bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spectroscopic measurements on spontaneously polymerizing styrene, 2. The estimation of the reactivity of the two Diels‐Alder‐isomers towards polymer radicals
Authors: Olaj Oskar Friedrich , Kauffmann Harald Friedrich , Breitenbach Johann Wolfgang 
Published: April 2003

AbstractSpectroscopic measurements at 335 nm on polymerizing styrene have been carried out with spontaneously polymerizing as well as dibenzoyl peroxide (BPO)‐initiated bulk systems. The evidence for the formation of two Diels‐Alder‐intermediates, 1a and 1b, out of which only 1a seems to be capable to produce initiating radicals by reaction with the monomer, can also be derived from the development of the absorption, characteristic for the intermediates, during the BPO‐initiated polymerization. From the dependence of the overall rate constants of consumption of 1a, k2,a[M], and 1b, k2,b[M], on the rate of polymerization the reactivity of 1a and 1b towards polymer radicals can be estimated. Whereas 1b, the less reactive intermediate, seems to be mainly consumed by polymer radicals through copolymerization, chain transfer being unimportant, (the rate constant of consumption of 1b by polymer radicals, k3,b, relative to the constant of chain propagation kp ranges from 2,1 at 60°C to 3,2 at 80°C) the corresponding ratio for 1a, k3,a/kp, which goes from 113 at 80°C to 143 at 60°C, is supposed to represent primarily the constant of chain transfer of 1a in styrene polymerization. Under the condition of spontaneous polymerization the reaction with polymer radicals contributes 16% (for 1a) and 5–8,5%, depending on temperature (for 1b), to the overall rate of consumption of the intermediates. The stationary concentration of 1a, the isomer which accordingly is solely responsible for initiation as well as chain transfer in spontaneous styrene polymerization, is calculated to range from 5,2·10−6 mol l−1 at 60°C to 8,5·10−6 mol l−1 at 80°C.
Herstellung und antivirale Wirksamkeit von Polyacrylsäure und Polymethacrylsäure
Authors: Mück Karl‐Friedrich , Rolly Heinrich , Burg Karlheinz 
Published: April 2003

AbstractThe antiviral activity of a number of fractions of poly(acrylic acid)s and poly(methacrylic acid)s with different tacticities, different molecular weights and molecular weight distributions has been investigated. Isotactic poly(acrylic acid)s are essentially more antiviral active in the whole area of efficacy than the atactic ones. Independent of the tacticity poly(acrylic acid)s with molecular weights smaller than 5000 show no significant effects, polymers with molecular weights greater than 25000 are toxic in the used doses. The optimum of efficacy is between 6000 and 15000. Isotactic poly(acrylic acid)s with narrow molecular weight distributions are more active than those with broad distributions. The atactic poly(acrylic acid)s with lower efficacy do not show this relationship. Atactic poly(methacrylic acid)s are not antiviral active in vivo compared with untreated controls. Isotactic ones have a just detectable efficacy which is essentially lower than the activity of the atactic poly(acrylic acid)s.
Zur Bestimmung der Statistik der konstitutiven und konfigurativen Monomerverknüpfung in Polyolefinen durch NMR‐Spektroskopie
Authors: Elgert Karl‐Friedrich , Ritter Wolfgang 
Published: April 2003

AbstractA simple statistical treatment of the constitutional and configurational monomer enchainment of substituted olefins for use in NMR spectroscopy is given.
Ultracentrifuge study of critically branched polycondensates, 4. Hinge point analysis and higher average molecular weights
Authors: Leonis Constantine G. , Suzuki Hidematsu , Gordon Manfred 
Published: April 2003

AbstractModel polycondensates of 1,10‐decanediol and 1,3,5‐benzenetriacetic acid stabilised by means of diazodiphenylmethane and ketene are utilised to extend further our understanding of the critically branched state and to investigate possible contributions of the ultracentrifuge to the study of highly polydisperse macromolecules in non‐ideal, dilute solutions. By way of computerised curve fitting, the concentration gradient curve is obtained from its concentration profile in the ultracentrifuge cell. From this the weight average molecular weight M̄1 is calculated by the hinge point method. It is also confirmed that values of the two next higher moments of the molecular weight distribution, viz. M̄2/1 and M̄3/2 (i.e. Mz and Mz+1) can hardly be distinguished from infinity for these samples. Application of the hinge point method to systems of high polydispersity is found both theoretically and experimentally to furnish M̄1 after a dual extrapolation of the measured M̄ against the generalised speed parameter λ and the initial concentration c0. It is found theoretically that for estimation of the higher molecular weight moments, plots of M̄ M̄ and M̄ M̄ M̄ (not merely M̄ and M̄) must be extrapolated against the same variables, i.e. λ and c0. The quantitative results thus obtained are discussed in the context of previous results on these materials. They are compared with the classical theory for random f‐functional polycondensates and statistical cut‐off effects on the high molecular weight tail of distribution are assessed.
Synthese und eigenschaften einiger höhergliedriger cyclischer ätheracetale
Authors: Albrecht K. , Fleischer D. , Rentsch C. , Yamaguchi H. , Schulz R. C. 
Published: April 2003

AbstractOptimized syntheses of 1,3,6,9‐tetraoxacycloundecane (2), 1,3,6,9,12‐pentaoxacylotetradecane (3), and 1,3,6,9,12,14,17,20‐octaoxacyclodocosane (4) as well as some physical and chemical properties and the proof of structure are reported.
Polymere aus Nitrilen, 6. Anionische Polymerisation von Fumaronitril. Isomerisierung von Fumaronitril zu Maleonitril
Authors: Helling Günter , Wöhrle Dieter 
Published: April 2003

AbstractThe oligomer of fumaronitrile 3, obtained by anionic polymerisation of fumaronitrile with butyllithium, is able to isomerise fumaronitrile to maleonitril. Kinetics and thermodynamics are examined and a model for the mechanism is proposed.
Crystallization of polypeptides in the course of polymerization, 7. Crystallization of poly(γ‐methyl‐L‐glutamate), poly(γ‐benzyl‐L‐glutamate) and poly(β‐benzyl‐L‐aspartate)
Authors: Kōmoto Tadashi , Kim Kea Yong , Kawai Tohru 
Published: April 2003

AbstractHeterogeneous polymerizations of γ‐methyl‐L‐glutamate N‐carboxy anhydride (NCA), γ‐benzyl‐L‐glutmate NCA, and β‐benzyl‐L‐aspartate NCA were carried out using butylamine as initiator in acetonitrile at 30°C. The oligomer chains formed in the beginning of the polymerization crystallized into the antiparallel β‐form and thereafter the α‐helical chains grew from the active sites of the β‐chains. The polymerization of γ‐methyl‐L‐gultamate NCA proceeded to 100% conversion and accordingly gave rise to high molecular weight poly(γ‐methyl‐L‐glutamate). The polymerizations of γ‐benzyl‐L‐glutamate NCA and β‐benzyl‐L‐aspartate NCA stopped at 54% and 16%, resp. The levelling‐off of the conversion at such low values, in spite of the α‐helical chain growth, may be due to the occlusion of the active chain ends of the resultant poly(γ‐benzyl‐L‐glutamate) and poly(β‐benzyl‐L‐aspartate) into the crystals. It was concluded that the interlamellar crystallization was induced by the intermolecular interaction between the benzyl groups of the polymer side chains, giving rise to the occlusion of the active growing chain ends into the interstices of the crystal formed during the polymerization.
Bestimmung der geschwindigkeitskonstanten und der effektivitäten beim zerfall von 2,2′‐azoisobutyronitril in styrol, N‐vinyl‐2‐pyrrolidon und methylmethacrylat
Authors: Braun Dietrich , Quella Ferdinand 
Published: April 2003

AbstractThe decomposition rate constants kd of initiators can be determined by a new method directly in monomers as solvents. If a suitable inhibitor is added to a monomer mixture with the initiator the latter decomposes nearly without monomer conversion. The initiator concentration—after the inhibitor is consumed—can be found by means of the dilatometrically determined polymerization rate after the induction period. The functional connection between polymerization rate and initiator concentration found without inhibitor is used as a calibration curve for that purpose.The dilatometrical measurements were made in the monomers styrene and N‐vinyl‐2‐pyrrolidone using 2,2′‐azoisobutyronitrile (AIBN) as initiator and p‐quinone as inhibitor. The following decomposition rate constants were found: kd=1,52 · 10−5 S−1 (styrene) and kd=1,62 · 10−5 S−1 (N‐vinyl‐2‐pyrrolidone), which is in agreement with literature values.Initiator efficiencies f were calculated: f=0,46 (styrene), f=0,47 (N‐vinyl‐2‐pyrrolidone). In methyl methacrylate (MMA) 2,2′‐diphenyl‐1‐picrylhydrazyl (DPPH) was used as inhibitor. Under certain conditions the product kdf can be calculated from the consumption rate of DPPH. The value found in MMA (kdf=3,7 · 10−6 s−1) is lower than that reported in literature (6,45 · 10−6 s−1).
Second virial coefficient of three‐block copolymers
Authors: Sikora A. 
Published: April 2003

AbstractThe two leading terms in the perturbation series expansion of the second virial coefficient A2 have been derived for a three‐block copolymer. The theoretical dependences of second virial coefficients on composition of a two‐block copolymers AB, b three‐block copolymers ABA and c mixtures of two homopolymers A and B have been compared at low values of the excluded volume parameters zA, zB and zAB. It follows from these calculations that with increasing thermodynamic quality of the solvent (with respect to both homopolymers) the effect of repulsive interaction between unlike segments of types A and B on the second virial coefficient of the copolymer decreases. The applicability of perturbation series to block copolymers is discussed.
Investigations on the mechanism of radiation induced crosslinking in ethylene‐propylene‐diene terpolymers
Authors: Geissler Wolfgang , Zott Hansjörg , Heusinger Helmut 
Published: April 2003

AbstractThe radiation induced crosslinking, double bond consumption, and radical formation of ethylene‐propylene‐copolymers (EPM) and ethylene‐propylene‐diene terpolymers (EPDM), containing either 5‐ethylidene‐2‐norbornene or dicyclopentadiene as the diene component, were investigated. The diene content was found to increase crosslinking as well as chain scission, 5‐ethylidene‐2‐norbornene being more efficient than dicyclopentadiene. The ESR‐spectra of EPM and EPDM at −196°C are almost identical, showing alkyl radicals corresponding to the ethylene and propylene component. At −50°C in EPDM allyl type radicals characteristic of 5‐ethylidene‐2‐norbornene, 6, and dicyclopentadiene residues, 4, are detected. Based on the results a mechanism for radiation induced crosslinking in EPDM is proposed.
Coupling reactions between polystyrene containing acyl chloride endgroups and poly(vinyl acetate) containing amino groups at the chain end or along the chain
Authors: Ikada Yoshito , Maejima Kazuo , Iwata Hiroo 
Published: April 2003

AbstractPolystyrene (PS) and Poly(vinyl acetate) (PVAc), both carrying one terminal acyl chloride group, were synthesized by radiation‐polymerization in the presence of trichloroacetyl chloride, a chain transfer agent, and the acyl chloride groups of PVAc were converted to amino groups by reacting with excess ethylenediamine. Partial acetalization of poly(vinyl alcohol) with aminoacetaldehyde followed by acetalation of the remaining hydroxyl groups in the polymer yielded PVAc having a number of pendant amino groups distributed along the main chain. Condensation coupling reactions between the acyl chloride and amino groups were carried out in chloroform at room temperature to yield PS‐PVAc diblock copolymers and PVAc‐PS graft copolymers with many branches of PS. The pure copolymers were isolated from the reaction products by extraction and then characterized by determining chemical compositions and number‐average molecular weights.
Synthesis of Nε,N′ε‐(pyromellitoyl)dilysine and its copper (II) chelate polymer
Authors: Yang Chin‐Ping , Lin Tzu Fang , Iwakura Yoshio 
Published: April 2003

AbstractSynthesis of Nε,N′ε‐(pyromellitoyl)dilysine (8) was carried out by reacting L‐lysine with dimethyl pyromellitate (6) followed by thermal imidation. The obtained product 8 was reacted with Cu2+ ions to form a light blue chelate polymer (9). Model compounds, Nε‐phthaloyllysine (4) and its copper chelate complex 5, were also synthesized by a similar process for comparison. IR spectra, optical and solubility properties of the monomer and its chelate polymer together with their corresponding model compounds were investigated. The thermal stability of chelate polymer 9 in acid solution of different pH value were also investigated.
Optimization of solution fractionation of poly(vinyl acetate)
Authors: Klein Joachim , Werner Michael 
Published: April 2003

AbstractThe theoretical assumptions to understand the elution mechanism of the discontinuous solution fractionation and complete elution method could be confirmed for the system poly(vinyl acetate)/butyl acetate/cyclohexane. In this case the process of complete elution, however, can only be carried out with an unfavorable high consumption of time and material. The complete elution method with all its advantages can be preserved, if the process is carried out as multistage process with a limited number of discontinuous steps. By means of such a multistage procedure improved separation results were achieved compared with the conventional single stage procedure. Furthermore some results are given which show a decrease of the separation effect of solution fractionation due to procedural limitations.
Kinetik von Copolymerisationen, 2. Dilatometrische untersuchungen der Copolymerisationen von N‐vinyl‐2‐pyrrolidon, Styrol und Methylmethacrylat
Authors: Braun Dietrich , Disselhoff Gabriele , Quella Ferdinand 
Published: April 2003

AbstractThe copolymerizations of N‐vinyl‐2‐pyrrolidone/styrene and N‐vinyl‐2‐pyrrolidone/methyl methacrylate—both systems with extremely different reactivity ratios—have been investigated in a recording dilatometer equipped with a thermo‐couple. The shrinkages of the systems can be described by the theory of Wittmer. The necessary values for the homopolymerizations as well as the binary reactivity ratios have been determined. The shrinkages have been verified independently by density measurements.
The effect of externally applid stresses on the structure of an ethylene‐rich EPDM terpolymer
Authors: Preedy John E. , Wallis Susan , Wheeler Ernest J. 
Published: April 2003

AbstractStructural changes in an ethylene‐rich ethylene‐propylene‐diene terpolymer (EPDM) were studied as a function of applied external stress. From its initial unstretched value of 15%, the terpolymer crystallinity increased to 73% at a tensile strain of 225%. X‐ray diffraction patterns showed that, when stretched, the terpolymer assumed a hexagonal structure and an increase in the until cell a‐dimension occurred. A fibre texture developed with the lamellae inclined to the tensile axis.
Melting temperatures and enthalpies of polyethers: Poly(hexamethylene oxide)
Authors: Marco Carlos , Bello Antonio , Fatou José Gomez 
Published: April 2003

AbstractAn experimental study is reported of the dependence of the melting temperature Tm on the crystallization temperature Tc for molecular weight fractions of poly(hexamethylene oxide) in the range from Mn=2260 to Mn=35 500, with attention to the level of crystallinity.It has been found that for the highest molecular weight fraction, at low levels of crystallinity, the extrapolated linear relation Tm vs. Tc yields an equilibrium melting temperature of 346,5K in very good accord with theoretical expectations. Moreover, the behaviour and theory for low‐molecular‐weight fractions is analyzed.The enthalpy of fusion for poly(hexamethylene oxide) has been determined from two kinds of experiments: by measuring calorimetrically the apparent heat of fusion at different levels of crystallinity, and by using the polymer‐diluent method in decahydronaphthalene and 1,2,3,4‐tetrahydronaphthalene. The enthalpy of fusion was found to be 54–57 cal/g (=226–238J/g).
Strukturaufklärung der bei der Addition von 2‐Cyano‐2‐propylradikalen anp‐Tolyl‐ und 4‐Cyclohexylphenyl‐methacrylat entstehenden Produkte mittels1H NMR‐ und Massenspektren
Authors: Kämmerer Hermann , Pachta Jiri , Ullner Helmut 
Published: April 2003

AbstractThe chromatographically pure products, gained on the suppression of polymerisation ofp‐tolyl or 4‐cyclohexylphenyl methacrylates (1, 2) by a great excess of 2‐cyano‐2‐propyl radicals, could be isolated in a total yield of 95 to 100%. The structure of these products was established by1H NMR and mass spectroscopy. There arep‐tolyl or 4‐cyclohexylphenyl 4‐cyano‐2‐(2‐cyano‐2‐propyl)‐2,4‐dimethylvalerate (1a, 2a),p‐tolyl or 4‐cyclohexylphenyl 2‐(2‐cyano‐2‐methylpropyl)acrylate (1b, 2b),p‐tolyl or 4‐cyclohexylphenyl 4‐cyano‐4‐methyl‐2‐(2‐cyano‐2‐methylpropyl)valerate (1c, 2c),p‐tolyl or 4‐cyclohexylphenyl 4‐cyano‐2,4‐dimethylvalerate (1d, 2d), andp‐tolyl or 4‐cyclohexylphenyl 4‐cyano‐2,4‐dimethyl‐2‐pentenoate (1e, 2e(2f)). It is possible to give a scheme of reactions on the suppression of the radical polymerisation.
Photogalvanic effect of thin‐layer photocells composed of thionin‐polymer/Fe(II) systems
Authors: Shigehara Kiyotaka , Sano Hiroshi , Tsuchida Eishun 
Published: April 2003

