanol mixed solvent showed a catalysis of bifunctional mechanism.
Asymmetric synthesis catalyzed by oligo((S)‐alanine)
Authors: Ueyanagi Kaoru , Inoue Shohei 
Published: April 2003

AbstractIn the asymmetric addition of 1‐dodecanethiol to isopropenyl methyl ketone catalyzed by the terminal primary amino group of oligo((S)‐alanine) (1c), the trimer and the tetramer in β‐conformation gave much higher optical yield than the monomer and the dimer in random conformation. A similar result was obtained in the catalysis by β‐alanyl‐poly((S)‐alanine) (3).
Einfluß von hydrazinderivaten auf die radikalische styrolpolymerisation
Authors: Hallensleben Manfred L. , Hoser Wolfram F. 
Published: April 2003

AbstractThe radical polymerization of styrene was investigated in the presence of six different hydrazine derivatives. These compounds were selected in view of the nitrogen radicals, either from the aminyl or the hydrazyl type, resulting upon carbon radical attack. A distinct dependence of the rate of polymerization on the nature of hydrazine substituents was detected in thermally as well as radically (AIBN) induced polymerization. 1,2‐Diacetylhydrazine (13), 1,2‐bis(p‐nitrophenyl)hydrazine (16), 1,2‐diacetyl‐1,2‐diphenylhydrazine (15), and 1,2‐dimethylhydrazine (12) act as retarding compounds whereas 1,2‐diphenylhydrazine (14) and tetraphenylhydrazine (1) are inhibitors. The transfer constants were calculated from the Mayo equation to be 0,02 for 12, 0,06 for 13, 0,1 for 15, 0,8 for 16, 0,9 for 14, and 5,6 for 1. Any influence of polymerization temperature on the chain transfer constant was not observed. From model reactions only hydrazyl radicals were detected.
Segmental motions of spin‐labelled poly(ethylene oxide) in dilute solution
Authors: Braun Dietrich , Törmälä Pertti 
Published: April 2003

AbstractThe rotational correlation times (τ) of spin‐labelled poly(ethylene oxide), (Mw=20 000) were measured in benzene, pyridine and water. It was found that τ is independent of polymer concentration (c) when c<0,15 g/(ml solvent). In dilute solutions τ values of 49 ps, 43 ps and 100 ps in benzene, pyridine and water at 293 K were obtained. A comparison with results of dielectric relaxation and nuclear magnetic resonance measurements indicated that τdiel. < τ13CNMR < τspin‐labelling < τ1H NMR. Values 17.7±2,2 kJ/mol and 17,3kJ/mol for the potential barrier of local conformational changes of PEO in pyridine and water solutions were obtained.The apparent hydrodynamic radii (0,35–0,46 nm) indicated the loosely arranged random coil state of the polymer molecules in solution at 293 K.
Kinetische und morphologische untersuchungen zur polymerisation von oxacyclischen monomeren im festen zustand, 2. Zur morphologie der bei der straheleninduzierten polymerisation von trioxan und tetroxan entstehenden poly(oxymethylene)
Authors: Muñoz‐Escalona Antonio 
Published: April 2003

AbstractIn order to clarify the reaction mechanism of the solid‐state polymerisation of 1,3,5‐trioxane and 1,3,5,7‐tetroxane as induced by gamma‐radiation, the nascent textures and morphology of poly(oxymethylene) crystals were studied with light and transmission electron microscopy, X‐ray scattering and differential thermal analysis techniques. In both cases poly(oxymethylene) crystals with fibrous morphology and “twin‐structure” are obtained. The polymerization of 1,3,5,7‐tetroxane gives rise to the formation of crystals where the preferred orientation of the polymer chain is the monomer b‐axis; however, the fibrils showed ripples perpendicular to the main chain direction at a 70–240Å long period that depends extremely on the polymerization temperature. In the polymerization of 1,3,5‐trioxane, POM crystals with 60% of the polymer chains in the direction of the monomer c‐axis are obtained. The remaining chains are found in the “twin sub‐crystals”. Dark field electron micrographs showed the sub‐crystals to be an integral part of the fibrils. The material in the twin direction decreases, when the polymerization temperature or the yields increases; it never amounts to less than 30%. These results and the misfit between the lattices of the monomers and the nascent polymer indicate that the reactions which take place occur according to a simultaneous polymerization and crystallization mechanism through the gasphase. The polymerization process occurs easier at higher temperatures near the monomers' melting point due to the increase of monomer vapor pressure and diffusion processes in the monomer crystals. Molecular models of the chain growth are developed on the basis of the morphological observations.
Influence de la nature du solvant sur les propriétés physico‐chimiques des polyamides aromatiques en solution diluée
Authors: Millaud Bernard , Strazielle Claude 
Published: April 2003

AbstractThe dilute solution properties of some aromatic polyamides like: poly(1,4‐phenyleneterephthalamide), (or poly(imino‐1,4‐phenyleneiminoterephthaloyl)), poly(parabenzamide), (or poly(imino‐1,4‐phenylenecarbonyl)), and some chlorinated derivatives of poly(1,4‐phenyleneterephthalamide) have been investigated. Solvents like 96% sulfuric acid, methanesulfonic and chlorosulfonic acid and also N,N‐dimethylacetamide + LiCl have been used. An increase of the intrinsic viscosity and of the exponent of the viscosity law when we use methanesulfonic and chlorosulfonic acids has been observed and is explained by an increase of the rigidity and hydrodynamic diameter of the molecule. The measurements of the radius of gyration, and optical anisotropy confirm this. In N,N‐dimethylacetamide, the molecules of poly(parabenzamide) exhibit an association which depends on parameters such as percentage of LiCl and temperature.
Catalysis of olefin transformation by tungsten complexes, 6. Equilibrium oligomer concentration in the polymerization of 1,5‐cyclooctadiene
Authors: Chauvin Yves , Commereuc Dominique , Zaborowski Georges 
Published: April 2003

AbstractDepending on the concentration, the ring‐opening polymerization of 1,5‐cyclooctadiene, or the metathesis of poly(2‐butynylene), affords either cyclic oligomers or a mixture of cyclic oligomers and high molecular weight polymer, the 1,5‐cyclooctadiene being not involved in the equilibrium. The concentration of oligomers at the equilibrium depends only on the nature of the solvent, and in the case of an aromatic solvent also on the total concentration of the reactants. The thermodynamic and kinetic pathways of the reaction are discussed.
Non‐ideality in vinyl polymerisation, 2. Free‐radical polymerisation of styrene with azoisobutyronitrile
Authors: Deb Pramil C. , Gaba Ishwar D. 
Published: April 2003

AbstractPolymerisation of styrene in benzene initiated by azoisobutyronitrile (AIBN) was carried out at 60°C covering a wide range of concentrations of both monomer and initiator. It is found that the monomer concentration has only little effect on the characteristic constant of primary radical termination, kprt/(kikp). This is explained on the basis of the fact that the secondary dissociation of the initial primary radicals occurs very quickly (ca. 10−11 s), thus allowing no chance of competition for the initiation process. This is in sharp contrast to the secondary dissociation of the benzoyloxyl radical which has a much longer life‐time (ca. 10−9 s). However, it is found that the polymerisation constant 2fkkdk/kt is dependent on monomer concentration and increases with the latter. The characteristic constant has also been determined at 40, 50, 70, and 80°C and the energy of activation corresponding to the initiation process obtained therefrom is about 66kJ/mol. This is appreciably higher than the value generally assumed (Ei≈Ep = 32,6kJ/mol) and could not be explained on the basis of experimental error. Ei is moreover very near to the value obtained for benzoyl peroxide initiated polymerisation of styrene determined earlier. Thus it seems that the initiation and propagation processes involve different activation energies and not the same as has hitherto been assumed.
Phosphorescence quenching and photostabilising efficiencies of ultraviolet stabilisers in commercial polypropylene
Authors: Allen Norman S. , Homer John , McKellar John F. 
Published: April 2003

AbstractThe phosphorescence quenching efficiency of a wide range of ultraviolet stabilisers has been studied in polypropylene and their performance compared with their photostabilising action in the polymer. It is concluded that the quenching of photoactive triplet carbonyl impurities may contribute, to a greater or lesser degree, towards their stabilising action. However, individually no direct correlation between quenching efficiency and stabilising action was observed. Indeed the very interesting observation is made that a highly efficient stabiliser of the hindered amine type shows no phosphorescence quenching at all.
Über die Druckabhängigkeit der viskoelastischen und physikalisch‐chemischen Eigenschaften von Polymeren, 7. Einfluß des Lösungsmittels para‐Xylol auf das Schmelzen und Kristallisieren von Polyethylen
Authors: Karl Veit‐Holger , Asmussen Frithjof , Ueberreiter Kurt 
Published: April 2003

