bluuebunny/crossref_metadata_2025_split huggingface dataset:
Versuche zur darstellung von azo‐polymeren durch photochemische polykondensation
Authors: Bössler Hanns Henning , Schulz Rolf C. 
Published: April 2003

AbstractEs wurde versucht, die Photolyse von aromatischen Aziden zur Darstellung von Polymeren auszunutzen. Zu diesem Zweck wurden mehrere Bis‐Azide hergestellt und in verschiedenen Lösungsmitteln bestrahlt, wobei die berechnete Menge Stickstoff abgespalten wurde. Die meisten der tiefgefärbten Bestrahlungsprodukte sind unlöslich; bei bestimmten Ausgangsverbindungen konnten in Dichloressigsäure lösliche Anteile erhalten werden. Auf die Struktur der Bestrahlungsprodukte kann durch Vergleich der Spektren dieser Lösungen mit denen einer Modellverbindung geschlossen werden.
Über synthese und reaktionen mono‐und difunktioneller thiocarbonsäure‐trimethylsilylester
Authors: Kricheldorf Hans Rytger , Leppert Elmar 
Published: April 2003

AbstractDurch Umsetzung von Carbonsäurechloriden oder ‐anhydriden mit Hexamethyldisilthian lassen sich Thiocarbonsäure‐trimethylsilylester (I und II) herstellen. Die Silylester I und II reagieren mit verschiedenen elektrophilen Reagenzien, z B. mit Säurechloriden und Alkylbromiden unter Eliminierung von Halogensilan, wobei stets Thiocarbonsäure‐S‐acyl‐oder ‐S‐alkylderivate entstehen. Aus α.ω‐Dithiocarbonsäure‐trimethylsilylestern (II) und den zugehörigen Dicarbonsäurechloriden wurden bisher noch nicht beschriebene Polyacylsulfide gewonnen; bei der Umsetzung mit Piperazin‐bis‐carbonylchlorid entstehen Polyamide (s. Summary).
Comparison of some statistic parameters of the most probable and the tung distributions with respect to the molecular heterogeneity
Authors: Sibiński Henryk 
Published: April 2003

AbstractSome important parameters of the most probable and the TUNG distributions with respect to the molecular heterogeneity have been compared. Furthermore an interpretation method of the fractionation data has been given allowing to decide relatively simply and quickly whether the tested distribution is either of the most probable or the TUNG type.
Polymere aus Nitrilen. II. Einige Polykondensationsreaktionen des 2.5‐Diimino‐pyrrolidins, Imino‐pyrrolidons, Succinimids, 5‐Chlor‐2‐imino‐1‐pyrrolins und Bernsteinsäuredinitrils
Authors: Wöhrle D. 
Published: April 2003

AbstractErhitzen von 2.5‐Diimino‐pyrrolidin, Imino‐pyrrolidon oder 5‐Chlor‐2‐imino‐1‐pyrrolin in Substanz oder in hochsiedenden Lösungsmitteln führt in einer Polyselbstkondensation zum dunkel gefärbten Poly(1‐pyrrolin‐2‐yl‐5‐ylidennitrilo). Die Umsetzung von Bernsteinsäuredinitril, Succinimid oder 2.5‐Diimino‐pyrrolidin mit aromatischen Diaminen wie z. B. p‐Phenylendiamin ergibt in einer Polykondensationsreaktion dunkel gefärbte Polymere. Halbleitereigenschaften (σ300°K ∼10−8 bis 10−15 Ω−1cm−1) und thermische Analysen werden beschrieben.
Radiolysis of polymethylmethacrylate in the presence of ethylmercaptan. II. An ESR investigation
Authors: Geuskens G. , Fuld D. , David C. 
Published: April 2003

AbstractThe ESR spectra of polymethylmethacrylate (PMM) samples irradiated at 77°K in the presence of ethylmercaptan (EM) consist of a signal assigned to radical anions of the additive superimposed on the spectrum obtained with pure PMM. Although the contribution of the radical anions increases with EM concentration, the total radical yield is independent of the presence of the additive (G = 0.70 ± 0.02). On heating the samples C2H5S• radicals are detected. A mechanism is proposed which is consistent with the ESR results and takes into account the protective effect of EM on the radiolysis of PMM.Free radicals decay by steps at successive constant temperatures. The decay curves have been studied at 150°K as a function of the EM concentration and the results have been discussed.
Détermination des propriétés thermodynamiques de quelques systèmes binaires (mélanges de solvants – solution de polymères de bas poids moleculaire) à partir des données de la diffusion de la lumière
Authors: Fechner Barbara Maria , Strazielle Claude 
Published: April 2003

