摘要:

AbstractInsbesondere um den Einfluß der Wechselwirkung zwischen Nachbargruppen auf das Verhalten wäßriger Polyelektrolytlösungen zu verstehen, wurden potentiometrische Messungen an Polyelektrolyten mit verschiedener Stereostruktur und verschiedener Verteilung der ionisierenden Gruppen auf der Polymerkette, auch an copolymerisierten Elektrolyten mit nichtionisierbaren Comonomeren, durchgeführt. Auf Grund solcher Untersuchungen wurde die Herstellung von Polyelektrolyten mit etwas veränderter Taktizität durch radikalische Polymerisation bei höherer Temperatur versucht. Der Einfluß einiger Seitenzweige der Makromoleküle auf das Verhalten der Polyelektrolytlösungen und die Quellung von vernetzten Polyelektrolyten wurden ebenfalls untersucht. Aus den Ergebnissen ist zu schließen, daß das Verhalten der Polyelektrolytlösungen von der Wechselwirkung zwischen Nachbargruppen und von der Hyperknäuelung stark beEinflußt werden kann. Unsere Experimente zeigen außerdem, daß die Bedingungen der Radikalpolymerisation die Stereoregularität der Polymerisate erheblich b

ISSN:0025-116X    

DOI:10.1002/macp.1963.020610101

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

摘要:

AbstractDynamic mechanical properties (sound velocity and damping factor Q−1) have been determined in some amorphous ethylene‐propylene copolymers from −170 to −15°C. by an electrostatic method at a frequency of the order of 104Hz.Two abrupt changes of slope are observed in the v—T curves, one at T'g(−120°C.) and one at Tg(−30 to −55°C.) and two regions of high dissipation are noticed in the Q−1‐T curves, one at temperatures between T'gand Tgand one at temperatures above Tg.The transition at T'gand the lower temperature relaxation phenomenon are both attributed to molecular motions of CH2 groups in the main chain and of a limited number of chain elements containing CH3branching. The transition at Tgand the higher temperature relaxation phenomenon are connected with motions of large sections of the chain.The experimental results are discussed on the basis of the structure of ethylene‐propylene copolymers and suggestions are made concerning the use of dynamic mechanical data for the charact

ISSN:0025-116X    

DOI:10.1002/macp.1963.020610102

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

摘要:

AbstractDans le présent article est proposé un mécanisme de la polymérisation stéréospécifique de l'isoprène par le lithium métallique. Cette polymérisation se fait par l'intermédiaire de composés organolithiens solubles dont le caractère difonctionnel a pu être mis en évidence par des essais de copolymérisation séquencée. L'étude des vitesses de polymérisation et des masses moléculaires des polymères obtenus a montré que, lorsque les extrêmités organo métalliques de ces composés ne sont pas engagées dans des complexes d'association, elles sont responsables de la polymérisation simplement par additions successi

ISSN:0025-116X    

DOI:10.1002/macp.1963.020610103

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

摘要:

AbstractThe main results of a kinetic investigation on the formation of amorphous and crystalline polyethylidene from the decomposition of diazoethane catalyzed by colloidal gold are reported.The data on the dependence of the degree of polymerization of amorphous polyethylidene from the initial concentration of diazoethane suggest chain transfer reactions with undecomposed diazoethane as a probable mechanism of termination of the polyethylidene chains this would be confirmed by the number of the terminal unsaturation in the polymer chain, which has been found to be close to two. The results are in accordance to the previously formulated working hypotheses on the mechanism of the formation of polyalkylidenes from the metal catalyzed decomposition of diazoalkanes.

ISSN:0025-116X    

DOI:10.1002/macp.1963.020610104

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

摘要:

AbstractThe results obtained from a systematic kinetic study of ethylene‐propylene copolymerization in the presence of catalysts prepared from Al(C6H13)3and VCl4, already reported are briefly summarized.The considerable increase of the overall copolymerization rate, observed with the increase of the ratio of ethylene to propylene in the reacting liquid phase, cannot be explained only on the basis of the values of the kinetic constants of propagation, but it is also necessary to admit a variation in the concentration of the number of growing chains. Some experimental evidences are indicated proving this hypothesis.This result cannot be extended to the ethylene‐propylene copolymerization in the presence of other catalytic systems acting through an anionic co‐ordinated mechanism, for which the ratio between the rates of ethylene and propylene homopolymerization is very close to the value of the reactivity ratio of ethylene.Finally, an equation is proposed which interprets, to a good approximation, the values of the overall rate of the copolymerization process in the presence of the catalytic system Al(C6H13)3