AbstractMelting and crystallization of polyethylene (PE) with various amounts of xylene is investigated by pressure dependent volume‐temperature curves. These can be calculated by a reduction formula described earlier. Flory's formula for lowering of the melting point of polymers by solvents proves to be applicable also for high pressures.
The synthesis of epoxy resins in dipolar, aprotic solvents
Authors: Rokicki Gabriel , Kuran Witold , Nowiński Andrzej 
Published: April 2003

AbstractThe snythesis of low molecular weight epoxy resins from various alkali metal diphenolates and 1‐halo‐2,3‐epoxyalkanes in dipolar, aprotic solvents is described. The resulting epoxy resins have no oxy‐(2‐hydroxytrimethylene)oxy groups as a consequence of a lack of mobile protons in the reaction system. The effect of various factors on the reaction course was determined by kinetic measurements.
Free radical polymerization kinetics of n‐lauryl methacrylate
Authors: Mahabadi Hadi Kh. , O'Driscoll Kenneth F. 
Published: April 2003

AbstractThe kinetics of free radical polymerization of n‐lauryl methacrylate (dodecyl methacrylate) were studied at 60 and 80°C in bulk and in benzene solution. The analysis of the data showed the kinetic results deviated from classical behaviour and that this deviation could be explained by the chain length dependence of the diffusion controlled termination rate constant, Kt. Primary radical termination is explicitly considered and rejected as being insignificant in this work. Because of its lessened flexibility poly(n‐lauryl methacrylate) shows a greater chain length dependence for Kt than does poly(methylmethacrylate).
Comparative study of the hydrodynamic properties of cellulose and amylose tricarbanilates in dilute solutions viscosity, sedimentation and diffusion measurements in 1,4‐dioxane in the molecular weight range of 500 ≤M≤ 5·106
Authors: Sutter Wolfgang , Burchard Walther 
Published: April 2003

AbstractComparative hydrodynamic measurements were performed for cellulose tricarbanilates (CTC) and amylose tricarbanilates (ATC)—covering the whole region from the monomer up to the highest available molecular weight of 3,6 . 106.The intrinsic viscosity vs. molecular weight relationships exhibit in both cases characteristic S‐shaped curves. In the region of oligomers the intrinsic viscosities remain almost constant; it follows then a steep increase with molecular weight which finally flattens out to constant slopes for high molecular weights. In the high molecular weight region the curves may be approximated by Kuhn‐Mark‐Houwink equations with exponents of 0,90 and 0,88 for CTC and ATC, respectively. The intrinsic viscosities are by a factor two smaller for ATC than for CTC. The S‐shaped curves are interpreted as a result of the finite cross‐section of the chains and a certain chain stiffness. Stockmayer‐Fixman plots gave strongly bent curves which is shown to be due to chain rigidity.Sedimentation coefficients and diffusion constants as functions of the molecular weight approach straight lines in a double logarithmic plot for large molecular weights; for shorter chains characteristically bent curves are obtained which are ascribed to chain stiffness and finite chain cross‐section.The origin of chain stiffness in CTC is discussed to be due to H‐bond formation between the NH‐group of the substituent in C2 position of the sugar ring and a CO‐group of the substituent in C6 of a neighbouring repeating unit. This interpretation is supported by the low viscosity of mannan tricarbanilate (MTC), in which the facility of H‐bond formation is lost and higher flexibility is obtained.
On the polymerization of crystalline 1,4‐diethynylnaphthalene, 2 The reaction mechanism
Authors: Rohde Ottmar , Wegner Gerhard 
Published: April 2003

AbstractCrystalline 1,4‐diethynylnaphthalene (1) is photochemically polymerized in the solid state by a radical mechanism. Only the chain initiation step is induced by light, whereas chain propagation also occurs in the dark. The polymerization is controlled by diffusion processes within partially melted domains of the crystal, ultimately leading to a completely disordered system. The reaction rate, however, also depends on the packing of the monomer in the crystal lattice and—in the beginning of the reaction—the polymer chains have a preferential orientation with regard to the crystal axes of the monomer. Radical polymerization in solution indicates that—due to the lack of effective chain termination steps—1 can be polymerized rather effectively as compared to other acetylenes. The photochemically induced polymerization is approximately of second order with regard to monomer concentration.