AbstractDans cet article nous avons examiné le problème de la détermination par diffusion de la lumière des fonctions thermodynamiques comme l'énergie libre d'excés, l'entropie d'excés et la chaleur de mélange de quelques systèmes binaires. Les résultats obtenus pour les systèmes benzène‐méthanol, chloroforme‐éthanol et benzène‐hexane sont comparés avec les données calorimétriques.La détermination des fonctions thermodynamiques et du paramètre d'interaction χ a été également réalisée avec des solutions de polyoxyéthylène dans le méthanol: ce système se caractérise par un paramètre χ constant dans un grand domaine de concentration.
Zur Molekulargewichtsabhängigkeit der Parameter des ausgeschlossenen Volumens bei Poly‐α‐methylstyrol
Authors: Biskup U. , Cantow H.‐J. 
Published: April 2003

AbstractEs wurden Lichtstreumessungen an relativ monodispersen Poly‐α‐methylstyrolen in Cyclohexan durchgeführt. Die Molekulargewichte der acht anionisch hergestellten Präparate liegen zwischen 4 · 104 und 4 · 106. Die Taktizität der Proben war mit NMR‐Spektroskopie charakterisiert worden. Es wurden Θ‐Punkte von 30–32°C gefunden. Diese niedrigen Θ‐Temperaturen sind mit einer relativ starken Temperaturabhängigkeit des zweiten Virialkoeffizienten A2 und ungewöhnlich großen Expansionskoeffizienten α des Trägheitsradius verbunden. Wir vermuten, daß dies auf taktische Heterogenitäten innerhalb der Polymerketten zurückzuführen ist.Für ein von BERRY vorgeschlagenes Iterationsverfahren wurde ein Rechenprogramm erstellt, das auf der Gültigkeit der folgenden Gleichung für A2 basiert,

Das Programm errechnet aus der gemessenen Temperaturabhängigkeit von A2 gemäß der zugrunde liegenden Theorie B0 und die entsprechenden theoretischen Werte von A2 und Θ. Die Anwendung dieses Programms zeigt, daß ein solches Verfahren graphischen Methoden überlegen ist. So kann z. B. B0 und Θ auch aus Meßwerten deutlich oberhalb der Θ‐Temperatur bestimmt werden.Die durch einen Vergleich mit Theorien von YAMAKAWA und KURATA ermittelten B0‐Werte unserer Proben nehmen eindeutig mit zunehmendem Molekulargewicht ab. Diese Diskrepanz zur Theorie kann mit Hilfe des Rechenprogramms auch an Meßwerten anderer Autoren nachgewiesen werden.
Vinyl polymerization. 286. Inhibiting effect of 2.2.6.6‐tetramethyl‐4‐oxo‐piperidine‐1‐oxyl in radical polymerization
Authors: Miura Yozo , Masuda Shunji , Kinoshita Masayoshi 
Published: April 2003

AbstractAn extremely stable free radical, 2.2.6.6‐tetramethyl‐4‐oxo‐piperidine‐1‐oxyl (I) effectively inhibits the radical polymerization of styrene and methyl methacrylate initiated by 2.2′‐azobis(2‐methyl‐propionitrile) (azodiisobutyronitrile). The inhibition period, measured by dilatometry, is proportional to the concentration of I. The rate of the initiation reaction, the ratio of the rate constants k/2kt, and the initiator efficiency, which were calculated from the consumption rate of the inhibitor, agree well with the values in the literature. 2.2.6.6‐Tetramethyl‐l‐(l‐methyl‐l‐cyanoethoxy)‐4‐oxo‐piperidine (II) and 2.2.6.6‐tetramethyl‐1‐benzyloxy‐4‐oxo‐piperidine (III), which are analogs of those expected to be formed in the polymerization systems by reactions of initiating or propagating radicals with I, did not effect the inhibition period and the polymerization rate. 2.2.6.6‐Tetramethyl‐l‐hydroxy‐4‐oxo‐piperidine (IV), a potential disproportionation product between I and initiating or propagating free radicals, showed a weak retarding effect.
Micellization of styrene/butadiene/styrene block copolymers in mixed solvents
Authors: Tuzar Zdeněk , Kratochvíal Pavel 
Published: April 2003