AbstractTwo types of thionin (Th)‐polymers were prepared and their characteristics in the photogalvanic effects were studied by the use of thin‐layer photocells. One type of the polymers being soluble in methanol was somewhat cross‐linked by Th nuclei, and was cast on a water containing (Fe(II) solution) membrane between SnO2 and Pt electrodes. This membrane type thin‐layer photocell generated larger photo‐induced electricity than the similar thin‐layer photocell composed of the corresponding monomeric Th/Fe(II) solution, the reason of which was considered to be due to the electrostatic effect of cationic sites incorporated into the polymers. Another type of polymers was used as water‐containing (Fe(II) solution) gels, and the thin‐layer photocells composed of them generated a very small photo‐induced electricity due to the strong steric hindrance of entangled strands, which should decrease the possibility of the electrode reaction.
Cyclic oligomers in the cationic polymerization of 3,3‐dimethyloxetane
Authors: Bucquoye Marc , Goethals Eric J. 
Published: April 2003

AbstractThe formation of cyclic oligomers in the cationic polymerization of 3,3‐dimethyloxetane (1) was investigated. By means of gas chromatography coupled with mass spectroscopy, cyclic oligomers from tetramer up to nonamer (2a–f) were detected in decreasing concentration. The oligomer/polymer ratio at complete monomer consumption changes with the initiating system used. This ratio is not influenced by the initiator concentration but it increases with decreasing monomer concentration. It is proposed that the cyclic oligomers are formed by reaction of the monomer with macrocyclic oxonium ions of type 5 which in turn are formed by an intramolecular (temporary) termination reaction. The high preference to form cyclic tetramer is discussed in terms of the preferred polymer backbone conformation. In the polymerization of oxetane, cyclic tetramer is the most important oligomer, but, contrarily with previous reports, higher oligomers were also found to be present.
The formation of poly(phenylene sulfide)s and the substituent effect in reactions of substituted chlorobenzenes with sulfur
Authors: Hortling Bo , Lindberg J. Johan 
Published: April 2003

AbstractThe reactions of six substituted chlorobenzenes with sulfur were investigated, and the results were compared with the results of earlier investigations in which sodium carbonate also took part in the reactions. The effect of the amount of chlorine and of the different substituents on the reaction mechanism is discussed. The approximate structures of the cross‐linked substituted poly(phenylene sulfide)s are also given.
Additive effect of poly(ethylene oxide), 2. An acceleration effect of poly(ethylene oxide) in a williamson reaction
Authors: Hirao Akira , Nakahama Seiichi , Takahashi Mitsuru , Yamazaki Noboru 
Published: April 2003

AbstractThe additive effect of poly(ethylene oxide) (PEO) in the Williamson reaction between sodium phenolate and butyl bromide was investigated. Under certain conditions a remarkable rate acceleration by PEO was observed in this reaction, which is explained by the fact that a cooperative coordination of oxygen atoms of PEO with metal cations promotes ion dissociation. The relationship between the formation of a PEO‐sodium phenolate complex and the reaction rate, and also the dependency of the reaction rate on the molecular weight of PEO were examined.
Über die copolymerisation von (3‐vinylphenylazo)‐methylmalonodinitril mit styrol 7. Mitteilung über azo‐initiatoren
Authors: Kerber Robert , Nuyken Oskar , Dorn Maximilian 
Published: April 2003

Abstract(3‐Vinylphenylazo)‐methylmalonodinitrile (2) was copolymerized with styrene up to high conversion giving no remarkable change in the monomer composition. The reactions were carried out in emulsion at 5°C, in bulk at 50°C, and in solution at 60°C. The azo compound displays not only the properties of an initiator (thermolysis) and monomer (vinyl group), but also the behaviour of a retardation reagent (azo‐function) explaining the decrease of polymerization rates and of molecular weights with increasing amounts of azo compound.
Tetraaza[14]annulen‐derivate und ihre vorstufen, 3. Katalyse, halbleitereigenschaften und thermostabilität der metallkomplexe
Authors: Müller Reinhardt , Wöhrle Dieter 
Published: April 2003

AbstractThe use of low molecular weight, bicyclic, and polymeric tetraaza[14]annulene metal complexes 1–5 of copper(II), cobalt(II), iron(II), and nickel(II) as oxygen activating catalysts in the oxidation of ethylbenzene to acetophenone was examined. In addition semiconducting properties and thermal stabilities of these complexes were investigated.
An automatically controlled reaction vessel suitable for the kinetic investigation of polymerization processes with half life periods of 2 seconds and greater
Authors: Warzelhan V. , Löhr G. , Höcker H. , Schulz G. V. 
Published: April 2003

AbstractA reaction vessel automatically controlled by magnetic valves is described which allows kinetic measurements of reactions with half lives t1/2≥2s by gravimetric determination of the conversion. Thus, it covers the gap between the flow tube and the conventional reaction vessel.The influence of mixing time and filling time on the molecular weight distribution of an anionically prepared polymer is discussed.