ISSN:0025-116X    

DOI:10.1002/macp.1963.020610105

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

摘要:

AbstractTwo hypothesis are proposed on the formation of vinyl double bonds in polypropylenes obtained in anionic coordination polymerization at temperatures above 100°C.According to the first hypothesis, the vinyl double bonds originate from a termination mechanism during which one of the hydrogen atoms in the methyl group of propylene combines with the growing macromolecule, while the remaining allyl group combines with the catalytic complex. The metal‐allyl bond could thus bring about a new macromolecule containing a vinyl double bond as terminal group. Some experimental evidence supporting this hypothesis are examined.Afterwards, an other hypothesis, based on the results obtained by K. ZIEGLER and coworker on pyrolyzing some isoalkylaluminum compounds has been discuss

ISSN:0025-116X    

DOI:10.1002/macp.1963.020610106

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

摘要:

AbstractThe X‐Ray crystal structure refinement of (AlCl2CH3)2is described in this paper; itsknowledge may be of interest because it is well known that the organometallic alluminium compounds may be used for the preparation of catalytic systems in certain stereospecific polymerizations.The space group has resulted to be C2/c; the dimeric molecules, with chlorine bridges, are placed on crystallographic symmetry centres, thus giving rise to a “trans” molecular configuration. The tetrahedral coordination around aluminum atoms results to be distorted so that, in particular, the value of the angle (bridged chlorine atoms) approaches 90°. Al—Cl distances to bridged chlorine atoms result, as it was expected, to be longer (2.25 ± 0.01 Å) than the corresponding distances to non‐bridged atoms (2.

ISSN:0025-116X    

DOI:10.1002/macp.1963.020610107

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

摘要:

AbstractThe conditions for obtaining polybenzofuran with high optical activity using the system AlCl3/β‐phenylalanine as catalyst are described. The behaviour of the asymmetric synthesis is examined during the course of the reaction, and the relationship between the rotatory power and the degree of polymerization of the polymer is discussed.A polymerization mechanism is proposed, which comprises a process of asymmetric growth (in which a counterion containign phenylalanine conditions the configuration of each monomeric unit) and a racemizing termination process. This hypothesis explains the experimental facts, particularly the constancy of [α] with varying [η]and the progressive deterioration of the asymmetric synthesis during the polymeriza

ISSN:0025-116X    

DOI:10.1002/macp.1963.020610108

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

摘要:

AbstractThe paper describes preparation and properties of butadiene‐pentadiene copolymers obtained with homogeneous systems prepared from Al(C2H5)Cl alcl and vanadium trichloride tetrahydrofuranate or vanadium triacetylacetonate, respectively. A brief examination of the catalyst forming reaction is included. Copolymers of every composition can be obtained. The influence of time and temperature of aging of the catalyst on copolymer yield is reported. The copolymers are richer in pentadiene than the corresponding monomer mixtures. Irrespective of the copolymer composition the butadiene units are alltrans‐1,4 and the pentadiene units are partlytrans‐1,4 and partly 1,2. The transition (Tt) and melting temperatures (Tm) of the copolymers decrease with increasing C5content. Copolymers constituted of about 23 mole‐% C5have Tmnear 20°C. The latter copolymers give, after vulcanization, good elastomers, which are able to crystallize under stretching. At room temperature, the now appearing crystallinity is characteristic of the modification oftrans‐1,4 polybutadiene which is stable

ISSN:0025-116X    

DOI:10.1002/macp.1963.020610109

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

摘要:

AbstractThe autocatalytic peroxidation performed dircectly with air of linear polybutene in the absence of special initiators was studied; hydroperoxides, peroxides, “active” hydrogen, alcohols were determined by chemical methods in the oxidized product, and the ketonic carbonyls were determined qualitatively by I.R. analysis.The variation with oxidation time of the quoted chemical functions was also determined.It results that the polymer degrades in a direct ratio with the content of active oxygen, that, at the beginning of the reaction, the amount of peroxides is negligible but the ratio between these and the hydroperoxides increases with time and after about 2 hrs. alcohols, hydroperoxides and peroxides are present in the oxidized product in comparable amounts, whereas acids appear only after about 8 hrs. of react

ISSN:0025-116X    

DOI:10.1002/macp.1963.020610110

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY