bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modification des polyméres de vinyl‐4 benzophénones méthoxylées et copolymérisation des monomères avec le styréne
Authors: Pinazzi Chr. P. , Fernandez A. 
Published: April 2003

AbstractLes monomères cités ont été copolymérisés radicalairement dans le benzene avec le styrène. La composition des copolymères a été déterminée à partir de leurs spectres NMR. Les constantes r1 et r2 été détérminée d calculdes; dans ce cas, les p‐vinylbenzopédnones méthoxy‐lées ont une plus grande réactivité que le styrene. Les homo et copolymkres de ces p‐vinyl‐benzophdnones n'ont aucun effet protecteur contre le rayonnement UV. La condition nécessaire pour obtenir cet effet est la pédsence d'un groupement hydroxyle en position ortho par rapport au groupement carbonyle. La déméthylation partielle des polyméres des vinyl‐4 méthoxy‐2′ benzophénones a été étudiée dans ce but. Cette réaction a permis d'obtenir en particulier la poly(viny1‐4 hydroxy‐2′ mdthoxy‐4′ benzophenone) dont le spectre UV indique un effet protecteur contre la lurnière naturelle.
Self polycondensation of oxalyl dihydrazide
Authors: Lehtinen Arja , Sundquist Jorma 
Published: April 2003

AbstractIn order to obtain a linear poly(1,3,4‐oxadiazole‐2,5‐diyl) the self‐polycondensation of oxalyl dihydrazide has been investigated. Polymers with molecular weight up to 6000 were prepared by solution polycondensation in N‐methylpyrrolidone containing lithiumchloride. These polymers are thermally stable up to 300°C. They were characterized by IR spectra, thermal analysis and solubilities.
Aqueous polymerization of methacrylamide initiated by acidified bromate/thiourea redox system
Authors: Misra G. S. , Gupta C. V. 
Published: April 2003

AbstractThe polymerization of methacrylamide initiated by acidified bromate/thiourea has been studied at 35 ± 0,2°C in a nitrogen atmosphere. The rǒle of the acid (HCl) is to convert thiourea to isothiourea with a faster rate in contrast to a neutral or alkaline medium, and thus producing free radicals by oxidation of the latter. The rate of polymerization is independent of the activator (thiourea) concentration within the range of 0,4–1,0 · 10−2 mol/dm3 or very low (0,4 · 10−2 mol/dm3) concentrations of the activator. The rate varies linearly at low monomer concentration (up to 17,64 · 10−2 mol/dm3). The catalyst exponent comes out to be unit (1,1) in the studied range of the catalyst (KBrO3) concentration. This might be due to the collision of an active centre with a chain breaking agent. The addition of a strong acid (HCl) within the pH range of 1,75–1,9 results in no change of the initial rate; the maximum conversion decreases, however, with the activator alone, an optimum being observed at pH 1,9. The initial rate and the limiting conversion increase with the increase in polymerization temperature up to 35 ± 0,2°C. The overall activation energy has been found to be 18,9 Kcal/mol within the temperature range of 25–45°C.Organic solvents (only water miscible) and small amounts of neutral salts (KCl and Na2SO4) depress the initial rate and the maximum conversion. The addition of Na2F2 does not show any variation in the polymerization rate in contrast to Cu‐ and Fe‐Salts.
Mathematical model of polyaddition of 1‐chloro‐2,3‐epoxypropane to α, ω‐diols
Authors: Novák Jiří , Šváb Vladimír 
Published: April 2003

AbstractA mathematical model for the composition of products resulting from a polyaddition of 1‐chloro‐2,3‐epoxypropane to ethylene glycol was constructed on the presumption that the reactivites of the 3‐chloro‐2‐hydroxypropyloxy end groups are equal, that the remaining hydroxyl groups have also identical reactivities, and that the oxirane ring opens to give exclusively Cα‐ethers. By comparing the calculated and experimentally obtained percentage of unreacted ethylene glycol (for various chosen kinetic parameters) at variable initial mole ratios in the moment of complete conversion of 1‐chloro‐2,3‐epoxypropane, the relative reactivities of all three hydroxyl groups could be determined. The reactivity ratio of the hydroxyl group in the 3‐chloro‐2‐hydroxypropyloxy end group to the initial hydroxyl group in the diol was found to be 0,6 and that of the remaining diol group to the initial diol group to be 0,5.
Crystallization of polypeptides in the course of polymerization, 2. Chain folded crystals of polyglycine and poly‐β‐alanine
Authors: Komoto Tadashi , Kim Kea Yong , Minoshima Yoshiaki , Oya Masanao , Kawai Toru 
Published: April 2003

AbstractThe polymerization of N‐carboxy anhydrides of glycine and β‐alanine was studied in acetonitrile with butylamine as initiator. As was expected from the similarity of the backbone chain structure to nylons, the polymer precipitated in the form of a spherulite consisting of ribbon like crystalline units just as in the case of nylons previously reported. The molecules in the ribbon like crystals were arranged antiparallel forming a hydrogenbonded sheet. The result contrasts with that reported previously on some α‐amino acids which gave helical polymer molecules organized in the form of an extended chain crystal. The mechanism of the crystal growth has been discussed along the same line as in the case of nylons.
Funktionelle monomere und polymere. X. Wechselwirkung zwischen nucleinbasenhaltigen makromolekülen
Authors: Kawakubo Fumio , Kondo Koichi , Takemoto Kiichi 
Published: April 2003

AbstractEinige monomere, dimere und polymere Derivate von N‐Methylaminopurin, N,N‐Dimethylaminopurin und Äthoxypyrimidon wurden dargestellt. Die NMR‐ und UV‐Spektren dieser neuen Substanzen wurden gemessen und miteinander verglichen. Außerdem wurden die Polymer‐Polymer‐Wechselwirkungen spektroskopisch untersucht. Es ergab sich, daß nur Poly(9‐vinyladenin) und Poly[6(N‐methylamino)‐9‐vinylpurin] mit Ribonucleinsäure in wäßriger Lösung hypochrome Effekte zeigen.
Ein neuer weg zur synthese von polystyrol und styrol‐copolymeren mit primären aromatischen aminogruppen
Authors: Seliger Hartmut 
Published: April 2003

AbstractEs wird ein Verfahren zur Überführung aromatischer Nitrogruppen von Polymeren des Styrols in primäre aromatische Aminogruppen beschrieben, bei dem Phenylhydrazin als Reduktionsmittel angewandt wird. Polystyrole von verschiedenem Nitrierungsgrad sowie Copolymere von Styrol mit Divinylbenzol, Methylacrylat und 4‐Vinylpyridin wurden untersucht. Die Reaktion verläuft in Lösung von Phenylhydrazin allein oder in Mischungen geeigneter Lösungsmittel bei höherer Temperatur quantitativ und ohne Vernetzung löslicher Polymerer.
Polymerization of aromatic aldehydes, 8. Cationic copolymerization of 2,2′‐biphenyldicarbaldehyde with styrene
Authors: Kunitake Toyoki , Tsugawa Shunichi , Aso Chuji 
Published: April 2003

AbstractCationic copolymerizations of 2,2′‐biphenyldicarbaldehyde (II) (diphenaldehyde) with styrene were carried out with BF3O(C2H5)2 in dichloromethane. The copolymers were white powders (MW: 6000∼7000) and soluble in common organic solvents. The monomer reactivity ratios (BF3O(C2H5)2, CH2Cl2, −78°C) were: r1 (II) = 0,13 ± 0,07; r2 (styrene) = 0,70 ± 0,05. The IR data showed the presence of pendant aldehyde groups corresponding to 20–40% of II units. The content of pendant aldehyde groups increased with the content of II in the copolymer. Therefore, the intramolecular cyclization of II must occur in competition with the monomer addition during the propagation step. Recovery of the bis‐hydrazone of II on acid hydrolysis of the copolymer was consistent with the monomer sequence estimated from the reactivity ratio. Attempted homopolymerization of II was not successful.
Die copolymerisation von trans, trans, cis‐1,5,9‐cyclododecatrien mit methylacrylat
Authors: Tokarzewski Ludomir , Socha Jerzy 
Published: April 2003

AbstractDie Copolymerisation des Systems Methylacrylat/Cyclododecatrien wurde untersucht. Die Copolymerisationsparameter wurden bestimmt und die Eigenschaften der Copolymeren untersucht.
Determination of the basicity of some cyclic ethers and cyclic formals
Authors: Mateva R. , Fratev F. , Pavlova M. 
Published: April 2003

AbstractThe tendency of some cyclic ethers and cyclic formals (“oxacyclic compounds”) to form protonated complexes was studied by means of UV spectroscopy. The degree of basicity (pKBH+) was evaluated on the basis of the HAMMET indicator functions.The process of complex formation was followed at different values of the HAMMET function in dilute spectroscopically pure sulfuric acid. The pKBH+ values of four of the seven examined compounds correlated very well with the pKBH+ values obtained by a method different in principle. This was taken as an indication of the objectivity of the evaluation of the basicity of the “oxacyclic compounds” by spectral methods regardless of the fact that these compounds are very weak bases and form colourless protonated complexes.
Crystallization of polypeptides in the course of polymerization, III. Further studies on the growth mechanisms of poly(L‐alanine) crystals
Authors: Fujie Akira , Kōmoto Tadashi , Ōya Masanao , Kawai Tōru 
Published: April 2003

AbstractIn order to establish the mechanism proposed previously for the formation of the extended chain crystals during the heterogeneous polymerization of the LEUCHS anhydride 4‐methyl‐2,5‐oxazolidinedione (L‐alanine NCA) in acetonitrile, oligo‐L‐alanines were prepared by purely organic chemical methods. Their solubility, conformations in various solvents and those in the crystallized states were studied and compared with those in the crystals formed directly in the course of the heterogeneous polymerization. It was found that the growing chain molecules became insoluble in acetonitrile and crystallized into the β‐conformation when they attained a \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {\rm{DP}} $\end{document}
of 3.As the growing chains in the course of the heterogeneous polymerization attained \documentclass{article}\pagestyle{empty}\begin{document}$\overline {\rm{DP}}$\end{document} of 10–13 (i.e. 7–10 from the basal plane of the original skeleton crystals) by further polymerization, they crystallized into the α‐helical conformation. Due to the topochemical nature of the chain growth, this critical length for the formation of the α‐helix is shorter than that found in solution for the corresponding oligomers already synthesized (i.e., \documentclass{article}\pagestyle{empty}\begin{document}$\overline {\rm{DP}}$\end{document} > 10).It was also shown that the crystalline nuclei with the β‐conformation, formed in the very early stages of the polymerization, remain throughout the polymerization.In order to examine the rôle of acetonitrile in this particular type of polymerization, the polymerization of L‐alanine NCA was studied also in dioxane and propionitrile. The chains grown from the basal plane of the skeleton crystals with the β‐conformation remain in some state like random coils until they attain the critical length for the formation of the α‐helix. This critical length seems to depend on the solvation power (including the steric factor) of the solvent used. In the case of acetonitrile, the dipole‐dipole interaction with polypeptides may play an important rǒle in this type of solvation.
Synthese und reaktionen difunktioneller N‐acyl‐β‐lactame
Authors: Kricheldorf Hans R. 
Published: April 2003

AbstractDie Darstellung difunktioneller N‐Acyl‐β‐lactame gelingt am besten durch Acylierung von N‐Trimethylsilyl‐lactamen mit geeigneten Säurechloriden unter Abspaltung von Trimethylchlorsilan. N‐Acyl‐β‐lactame reagieren leicht mit Aminen und Alkoholen, wobei ausschließlich Ringöffnung erfolgt. Durch Additionspolymerisation difunktioneller N‐Acyl‐β‐lactame an Diamine, Diole oder Amidoalkohole ist eine Vielzahl von Polymeren verschiedener Struktur zugänglich, die neben Amidgruppen auch Harnstoff‐, Thioharnstoff‐, Urethan‐ oder Estergruppen in regelmäßigen oder unregelmäßigen Sequenzen enthalten.
Polymères liquides à extrémités alkoxysilanes
Authors: Brossas Jean , Pinazzi Christian P. , Clouet Gilbert , Clouet Françoise 
Published: April 2003

AbstractNous avons effectué la synthèse de polymères à bas masses moléculaires rélatives — polymères liquides — susceptibles d'une part d'être compatibles avec des résines polyester et d'autre part de pouvoir effectuer des liaisons chimiques avec les structures silanols libres du verre. Pour cela, nous avons préparé des polydiènes α,ω‐dicarbanioniques isomoléculaires et nous avons ensuite effectué la réaction de terminaison par addition d' alkoxychlorosilanes. Afin d'étudier les structures obtenues, nous avons préparé des substances modèles, notamment à partir de terpénoïdes naturels.
On the mechanism of anionic polymerization of maleic anhydride, 2
Authors: Zweifel Hans , Völker Theodor 
Published: April 2003

AbstractThe triphenyl and tributyl phosphine initiated polymerization of maleic anhydride was investigated. The structure of the macro zwitterions, formed under the given reaction conditions, depended on the initiator employed. If the polymerization was initiated by triphenyl phosphine, the macromolecules contained succinic anhydride units and cyclopentanone derivatives, formed from further rearrangement. If, however, tributyl phosphine was employed as initiator, the polymers were mostly made up of conjugated ketoolefinic units. IR, NMR and mass spectrometric measurements were carried out to determine the structure of the polymers. Existence of the macro zwitterions was proved by high voltage electrophoresis.The semi‐conductor properties of the polymers containing conjugated ketoolefinic units are discussed.Spectroscopic investigation of the kinetics of the triphenyl phosphine initiated polymerization of maleic anhydride showed that the initiation reaction of the ylide, formed with the monomer, proceeded about 90 times slower than the propagation reaction due to addition of the monomer to the growing chain‐end.
Influence du degré de ramification sur la température «theta» de quelques polymères dans différents solvants
Authors: Candau Françoise , Strazielle Claude , Benoit Henri 
Published: April 2003

AbstractL'abaissement de la temperature Θ observé pour les polystyrènes ramifiés dans le cyclohexane est généralisé a d'autres systèmes: polystyrène dans 1e malonate d'éthyle, la décaline et un mélange de solvants (benzène 78%, méthanol 22%) — ainsi qu'à d'autres polymères tels que le polyisoprène dans la méthylpropylcétone et l'acétate de polyvinyle en solution dans la heptanone‐3 et l'éthanol.La température Θ (mesurée par diffusion de la lumière) et la température de précipitation Tp (mesurée par méthode de séparation de phase) de ces polymères est inférieure dans tous les cas à celle des polymbres linéaires de même nature chimique. L'abaissement ΔΘ observé croit avec le degré de ramification.
Studies on organometallic compounds as polymerization catalysts, 6. Diethylcadmium/additive system for propylene oxide polymerization
Authors: Ishimori Michihiro , Nakasugi Osami , Yokobori Katsuichi , Tsuruta Teiji 
Published: April 2003

AbstractOrganocadmium compounds as catalysts for propylene oxide polymerization were studied. It was found that the Cd(C2H5)2CH3COSH system has an excellent catalytic activity for reactions forming polymers of high rel. mol. mass. In contrast, Cd(C2H5)2ROH, RSH and RCOOH systems showed little or no catalytic activity. The favoured activity of the Cd(C2H5)2CH3COSH system is discussed in terms of dπ  dπ bonding, on the basis of spectroscopic studies.
Kinetics of chain growth in binary copolymerization
Authors: Tosi Camillo , Chioccola Giampiero 
Published: April 2003

AbstractThe chain propagation step in binary copolymerizations was studied. The composition of copolymers with any arbitrary degree of polymerization was compared with the stationary limit, obtained from the differential form of the copolymerization equation and determined by the transition probabilities alone. It was shown that the n‐mer composition approaches the value characteristic of the copolymer in a manner which differs not only quantitatively but also qualitatively, depending on the product of the reactivity ratios. The three cases of physical significance, viz. block (r1r2 > 1), random (r1r2 = 1) and alternating (r1r2 < 1) copolymers, are thoroughly discussed.
Cellulose single crystals
Authors: Ramesh Ravi , Patel Chiman K. , Patel Raman D. 
Published: April 2003

AbstractAn attempt was made to crystallize cellulose II by hydrolyzing cellulose acetate (DP = 345) in dilute acetic acid medium. Though the cellulose chains are known to be less flexible, they exhibit a crystal structure similar to that obtained for flexible synthetic polymers. The effects of temperature and of acetic acid concentration on the crystal structure were studied. It was shown that cellulose could be crystallized in a variety of structural features if the strong intermolecular hydrogen bonding, which under ordinary circumstances dominates the flexibility of the backbone, is avoided by appropriate experimental conditions.
Contribution à l'étude des propriétés électriques et mécaniques dynamiques de quelques polyéthylènes chlorés à saturation
Authors: Nguyen Ung Long , Berticat Philippe , May Jean‐François , Vallet Georges 
Published: April 2003

AbstractLes propriétés électriques de polyéthylènes chlorés en suspension (taux de chlore, 73% environ) ont été étudiées à la fréquence de 5 MHz dans une gamme de température de 20 à 80°C. Les relaxations observées varient avec la structure chimique du polymère.Les propriétés mécaniques dynamiques ont été étudiées en basse fréquence dans une gamme de température de −100 à +190°C. On n'observe pas de parallélisme entre propriétés électriques et mécaniques pour ces polymères dont les chaînes sont très rigides.
Über die synthese und die eigenschaften einiger mono‐, bis‐ und poly‐azine aromatischer heterocyclen
Authors: Manecke Georg , Kautz Johannes 
Published: April 2003

AbstractPolymere (Polyazine), die das reversible, bivalente Redoxsystem der 2,2′‐Azine aromatischer Heterocyclen enthalten, wurden aus bifunktionellen Salzen und Hydrazin dargestellt. Aus diesen Salzen und Hydrazonen wurden Bisazine als Modellverbindungen für die Polyazine erhalten. Durch Oxidation wurden Poly‐ und Bi‐Radikale dargestellt, die durch ihre ESR‐Spektren und die elektrische Leitfähigkeit charakterisiert wurden. Die Bisazine wurden polarographisch untersucht.
Influence de la masse moléculaire, de la polydispersité et de la température sur les phénomènes de solvatation préférentielle de polystyrènes linéaires dans différents mélanges de solvant
Authors: Hert Marius , Strazielle Claude , Benoit Henri 
Published: April 2003

AbstractDans cet article nous présentons les résultats d'une étude de l'adsorption préférentielle du polystyrène en mélange de solvants en fonction de différents paramètres. En premier lieu, nous avons examiné l'influence de la densité en segments intramoléculaire (effet de la masse moléculaire et de la polydispersité du polymère) sur ce phénomène. L'effet de la température sur le coefficient de solvatation a également été considéré. Pour certains de nos résultats expérimentaux, il existe un bon accord avec les théories thermodynamiques de l'adsorption préférentielle, cependant le manque de connaissances relatives à la variation avec la densité en segments intramoléculaires et la température, des paramètres d'interaction thermodynamiques, ne permet pas une étude quantitative rigoureuse.
Über synthese und polymerisation von ß‐aminosäure‐N‐carbonsäureanhydriden
Authors: Kricheldorf Hans R. 
Published: April 2003

AbstractDurch Hydrolyse von ß‐Isocyanatocarbonsäure‐trimethylsilylestern, die aus cyclischen Carbonsäureanhydriden mittels Trimethylsilylazid (8) gewonnen wurden, konnten neue ß‐Aminosäure‐N‐carbonsäureanhydride dargestellt werden. Aus der Untersuchung der Polymerisation von 9 ß‐Aminosäure‐N‐carbonsäureanhydriden mit verschiedenen basischen Katalysatoren und unter verschiedenen Reaktionsbedingungen ging hervor, daß die Wirksamkeit der Katalysatoren mit zunehmender Basizität steigt und die höchsten rel. mol. Massen mit den am wenigsten basischen Katalysatoren oder auch bei niederen Reaktionstemperaturen erhalten werden. Die aufgrund von elementaranalytischen und NMR‐spektroskopischen Endgruppenbestimmungen errechneten rel. mol. Massen liegen in keinem Falle über 10000. Bei der thermischen Decarboxylierung der N‐Carbonsäureanhydride entstanden neben den Polyamiden auch niedermolekulare Nebenprodukte. ß‐Lactame konnten nicht nachgewiesen werden.
Effect of average molecular weight of the original polymer on phase separation characteristics of multicomponent polymer/single solvent system
Authors: Kamide Kenji , Miyazaki Yukio , Sugamiya Ken 
Published: April 2003

AbstractWhen solutions of a polymer with a molecular weight distribution (MWD) having a great variety of the average molecular weights are precipitationally fractionated, the effect of the average molecular weight on the phase separation features can be discussed by means of a hypothetical calculation technique.The FLORY‐HUGGINS‐FUJISHIRO theory was employed as a basic tenet for the simulation. The partition coefficient, σ, as well as the volume ratio of the polymer‐lean phase to the polymer‐rich phase, R, decrease with an increase in the average molecular weight of the original polymer under the same operating conditions, including initial concentration, vpo, the concentration dependence of the polymer/solvent interaction parameter, p, and the amount of fraction, p. The standard deviation of the fraction, σ', (Eq. (3)), for a given p reveals a maximum at a specific vpo. In the cases where the original polymers differ in the average molecular weight, but have the same X̄w/X̄n and where the original polymers have the same σ', the fractionation efficiency, defined by \documentclass{article}\pagestyle{empty}\begin{document}$ (\overline X _w /\overline X _n )/(\overline X _w^0 /\overline X _n^0 ) $\end{document}, is lowered with a decrease in the average molecular weight (suffix zero means the original polymer), i.e., the molecular weight distribution of the fractions, obtained under the same operating conditions, becomes broader. The average molecular weight of the original polymer affects insignificantly the characteristics, but the accuracy of estimating the MWD of the original polymer becomes inferior.
Effect of molecular weight distribution of the original polymer on separation characteristics in successive precipitational fractionation
Authors: Kamide Kenji , Yamaguchi Keiko , Miyazaki Yukio 
Published: April 2003

AbstractAn attempt has been made to confirm the validity of conclusions deduced in the previous papers in which a single sample with a specific molecular weight distribution, was mathematically fractionated. Polymers with a SCHULZ‐ZIMM distribution and WESSLAU distribution (ratio of the weight‐ to number‐average degree of polymerization, X̄w/X̄n = 1,05–5) were brought into a solution, which was cooled to cause precipitation according to the simulative procedure of KAMIDE and SUGAMIYA. The molecular weight distribution (MWD) of the fractions is approximately symmetrical and can be expressed by the normal distribution function, irrespective of the MWD of the original polymer. If the MWD of the original polymer is highly skew in the lower molecular weight region, the fraction, separated from a comparatively concentrated solution at very small p, yields a doubly‐peaked MWD (p is the amount of fraction expressed as weight ratio). As the width of the MWD of the original polymer increases, the MWD of the higher order fraction becomes narrower and X̄w of the fraction decreases rapidly in the fractionation process. The standard deviation, σ' for the polymer in the polymer‐rich phase is larger than that in the polymer‐lean phase, regardless of the type and breadth of the MWD of the original polymer, and the order of fractionation, provided that the fraction size is small. When the initial concentration is not exceedingly low, the KAMIDE method is by far preferable to the SCHULZ method for estimating accurately the MWD of the original polymer from the fractionation data. In a given fractionation run the log‐log plot of polymer concentration in a precipitate vs. X̄w can be approximated by a straight line.