摘要:

AbstractEs wurden die unlöslichen Koordinationsverbindungen von Ru, Rh und Pd mit den amorphen Polymeren des 2‐, 3‐ und 4‐Vinylpyridins sowie mit demisotaktischenund demsyndiotaktischenPolymeren des 2‐Vinylpyridins dargestellt. Das Molverhältnis zwischen dem Metallchlorid und der Monomereinheit des Vinylpyridins in den Ausgangsgemischen wurde mit dem in den resultierenden Koordinationsverbindungen verglichen und die chemische Zusammensetzung der letzteren bestimmt. Anhand der gefundenen Daten wird der wahrscheinliche Charakter der isolierten Koordinationsverbindungen der Poly(vinylpyridin)e d

ISSN:0025-116X    

DOI:10.1002/macp.1976.021770101

出版商:Hüthig&Wepf Verlag    

年代:1976

数据来源: WILEY

摘要:

AbstractCarbon dioxide and propylene oxide (PO) were copolymerized using diethylzinc in addition with benzenedi‐ and triols, aliphatic diols and triols, and aminophenols as catalyst systems. A large amount of CO2/PO alternating copolymer, {poly(propylene carbonate), poly(oxycarbonyloxypropylene), of high molecular weight was obtained using the homogeneous (C2H5)2Zn/pyrogallol (2:1 by mole) system (1). The (C2H5)2Zn/o‐aminophenol system (2) (also homogeneous) appeared to be much less active in the copolymerization of CO2with PO than the former one. From the other studied systems, that appeared to be heterogeneous, (C2H5)2Zn/resorcinol (1:1 by mole) was the most active one, but less active than the system1.Further, the copolymerization of CO2and PO was studied in the presence of the (C2H5)2Zn/resorcinol (1:1 by mole) system at various temperatures and in reaction media of different basicity.On the basis of the obtained results of the copolymerization of CO2with PO and of measurements of the quantity of ethane evolved in the reactions between the catalytic systems' components, structures of several catalysts, particularly homogeneous ones, are suggested and some aspects of the copolymerization mechanism are discus

ISSN:0025-116X    

DOI:10.1002/macp.1976.021770102

出版商:Hüthig&Wepf Verlag    

年代:1976

数据来源: WILEY

摘要:

AbstractThe homogeneous redox polymerization of acrylamide by the citric acid/permanganate initiating system was investigated at 35±0,2°C under nitrogen. Variation of the activator concentration in the range of 2,5.10−3to 20,0.10−3mol/dm3had no effect on the rate of polymerization. The initial rate increased with the increasing catalyst concentration and a value of nearly unity of the catalyst exponent confirmed a unimolecular chain termination process. The rate varied linearly with the monomer concentration over a wide range (5,0.10−2to 20,0.10−2mol/dm3). The initial rate increased with the increasing temperature but the maximum conversion showed a decrease as the temperature was raised above 35°C. The energy of activation, in the temperature range of 25 to 45°C, was found to be 55,90kJ/mol (13,36 kcal/mol).The addition of neutral salts, Co(NO3)2, Ni(NO3)2, organic solvents, and complexing agents, all water soluble, reduced the rate and percentage of conversion. The introduction of MnSO4or of more catalyst (at intermediate stages) into the system increased both the rate and limiting

ISSN:0025-116X    

DOI:10.1002/macp.1976.021770103

出版商:Hüthig&Wepf Verlag    

年代:1976

数据来源: WILEY

摘要:

AbstractDie Olefin‐Metathese von mehrfach ungesättigten Carbonsäureestern wie Linol‐ und Linolensäureester in Gegenwart eines WCl6/(CH3)4Sn‐Katalysators führt neben einem cyclischen Produkt zu linearen oligomeren Olefinen, Mono‐ und Diestern. Die Produkte werden durch Massenspektrometrie identifiziert. Die sich im Gleichgewicht einstellende Verteilung der Linearprodukte wird statistisch berechnet und mit der experimentellen Verteilung

ISSN:0025-116X    

DOI:10.1002/macp.1976.021770104

出版商:Hüthig&Wepf Verlag    

年代:1976

数据来源: WILEY

摘要:

AbstractRandom copolymers of styrene and methacrylic acid were prepared in a wide composition range, and their conformational properties were investigated by potentiometric methods in different solvent media. A conformational transition occurs as a function of the degree of ionization (α). The Gibbs free energy change of the transition between uncharged conformers (ΔG0) was determined. The dependence of ΔG0on styrene content as well as on the composition of the solvent mixture and the temperature, shows that theunchargedpolyelectrolyte chains assume a compact conformation (globule) stabilized by hydrophobic interactions of maximum strength.Rough considerations on the electrostatic free energy of the macroion indicate that the dimensions of the compact form increase between α=0 and the transition point, so that the “globule” does not participate in the conformational change. It is suggested that this latter occurs in a one‐dimensional system, depending on the interaction of neighbori

ISSN:0025-116X    

DOI:10.1002/macp.1976.021770105

出版商:Hüthig&Wepf Verlag    

年代:1976

数据来源: WILEY

摘要:

AbstractThiol/dimethyl sulfoxide systems are good initiators for the polymerization of methyl methacrylate (MMA) and some other acrylate monomers in benzene medium, but they fail to initiate the polymerization of styrene, vinyl acetate and acrylonitrile. The rate of polymerization of MMA is dependent on the chain length of the thiol used and dodecanethiol is found to be the most reactive one. The presence of traces of oxygen increases the rate of polymerization probably by forming a co‐redox system with the thiol. The polymerization is completely inhibited by 2,2‐diphenyl‐1‐picrylhydrazyl and benzoquinone indicating the free radical nature of the reaction.The effect of butanethiol as well as that of dimethyl sulfoxide (DMSO) individually on the AIBN‐catalysed polymerization of MMA in benzene medium was examined. Butanethiol does not affect the rate of the radical polymerization, but reduces the molecular weight of the polymers formed due to a chain transfer. DMSO has no effect on the radical polymerization up to a concentration of 6,42.10−2mol 1−1, above which it reduces the rate and also the molecular weight probably by forming a growing radical‐DMSO adduct of a reactivity lower than that of the original g

ISSN:0025-116X    

DOI:10.1002/macp.1976.021770106

出版商:Hüthig&Wepf Verlag    

年代:1976

数据来源: WILEY

摘要:

AbstractThe kinetics of butanethiol/dimethylsulfoxide (DMSO) initiated polymerization of methyl methacrylate in benzene medium was studied gravimetrically. The thiol acts as the reducing component of the initiator system and also as a transfer agent. The order with respect to [Butanethiol] is 0,48. In the lower concentration region between 4,69.10−4and 9,38.10−2mol 1−1, DMSO behaves simply as the oxidant of the initiator system, and the rate of polymerization has the usual square root dependence on [DMSO]. But above the concentration of 9,38.10−2mol 1−1and up to 1,40mol 1−1, DMSO acts both as an oxidizing agent and as a retarder, forming an adduct with the growing radicals, which propagates the reaction with a retarded rate. The order with respect to monomer concentration is 1,04, when DMSO is used in the lower concentration range and it increases to 1,25 when [DMSO] is higher than 9,38.10−2mol 1−1. Thiols of different structures affect the rate significantly. The rate of polymerization is also dependent on the polarity and viscosity of the solvent being a maximum in benzene and a minimum in ethyl acetate. The efficiency of initiation of the initiator system is 60–80% and the overall activation energy is 72,45 kJ mol−1. An appropriate kinetic expression was derived to

ISSN:0025-116X    

DOI:10.1002/macp.1976.021770107

出版商:Hüthig&Wepf Verlag    

年代:1976

数据来源: WILEY

摘要:

AbstractA radical mechanism is proposed for the formation of the 1,2‐polymer2in the “spontaneous” polymerization of 4‐vinylpyridinium salts 4‐VP.HX (X=NO3, ClO4, HSO4, I) in aqueous solution on the basis of strong inhibition by oxygen and other radical inhibitors.Quantitative investigation of the influence of oxygen on the formation of the 1,2‐polymer allowed the derivation of a formal kinetic scheme for the initiation and polymerization steps which is consistent with a free radical mechanism. Dependence of the average molecular weight of2on monomer concentration is in agreement with this model. Dependence of the inhibition time on the oxygen concentration as well as an acceleration of the final polymerization rate by prolonged treatment of the monomer solution with oxygen suggests the transitory involvement of polymeri

ISSN:0025-116X    

DOI:10.1002/macp.1976.021770108

出版商:Hüthig&Wepf Verlag    

年代:1976

数据来源: WILEY

摘要:

AbstractThe kinetics of the degradation of cellulose triacetate in chloroform/acetic anhydride mixtures containing a perchloric or sulphuric acid catalyst was studied. The change in molecular weight with time was followed viscometrically, employing Maron's singlepoint method to evaluate limiting viscosity number values and using appropriate Mark‐Houwink constants for the chloroform/acetic anhydride mixtures. The dependence of the first‐order rate constant on concentration of catalyst, acetic anhydride, and cellulose triacetate, as well as polymer molecular weight and temperature was investigated. An explanation of the results, based on both H+and Ac+(acetylium ion) acting as the catalytic degradation species, is given; this is also shown to account for the degradation behaviour in similar cellulose acetate systems observed by previous work

ISSN:0025-116X    

DOI:10.1002/macp.1976.021770109

出版商:Hüthig&Wepf Verlag    

年代:1976

数据来源: WILEY

摘要:

AbstractEs wurden die scheinbaren kinetischen Parameter der thermischen und thermooxidativen Abbaureaktionen von Polyäthylenterephthalat für nicht‐isotherme Bedingungen bestimmt und die Abhängigkeit dieser Werte von der Aufheizgeschwindigkeit, dem mittleren Molekulargewicht und vom Umsatzgrad festgestellt. Es wurde gefunden, daß der Abbau in Stickstoff nach einem einheitlichen Kettenmechanismus mit kurzen kinetischen Ketten erfolgt, wogegen sich in Luft der Kettenabbaureaktion Oxidationsprozesse überlagern, bemerkbar an einem exothermen Ausschlag der DTA

ISSN:0025-116X    

DOI:10.1002/macp.1976.021770110

出版商:Hüthig&Wepf Verlag    

年代:1976

数据来源: WILEY