bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ringförmige verbindungen – bessere lösungsmittel für makromoleküle als die entsprechenden linearen
Authors: Horacek Heinrich 
Published: April 2003

AbstractPolymers were dissolved in cyclic and linear compounds, in their di‐, tri‐ and n‐meres or in hydrocarbons, ethers, ketones, alcohols, chlorides and amines. Solutions of macromolecules in corresponding pairs of solvents exerted different activities, viscosities, and excess volumina. This result is explained by the measured diagrams of state or phases: For solutions of cyclic compounds the temperatures of experiments are farther away from those of phase separation; therefore, lower activities, higher viscosities, and smaller excess volumina are observed. From the larger area of infinite miscibility the common rule is derived that cyclic compounds are better solvents for macromolecules than the corresponding linear ones. The higher power of dissolution becomes evident considering the reduction of endgroups by polymerization as well as by cyclization. This compression of material increases density, viscosity, decreases cubic coefficient of expansion, compressibility and thus diminishes the difference between polymers and solvents. As the solubility parameter takes account of the more dense state of polymers, it is in many cases greater than that one of monomer or low molecular compound, which has to be adjusted to that of the polymer by cyclization. Recent thermodynamic calculations describe qualitatively the different dissolution power of cyclic and linear solvents by their different, P, V, T‐data.
Polymerization and quaternization of 1‐(2‐diethylaminoethyl)‐4‐vinylbenzene: A new cationic polyelectrolyte
Authors: Kataoka Kazunori , Tsuruta Teiji 
Published: April 2003

AbstractDiethylamination of 1,4‐divinylbenzene catalyzed by lithium diethylamide gave rise to 1‐(2‐diethylaminoethyl)‐4‐vinylbenzene (3), quantitatively. Subsequent quaternization of 3 with ethyl bromide gave a cationic monomer, 4‐vinylphenethyltriethylammonium bromide (7). High molecular weight polymers, poly[1‐{4‐[2‐(diethylamino)ethyl]phenyl}ethylene] (5) and poly[1‐{4‐[2‐(triethylammonio)ethyl]phenyl}ethylene bromide] (8), were prepared from 3 and 7, respectively, by using radical initiators, especially with redox‐type ones. Anionic polymerization of 3 was also carried out. The relationship between the polymerization condition and the stereoregularity of the polymer was studied by Carbon‐13 NMR spectroscopy. A polyion complex (10) was prepared from 8 in combination with poly(sodium 4‐vinylbenzenesulfonate) (9) to evaluate its properties as biomedical material.
Cationic degradation of poly(propylene sulfide)
Authors: Simonds Ronald P. , Goethals Eric J. 
Published: April 2003

AbstractIntroduction of small amounts of sulfonium ions in poly(thiopropylene) (poly(propylene sulfide)) by means of triethyloxonium tetrafluoroborate was found to result in a rapid degradation reaction, first leading to low molecular weight polymers and ultimately to a mixture of low molecular weight cyclic products and propene. The reaction mixtures were analyzed by gas liquid chromatography, mass spectroscopy and, when the compounds could be isolated in sufficient amounts, by 1H NMR spectroscopy. The composition of the end product mixture was shown to depend on the concentration of sulfonium ions introduced at the beginning. With low initiator concentrations (≈ 10−3 mol.l−1) the main degradation product was found to be cyclic tetramer accompanied by decreasing amounts of cyclic pentamer, hexamer etc., and with high initiator concentrations (> 10−2 mol.l−1) the main degradation products are a mixture of dimethyl‐1,2,5‐trithiepanes and propene.
Réticulation anionique du polystyrène en présence de chaînes polymériques libres
Authors: Widmaier Jean‐Michel 
Published: April 2003

AbstractSemi‐interpenetrating polymeric networks based on polystyrene were prepared by anionic polymerisation. Factors affecting synthesis, such as composition, molecular weight of either the unattached polystyrene or the polystyrene between crosslinks, have been varied. Their effect on network formation was examined by extraction experiments and swelling measurements.
Statistics of polyfunctional polycondensates formed under restrictions
Authors: Müller Michael , Burchard Walther 
Published: April 2003

AbstractThe scattering behaviour and the critical conditions where gelation takes place have been calculated for polycondensates formed under constraints. The general model includes fully random and stringently restricted reactions as limiting cases. Also polycondensates of glycerine‐type monomers are included as special cases. The particle scattering factors of the f‐functional random polycondensates differ remarkably from those polycondensates formed under strict constraints. The former show a Kratky plot of a simple curve, independent of the magnitude of the molecular weight and the number of functional groups, and the curve approaches a constant asymptote of u2·Pz(u)=3, the latter exhibits a maximum at u2=6 which becomes more pronounced with increasing molecular weight, (u2 = 〈S2〉zh2, with h, the value of the scattering vector). The scattering curves of the polycondensates formed under weak constraints show at low molecular weights the same behaviour as those formed under stringent constraints, but approach the behaviour of random polycondensates at large molecular weights. The scattering curves of the glycerine‐type polycondensates show no deviations in shape from random polycondensates.
Synthèse et étude structurale de copolymères séquencés polyisoprène‐poly(vinyl‐2 pyridine) et polyisoprène‐poly(vinyl‐4 pyridine)
Authors: Rossi Joel , Gallot Bernard 
Published: April 2003

AbstractBlock copolymers poly(1,2‐ and 3,4‐isoprene)‐poly(2‐vinylpyridine), poly(cis‐1,4‐isoprene)‐poly(2‐vinyl‐pyridine) and poly(cis 1,4‐isoprene)‐poly(4‐vinylpyridine) were synthesized by anionic polymerization. Their structure in the dry state and in concentrated solution was studied before and after polymerization of the solvent by low angle X ray scattering and by electron microscopy. The existence of lamellar and cylindrical structures was demonstrated. The effects of the copolymer composition, the nature, the concentration and the polymerization of the solvent on the type of structure adopted by the copolymer and on its geometrical parameters were established.
Copolymerisation of 4,4′‐divinylbiphenyl and of 4,4′‐diisopropenylbiphenyl with styrene in solution
Authors: Holdaway Ian , Haward Robert N. , Parsons Ian W. 
Published: April 2003

AbstractStyrene has been copolymerised with 4,4′‐divinylbiphenyl and with 4,4′‐diisopropenylbiphenyl in 15% toluene solution at 95°C. The copolymers have been analysed via UV spectroscopy, to give estimates of total crosslinker incorporated and of the number of pendant double bonds remaining. Extrapolation of the results—including viscometry—to zero conversion indicates that both crosslinkers form intramolecular linkages (rings). These rings appear to be comparable in size with those formed with p‐divinylbenzene, but to occur rather more frequently. Estimates of copolymerisation reactivity ratios r1 (styrene=1) are, for 4,4′‐divinylbiphenyl 0,77, for 4,4′‐diisopropenylbiphenyl 1,3. It is concluded that, contrary to a previous suggestion, increasing separation of reactive groups leads to more, not less, intramolecular reaction.
Calorimetric study on the formation of polymer complexes through electrostatic interaction and hydrogen bonding
Authors: Abe Koji , Ohno Hiroyuki , Nii Atsushi , Tsuchida Eishun 
Published: April 2003

AbstractPolymer complexes were formed through electrostatic interaction in poly(methacrylic acid)‐integral type polycation systems and hydrogen bonding in the poly(methacrylic acid)‐poly(N‐vinyl‐2‐pyrrolidone) system in several solvents. The composition of the polyelectrolyte complex was affected by the chemical properties of solvents, e.g., the dissociation of the component polyelectrolyte was interferred with decreasing the polarity of the solvent. The heats of mixing in case of the combination of poly(methacrylic acid)‐poly(N‐vinyl‐2‐pyrrolidone) were negative in N,N‐dimethylformamide but they were positive in water. In polyelectrolyte complex systems, they could not be measured by reason of some experimental difficulties. These results indicate that solvation of the component polymers is very important to clarify the mechanism of the formation of polymer complexes.
1H NMR and 13C NMR spectra of stereoisomers of the methyl methacrylate “dimer”: Dimethyl 2‐methoxymethyl‐2,4‐dimethylglutarate
Authors: Fujishige Shoei 
Published: April 2003

AbstractMethyl methacrylate oligomers were prepared through anionic oligomerization initiated with sodium methoxide. The pure dimer, isolated by careful fractional distillation, was subjected further to a preparativescale liquid chromatography and separated into its constituent stereoisomers. 1H NMR and 13C NMR spectra of the stereoisomers were studied in various organic solvents at different temperatures. An a priori assignment of the resonance patterns was attained successfully and the fine structures of the spectra were characterized with respect to the stereospecific features of the chemical structure of the stereoisomers.
Measured and calculated solubility of polymers in mixed solvents: Co‐nonsolvency
Authors: Wolf B. A. , Willms M. M. 
Published: April 2003

AbstractThe phenomenon of co‐nonsolvency, i.e. the formation of nonsolvents by mixing two solvents, was studied for the system N,N‐dimethylformamide/cyclohexane/polystyrene (DMF/CH/PS) which is characterized by the fact that the components of the mixed solvent are only incompletely miscible below 48,6°C. A number of quasibinary sections (stepwise addition of the second solvent to given solutions of the polymer in the first solvent) for a sample (M = 110000) of high molecular uniformity yielded a cloud point surface which gives “island curves” (closed solubility gaps) for constant temperatures between the critical temperature of DMF/CH and the top of the cloud point surface (51,3°C). The attainment of equilibrium is facilitated by the addition of DMF to CH or solutions of PS in CH, as compared with the opposite procedure. By means of phase equilibrium experiments tie lines and the critical curve could also be constructed. For a theoretical calculation of the latter from information concerning the binary sub‐systems (e.g. light scattering of PS in DMF) the single liquid approximation was applied to DMF/PS instead of—with respect to miscibility—the more dissimilar DMF/CH; the results are in qualitative accord with experimental observations. Orienting measurements concering the chain length dependence of the partition coefficient in co‐nonsolvent systems indicate that their aptitude for fractionation is considerably worse than that of normal systems under comparable conditions.
Free radicals in colloidal systems: Formation and decay of radicals in the tensides α‐hexadecyl‐ω‐hydroxypoly(oxyethylene) and α‐tetradecyl‐ω‐(sodium sulfonato)tri(oxyethylene)
Authors: Henglein A. , Proske Th. 
Published: April 2003

AbstractOrganic radicals were produced in the tensides C16H33(OCH2CH2)21OH and C14H29(OCH2CH2)3‐SO3Na in aqueous solutions using a short pulse of high energy electrons. The radicals were formed by OH attack on the (OCH2CH2)x‐parts of the tensides. The decay of the 250nm absorption of the radicals was recorded at different initial radical concentrations and tenside concentrations. Several radicals could be produced in one micelle. Radicals formed in the same micelle decay within microseconds or faster. The half life time τ1 in a micelle carrying two radicals is 2,0·10−6 s for C16H33(OCH2CH2)21 OH and less than 6·10−7 s for C14H29(OCH2CH2)3SO3Na. A model for intramicellar radical‐radical reactions is proposed according to which the rate is faster in tensides of high critical micelle concentration. Single radicals in micelles of C16H33(OCH2CH2)21OH can deactivate each other without leaving the micelles. This intermicellar reaction is discussed in terms of the rate of diffusion‐controlled micelle‐micelle encounters, an encounter time of 7·10−8s, and the above time τ1 for intramicellar reaction. The observed rate constant 2k of intermicellar reaction is 3,5·106 mol−1·l·s−1. At low tenside concentrations, the bimolecular rate constant increases since more single tenside radicals are present in solution. They react rapidly (ca. 108 mol−1·l·s−1) with radicals in micelles. Single radicals in C14H33(OCH2CH2)3‐SO3Na micelles cannot directly react with each other because of the Coulombic repulsion between two anionic micelles. Reaction occurs after the exit of a tenside radical from its micelle, the rate of which depends on the micellar equilibrium Mn⇄Mn−1+M (M: tenside molecule; n: agglomeration number of micelle). A single radical in solution reacts with a single radical in a micelle with 2k = 1,0·108 mol−1·l·s−1 and with another single radical in solution with 4,0·107 mol−1·l·s−1.γ‐Irradiation of both tensides in aqueous solution leads to slight increases in viscosity, followed by turbidity beyond the “gel dose” and phase separation. These effects are explained in terms of crosslinking of tenside molecules. Formation of a large network requires bridges between all participating tenside molecules (not only bridges between micelles).
Effect of pressure on the termination rate constant in free radical polymerization. Correlation between rate constant and monomer viscosity
Authors: Ogo Yoshiaki , Kyotani Takashi 
Published: April 2003

AbstractViscosities of six kinds of monomers—styrene, methyl methacrylate, butyl methacrylate, butyl acrylate, vinyl acetate, and octyl methacrylate—were measured under high pressures up to 1000 bar at 30°C. The pressure dependences of the viscosities could be well expressed by an exponential function and correlated with the effect of the termination rate constant determined previously. Therefore, the termination constants at various pressures can be predicted by the evaluation of the pressure dependence of the viscosity of the corresponding monomer. The applicability of O'Driscoll's termination theory under high pressure is also discussed.
Elektrokinetische untersuchungen an fasern, 5. Ableitung einer strömungsstromgleichung für ein stabbündelfeld
Authors: Aichele Wilfried , Schollmeyer Eckhard 
Published: April 2003

AbstractAn equation is derived to relate the streaming current of an arrangement of cylinders parallel to a streaming fluid with the zeta‐potential of the solid‐liquid interface. The derivation is in analogy to the principles used by Smoluchowski to calculate the streaming current of a single capillary, i.e. a laminar streaming fluid and the applicability of Poisson's equation. It is shown that both equations are identical.
Equivalent hydrodynamic sphere models for viscosity, sedimentation, and diffusion
Authors: Mahabadi Hadi Kh. , Rudin Alfred 
Published: April 2003

AbstractAvailable data for intrinsic viscosity, molecular weight and infinite dilution frictional properties of polymer‐solvent systems are used to establish the relation between the radius, rf, of a “frictional” equivalent sphere applicable to sedimentation and diffusion phenomena, and the radius, rη, of the “viscosity” hydrodynamic sphere. It is found that the experimental data agree with a common equivalent hydrodynamic sphere model in which rη = rf.
15N NMR spectroscopy, 13. Copolymerization of glycine‐N‐carboxyanhydride and β‐alanine‐N‐carboxyanhydride
Authors: Kricheldorf Hans R. 
Published: April 2003

AbstractIn contrast to 13C NMR spectra, 15N NMR spectra allow one to characterize the sequence of copolypeptides built up by glycyl and β‐alanyl residues, because the shifts of the Gly‐Gly, β‐Ala‐Gly, Gly‐β‐Ala, and β‐Ala‐β‐Ala bonds differ from each other by several p.p.m. Hence, the copolymerization of glycine‐NCA and β‐Alanine‐NCA can be investigated by quantitative evaluation of the 15N NMR spectra obtained from the resulting copolymers. The copolymerization of these two amino acid NCAs initiated by primary amines leads to random sequences; the copolymerization is azeotropic in nature, and both copolymerization reactivity ratio parameters are near 1. If aprotic bases like pyridine and triethylamine are used as catalysts, the rate of incorporation of glycine is higher than that of β‐alanine and the copolymers possess a block structure.
Diffusion rayleigh dans le rouge par les solutions de polymères. Application à quelques problèmes
Authors: Millaud Bernard , Strazielle Claude 
Published: April 2003

AbstractThis paper describes how a classical light scattering apparatus (FICA 42000) can be modified in order to allow measurements with red light using a gas laser. This apparatus is calibrated, and experimental results are compared with the theoretical results. The advantages of such measurements are that, when red light is used, one has no fluorescence problems, and the properties of the laser (i.e., collimation, stability and illumination) allow the possibility of simultaneous measurements of both gel permeation chromatography (GPC) and light scattering.
Peroxo salts as initiators of vinyl polymerization, 1. Effect of Ag(I) and Cu(II) on the polymerization of acrylamide initiated by peroxodisulfate ions
Authors: Singh Ulagaraj Chandra , Manickam Subramania pillai P. , Venkatarao Krishnarao 
Published: April 2003

AbstractThe kinetics of polymerization of acrylamide initiated by potassium peroxodisulfate, in the presence and absence of Ag(I) and Cu(II) ions, was studied. The rate law for the polymerization was established. Cu(II) ions were found to reduce both the rate and degree of polymerization.
Polymerization of N‐vinylcarbazole, 3. Studies of copolymerizations with methyl methacrylate and styrene
Authors: Bevington J. C. , Dyball C. J. , Leech J. 
Published: April 2003

AbstractCopolymers of N‐vinylcarbazole (VCZ) with methyl methacrylate (MMA) and styrene (ST) were prepared using doubly‐labelled benzoyl peroxide as initiator and the relative numbers of benzoyloxy and phenyl end‐groups were determined. In the copolymers containing MMA, the ratios of the two types of end‐group are those expected for products of free radical polymerization. The copolymers of VCZ with ST contain benzoyloxy and phenyl end‐groups in proportions which correspond to those found in homopolymers of VCZ made in non‐radical polymerizations promoted by the peroxide.
Metalation of polystyrene and its model compound 1,3,6,8‐tetraphenyloctane by the sec‐butyllithium‐N,N,N′,N′‐tetramethylethylenediamine complex
Authors: Clouet Gilbert , Brossas Jean 
Published: April 2003

Abstract1,3,6,8‐Tetraphenyloctane (1) the tetramer of styrene was metalated by a complex of sec‐butyllithium with N,N,N′,N′‐tetramethylethylenediamine in cyclohexane. The lithiated styrene tetramer was quenched with deuterium oxide, and the deuterated compounds were examined by mass, 1H NMR and IR spectrometry. The spectroscopic data revealed that the lithium atoms are placed chiefly at the aromatic ring. The meta/para distribution of metalated sites in the aromatic ring was found to be approximately 2:1. Polystyrene was lithiated with the same complex. The amount of lithium in the polymer could be varied over a wide range. It was found that each lithium atom in the polymer can be substituted by a functional group, thus permitting the introduction of a controlled number of functional groups. By use of this metalation technique, phosphonate groups could be introduced into the aromatic rings of polystyrene.
Isoprene dimerization
Authors: Clouet Francoise , Brossas Jean 
Published: April 2003

AbstractThe mixture of isomeric dimers obtained by the dimerization of isoprene, was analyzed. The study of dimer structures obtained after deactivation of the dianionic dimers by addition of a suitable reagent, revealed the nature of the intermediate and the weight of mesomeric forms of the initial radical anion in the case of an electron transfer initiation.
Synthesis and study of poly(oxine‐methylene)s
Authors: Patel B. S. , Patel S. R. 
Published: April 2003

AbstractThe work presented in this paper comprises synthesis and study of poly(oxine‐methylene)sSystematic name: poly(8‐hydroxyquinolinediylmethylene)s.
. The synthesis is based on Friedel‐Crafts polyalkylation of 8‐quinolinol, commonly known as oxine, with dichloromethane in presence of anhydrous aluminium trichloride. Five polymer samples are prepared by varying molar proportions of the two monomers. The polymer samples are insoluble in commonly used organic solvents. They are soluble in acetic acid, formic acid, and in conc. sulfuric acid. The IR and UV spectral characteristics of the polymer samples are reported. Molecular weight of the polymer samples is estimated by conductometric titration in pyridine against standard sodium methoxide. Viscometric study is carried out both in formic acid and glacial acetic acid at 35°C. Solutions of polymer samples in formic acid show normal behaviour and those in glacial acetic acid show abnormal behaviour. Various empirical relations are applied to correlate these data in glacial acetic acid. Acetic acid containing water and simple electrolytes is used as a medium to suppress abnormal behaviour. The thermal properties of the polymer samples are also studied. All the results of analysis are adequately correlated. One oxine‐formaldehyde polymer sample was also synthesized for comparison.
Die Struktur kollagenähnlicher Homo‐ und Heteropolytripeptide, 4. Polytripeptide durch repetitive Peptidsynthese und Verbrückung von Oligopeptiden
Authors: Roth Werner , Heppenheimer Kurt , Heidemann Eckhart R. 
Published: April 2003

AbstractCollagen‐ like oligopeptides of defined chain length were synthesized via the following tripeptides which were combined stepwise: Boc‐Gly‐L‐Pro‐L‐Pro‐OH (1), Boc‐Gly‐L‐Pro‐L‐Lys‐OH (2), Boc‐L‐Ala‐Gly‐L‐Pro‐OH (4), Boc‐Gly‐L‐Pro‐L‐Leu‐OH (6), and Boc‐L‐Ala‐L‐Hyp(OBz)‐Gly‐OH (9). Two methods for covalent bridging of three oligopeptides of the same sequence were applied resulting in the formation of polypeptides of type 22 or 23.
Infrared spectroscopic studies on polyethylene, 5. The measurement of chain branching on powder polyethylene specimens
Authors: Baker Clive , David Peter , Maddams William F. 
Published: April 2003

AbstractThe scope and limitations of the potassium bromide disc technique for the infra‐red determination of chain branching in small samples of polyethylene in powder form have been assessed. Many of the samples encountered have an average particle size, prior to grinding with potassium bromide, of about 100 μm and very satisfactory results have been obtained, but the presence of larger particles leads to poor quality discs and inferior results. The well established double beam technique proves suitable for removing the interfering methylene absorption and compensation with polymethylene in the form of a film rather than as a pressed disc is preferable. Difficulties were encountered in preparing branching standards in a uniform and fine powder form, to avoid variation of the absorption coefficient of the 1 378 cm−1 methyl band with particle size. Such powders are best obtained by precipitation from solution rather than by low temperature milling. Despite these problems chain branching measurements may be made with a precision of between 5 and 10% and an accuracy of about 15%.
Glass transition temperature of linear saturated and unsaturated polyesters
Authors: Cecere Giuseppe , de Candia Francesco , Palumbo Rosario 
Published: April 2003

AbstractIn the present paper we have investigated the role that the presence of trans double bonds plays on the glass transition temperature of linear polyesters. Experimental data indicate that the glass transition temperature is increased by an increase of the unsaturation concentration. The effect is not drastic but it is well detectable. This result is discussed taking into account the chain microstructure and the bulk structure effects.