AbstractDilute solutions of styrene/butadiene/styrene (SBS) block copolymers of various compositions in selective solvent mixtures are studied by viscometry, equilibrium dialysis, differential refractometry and light scattering. The addition of ethanol as a selective precipitant to a dioxan solution of SBS leads to selective precipitation of butadiene blocks which are kept in solution by solvated styrene blocks. Under the given conditions (temperature, copolymer composition, mixed solvent composition) the forming micelles attain, at a certain copolymer concentration, a stable weight. The results of measurements show that the micelles are very small particles (radius of gyration up to 20nm) of a high weight (up to 15·106); consequently, the average volume fraction of the polymer in the space occupied by a micelle attains unusually large values (up to 0.35).
Viscosities of dilute solutions of poly(isobutyl methacrylate)
Authors: Zafar M. M. , Mahmood R. , Wadood S. A. 
Published: April 2003

AbstractThe intrinsic viscosities of six fractions (M̄n = 11.59·105 to 5.01·105) of poly(isobutyl methacrylate) in seven solvents at temperatures between 25°C and 60°C show the following order: chloroform > benzene > bromobenzene > dioxane > acrylonitrile > acetone > 2‐hydroxymethyltetrahydrofuran. Values of a and k in the expression [η] = k Ma show little variations with temperature in the case of good solvents, whereas these variations are more pronounced in the case of poor solvents. For chloroform, the best solvent, the value of a was found to be 0.78, and for 2‐hydroxymethyltetrahydrofuran at 25°C the value of a is 0.56. The theta temperature for 2‐hydroxymethyltetrahydrofuran is 19.5 ± 0.3°C.
Preparation of polymers containing fragments of N.N′‐tetramethylthiuram disulfide
Authors: Beniska Jozef , Štaudner Emil , Špirk Eugen 
Published: April 2003

AbstractThe preparation of polymethylmethacrylates at 80 and 95°C and of polystyrenes at 95°C using various concentrations of N.N′‐tetramethylthiuram disulfide (I) is described. The sulphur contents, the molecular weights and the UV spectra of the prepared polymers indicate the presence of fragments of I in the polymer chains and the decrease of the molecular weight with increasing concentrations of I. A sample of polystyrene was also examined by mass spectroscopy.
Alternating copolymerization and cyclocodimerization of acrylonitrile and butadiene in the presence of zinc chloride
Authors: Kuran Witold , Pasynkiewicz Stanislaw , Floriańczyk Zbigniew 
Published: April 2003

AbstractThe copolymerization of acrylonitrile (AN) and butadiene (BD) in the presence of zinc chloride was studied in further detail. The reaction yields as 1:1 copolymer of AN and BD together with varying amounts of the AN/BD cyclodimer 4‐cyanocyclohexane. The effects of varying monomer feed composition and molar proportion of ZnCl2/AN on the yield of the copolymer were determined. Further, it was observed, that the addition of free radical initiators and inhibitors markedly influence the course of the reaction. Initiators significantly reduce the polymerization induction period, characteristic of this copolymerization and enhance the yield of copolymer. Inhibitors conversely reduce the formation of copolymer but enhance formation of the cyclocodimer AN/BD.Addition of styrene (ST) to the system BD/AN/ZnCl2 significantly increases the polymerization rate and results in the formation of a terpolymer AN/BD/ST containing 50 mole‐% AN.Based on these results, various aspects of the copolymerization mechanism of AN with BD catalyzed by ZnCl2 are discussed.
Der einfluß benachbarter grundbausteine auf die ammonolyse von essigsäureestern phenolischer mehrkernverbindungen
Authors: Böhmer Volker , Wörsdörfer Klaus 
Published: April 2003

AbstractDie Ammonolyse der Essigsäureester verschiedener phenolischer Zwei‐ und Dreikernverbindungen, die neben Methylphenolbausteinen jeweils einen Nitrophenolbaustein enthalten, wurde untersucht. In allen Fällen wird wie bei einkernigen Nitrophenylestern die Esterbindung im Nitrophenolbaustein ammonolytisch gespalten. Wenn die Bausteine über Methylenbrücken in ortho‐Stellung zu den phenolischen Hydroxylgruppen verknüpft sind, werden jedoch auch die Esterbindungen in den Methylphenolbausteinen gespalten, obwohl die Ester von Methylphenolen und Mehrkernverbindungen, die nur Methylgruppen als Substituenten tragen, unter gleichen Bedingungen durch Ammoniak nicht angegriffen werden. In übereinstimmung mit kinetischen Messungen anderer Autoren wird hierfür ein Mechanismus vorgeschlagen, dessen geschwindigkeitsbestimmender Schritt die Abspaltung eines Protons aus der Zwischenverbindung ist, die durch nucleophilen Angriff des Ammoniaks auf die Estercarbonylgruppe im Methylphenolbaustein entsteht. Diese Abspaltung erfolgt intramolekular unter Einwirkung der Nitrophenolatgruppe des benachbarten Bausteins.
Spectres de résonance paramagnétique électronique des catalyseurs de polymérisation à base de TiCl3. II. Etude théorique
Authors: Kodratoff Y. , Girard Y. , Kibler M. R. , Guyot A. 
Published: April 2003

AbstractLe spectre de résonance paramagnétique électronique d'un échantillon de TiCl3 (Stauffer H) est analysé comme la somme de cinq signaux élémentaires dont trois représentent 85% du total et présentent une symétrie axiale. A l'aide de la théorie du champ cristallin et des résultats d'une étude spectroscopique UV‐visible en réflexion diffuse, on arrive à conclure que ces signaux proviennent de défauts internes de la structure cristalline; cette conclusion est en accord avec plusieurs observations expérimentales.
Copolymere aus Vinylhalogeniden und olefinen I. Qualitative IR‐spektroskopische untersuchungen an Vinylchlorid/Isobuten‐Copolymeren
Authors: Brück Dieter , Hummel Dieter O. 
Published: April 2003

AbstractDie IR‐Spektren einer Reihe strahlenchemisch bei 23°C hergestellter Vinylchlorid/Isobuten‐Copolymerer wurden im Bereich von 5000 bis 400 cm−1 untersucht. Der Vergleich mit den Spektren von Modellsubstanzen zeigte, daß die Monomerbausteine in den Copolymeren überwiegend in Kopf‐Schwanz‐Anordnung vorliegen. Die Zuordnung der Banden zu den verschiedenen Strukturen beruht auf ihrer Intensitätsänderung mit steigender Meßtemperatur und zunehmendem Isobutengehalt.
The catalytic effects of the poly(vinylpyridine)‐ligand in the oxidative polymerization of phenols
Authors: Tsuchida Eishun , Kaneko Masao , Nishide Hiroyuki 
Published: April 2003

AbstractIn order to study the catalytic effects of the polymer‐ligand, copper‐poly(vinylpyridine) (Cu‐PVP) complexes were used as catalyst for the oxidative polymerization of phenols. The catalysis was discussed.The rate of the 2,6‐dimethylphenol (XOH) polymerization catalyzed by the Cu‐PVP complex was slower than that catalyzed by a Cu‐pyridine complex. By the measurement of the kinetic constants, it was suggested that a bulky PVP ligand obstructed the coordination‐step of the monomer and the electron‐transfer‐step from the coordinated monomer to the cupric ion. The polymerization of the mixture of XOH and o‐cresol with Cu‐PVP as catalyst was saturated at a higher conversion, and the yield and the molecular weight of the polymer obtained were larger than in the cases where the Cu‐pyridine or the Cu‐γ‐picoline complex systems were used as catalysts. XOH is preferentially activated by the Cu‐PVP catalyst because its oxidation potential is lower, thus the effect of the PVP ligand may be observed.XOH was polymerized by the swelled Cu‐PVP complex as a heterogeneous catalyst in benzene or a benzene containing mixture of solvents. The catalyst was recovered by filtration in a high yield and re‐used repeatedly. Cu‐PVP complexes are relatively stable toward alkali because of their chelate structure. The polymerization was accelerated 3 to 5 times in alkaline solution, and the side‐reaction was suppressed.
Molecular size and configuration of poly(3‐vinylpyrene)
Authors: Sitaramaiah Gullapalli , Jacobs Darryl 
Published: April 2003

AbstractSolution properties of poly(3‐vinylpyrene) (PVπ) have been studied to determine the degree of hindrance to the flexibility of the vinyl chain by the pyrene pendant group. Fractionation of this polymer prepared by anionic polymerization, yielded nine narrow distribution fractions in the Mw range of 35 000–490 000 and the fractions were characterized by osmometry, light‐scattering and viscometry.Intrinsic viscosities of the fractions were obtained in chloroform and tetrahydrofuran at 25°C and in o‐dichlorobenzene at different temperatures from 25–80°C. From the KUHN‐MARK‐HOUWINK relationship, [η] = KMa, K and a values were determined and the exponent varied in the order, chloroform (a = 0.500) < tetrahydrofuran (a = 0.547) < o‐dichlorobenzene (a = 0.655) suggesting that chloroform at 25°C is a theta solvent for PVπ. Cloud point titration indicated that a mixture of THF/methanol in the ratio of 92:8 (V/V) is also a theta solvent for PVπ at 25°C. A KΘ value of 5.2·10−4 determined for PVπ at 25°C gave a value for the unperturbed dimension (R/M)1/2 of 5.77·10−9 cm. The conformational parameter, σ was computed as 2.84 for PVπ which suggests that the hindrance to rotation of the vinyl chain by the pyrene group is approximately the same as in the case of carbazole in poly(n‐vinylcarbazole). Values of [η] in o‐dichlorobenzene decreased with the increase of temperature yielding an average negative d log [η]/dT value of 1.1·10−3. The expansion factor decreased in all cases with the rise of temperature. A decrease of unperturbed dimension with the increase of temperature was reflected in the d log KΘ/dT value of −2.0·10−3 from which (R/M)1/2 at 80°C was computed as 5.35·10−9 cm.
Styrene/p‐methoxystyrene random copolymers. Part III. Some remarks on dilute solution properties
Authors: Pizzoli Maria , Ceccorulli Giuseppina , Stea Gianni 
Published: April 2003

AbstractStyrene/p‐methoxystyrene random copolymers of three different compositions and poly(p‐methoxystyrene) have been examined by viscosity measurements in some solvents (including good and Θ solvents) at different temperatures.Current theories have been applied to evaluate the FLORY constant KΘ; the values obtained for the copolymers are quite different from the “ideal” values and are independent on the temperature.The measurements in Θ solvents suggest that the conformations of the copolymers differ sometimes from the GAUSSian coil conformation.
Polymères optiquement actifs. XI. Polycondensats formophénoliques de la N‐benzoyl L‐tyrosine (TyB) et de la N‐p‐hydroxyphénylsulfonyl L‐phénylalanine (phhps). synthèse et activité optique
Authors: Beaumais Jacques , Vert Michel , Selegny Eric 
Published: April 2003

AbstractLes polymères du titre sont préparés par polycondensation en milieu acide (Pa) et en milieu alcalin (Pb) du formaldéhyde avec les monomères phénoliques optiquement actifs N‐benzoyl L‐tyrosine (TyB) et N‐(p‐hydroxyphénylsulfonyl)‐L‐phénylalanine (PhHPS). Leurs compositions chimiques sont vérifiées à partir des spectres IR, de la masse (Mr) du motif monomère et de la comparaison avec d'autres polycondensats du même type. PaTyB, PbTyB et PbPhHPS ont la structure chimique attendue, par contre, PaPhHPS fait l'objet d'une réaction secondaire qui est identifiée. Les pouvoirs rotatoires de PaTyB et PbTyB dépendent du milieu de polycondensation. L'ècart varie d'un solvant à l'autre. II ne s'annule que dans la potasse 0,l M en presence de fortes concentrations de sels (KCl, LiBr). L'influence de l'eau dans le dioxanne et des sels dans la potasse 0,l M est étudiée par dispersion rotatoire (DRO). Les contributions de DRO partielles negatives mises en évidence sont attribuées des espèces chimiques labiles entre les groupes amide portés par les motifs monomères et le co‐soluté (H2O, KCI, LiBr).
Vinyl polymerization by metal complexes. VI. On the initiation mechanism of vinyl polymerization by the α‐amino acid ester/copper(II) system
Authors: Azuma Koji , Inaki Yoshiaki , Takemoto Kiichi 
Published: April 2003

AbstractPolymerization of acrylonitrile and methyl methacrylate was studied in the presence of an α‐amino acid ester and copper(II) ion in dimethyl sulfoxide solution. The initiation mechanism of the polymerization by the α‐amino acid ester/copper(II) system was refered to the complex forming properties of the system, confirmed by spectroscopic measurements. The polymerization of both monomers was influenced by the kind of the α‐alkyl group of the α‐amino acid esters, but it was not affected by the kind of the ester groups. The carboxylic group of the esters was found to affect only the polymerization of methyl methacrylate. Based on the results, the character of the free radicals was discussed.
Cationic polymerizability of 1‐substituted vinyl ethers and styrenes
Authors: Masuda Toshio , Higashimura Toshinobu 
Published: April 2003

AbstractTo gain knowledge of the cationic polymerizability of 1,1‐disubstituted ethylenes, homopolymerizations of 1‐substituted vinyl ethers and styrenes, and also copolymerizations with the corresponding unsubstituted monomers are carried out. Methyl, ethyl, ethoxy, and phenyl groups are introduced in 1‐position. Ethyl 1‐methylvinyl ether and 1‐methylstyrene produce homopolymers in contrast to ethyl 1‐ethylvinyl ether, 1‐ethylstyrene and 1‐eth‐, oxystyrene which do not furnish the homopolymers. In the copolymerization, all of these 1,1‐disubstituted monomers are found to have greater reactivities for the unsubstituted propagating end than the corresponding unsubstituted monomers. It is concluded that 1,1‐disubstituted ethylenes suffer from steric hindrance in the cationic polymerization more than the corresponding 1,2‐disubstituted compounds, contrary to the situation in radical polymerizations. The change in reactivity of vinyl compounds with 1‐methyl substitution in various reactions is discussed.
Computer simulation of successively solutional refractionation of macromolecules
Authors: Kamide Kenji , Yamaguchi Keiko 
Published: April 2003

AbstractA successively solutional refractionation (SSRF) method, analogous to the successively precipitational refractionation (SPRF) method proposed by KAMIDE et al., has been simulated for a 1% solution of polymer having a SCHULZ‐ZIMM distribution (the ratio of the weight‐ to number‐average degree of polymerization, X̄w/X̄n = 2,0) with X̄w = 300. The combination of the number of the fractions, i, with the number of the sub‐fractions per each fraction, j, as expressed by (i˜j), were chosen so that ij was 15, such as (15˜1), (5˜3), and (3˜5). The fractionation efficiency decreases in the order: (15˜1), (5˜3), (3˜5), (0˜15), where (0˜15) denotes the simple successive solutional fractionation which yields 15 fractions as a total number of the fractions. The (3˜5) and (5˜3) type refractionations were found to be very effective, except for a few initial fractions, to obtain fractions with X̄w/X̄n≤1,1. The two methods, i.e., the SCHULZ method and KAMIDE et al. method, for evaluating the cumulative molecular size distribution of the original polymer were compared with each other by using the refractionation data (X̄w and the amount of the subfractions). The SCHULZ method is apparently advantageous over the KAMIDE et al. method. SSRF is concluded to be suitable not for analytical purposes, but for preparative purposes.
Pyrolysis gas chromatographic investigation of ionically chlorinated polystyrenes
Authors: Okumoto Tadaoki , Takeuchi Tsugio 
Published: April 2003

AbstractThe microstructure of ionically chlorinated polystyrene with or without a catalyst and the distribution of chlorine in the aromatic nucleus of the polymers were studied by means of pyrolysis gas chromatography. Chlorinated polystyrene was pyrolyzed to yield characteristic chlorostyrenes (ortho and para) and dichlorostyrenes (2,4‐, 2,5‐, and 3,4‐) which gave good informations about substitution of the aromatic nucleus in the original polystyrene. The differences between two series of ionically chlorinated polystyrenes were also discussed from the yields of styrenes and monochlorostyrenes.