摘要:

AbstractThe kinetics of acrylonitrile polymerisation initiated by the redox system V(V)‐ethylene glycol were investigated in aqueous sulfuric acid in the temperature range 40–50°C. The rate of polymerisation, of V(V) disappearance, and the chain lengths of polyacrylonitrile were measured. The effect of certain water miscible organic solvents and certain neutral salts on the rate of polymerisation was investigated. The kinetics are consistent with the formation of an intermediate complex between the diol and the oxidant whose decomposition leads to the initiating radical. A suitable kinetic scheme is proposed and the various rate and energy parameters are comp

ISSN:0025-116X    

DOI:10.1002/macp.1977.021781101

出版商:Hüthig&Wepf Verlag    

年代:1977

数据来源: WILEY

摘要:

AbstractThe polymerization ofN‐tert‐butylaziridine (TBA) in dichloromethane with different cationic initiators leads to quantitative conversion. With triethyloxonium tetrafluoroborate (TEFB), initiation is rapid and the molecular weights of the polymers increase with increasing [TBA]/[TEFB]ratios. In contrast with other polymerizations ofN‐substituted aziridines, termination reactions are absent. This is ascribed to the high steric hindrance of thetert‐butyl group which makes a nucleophilic attack of a polymeric amino function on the growing species (aziridinium ion) impossible. Poly(TBA) obtained by precipitation from its solution shows a high degree of crystallinity as is shown by its mp of 142°C (DSC) and by its well resolved X‐ray diffraction diagram. The viscosities of aqueous solutions of the hydrochloride of poly(TBA) show typical polyelectrolyte

ISSN:0025-116X    

DOI:10.1002/macp.1977.021781102

出版商:Hüthig&Wepf Verlag    

年代:1977

数据来源: WILEY

摘要:

AbstractIn order to study the radical reactivities of trichlorophosphine, dichloro(phenyl)phosphine, and chlorodiphenylphosphine, the polymerizations of various vinyl monomers were carried out in the presence of these chlorophosphines using 2,2′‐azodiisobutyronitrile as an initiator. The reactivities were discussed from the results obtained for the rates and the degrees of polymerization and for the phosphorus contents of the polymers obtained. It was found that the tertiary radicals (such as that derived from methacrylonitrile and methyl methacrylate) were inert to these chlorophosphines, but the secondary radicals (such as those from vinyl acetate, methylacrylate, acrylonitrile, styrene, etc.) reacted with the chlorophosphines, and their reactivities depended on the stabilities of the polymer radicals. Only styrene gave copolymers. As a general mechanism the addition of the polymer radical to the phosphine followed by elimination of one of the four substituents on the phosphorus, was sugges

ISSN:0025-116X    

DOI:10.1002/macp.1977.021781103

出版商:Hüthig&Wepf Verlag    

年代:1977

数据来源: WILEY

摘要:

AbstractThe kinetics of the early stage of acid catalyzed heterogeneous hydrolysis of different samples of regenerated cellulose at low temperatures (0, 20, and 30°C) was studied. The degradation of macromolecules was followed by determining the decrease of the degree of polymerization by measuring the viscosity of cellulose solutions in cadoxen. Interpretation of the experimental results using equations for first order reactions showed that in the studied experimental range first order kinetics cannot be applied. It was found that the rate constant decreases during the course of the hydrolysis at constant temperature. However, the experimental results could be explained by kinetic equations for heterogeneous processes with a solid and a liquid phase in the heterogeneous system. Kinetic parameters calculated from these equations point out that the process could be described as a diffusion controlled process

ISSN:0025-116X    

DOI:10.1002/macp.1977.021781104

出版商:Hüthig&Wepf Verlag    

年代:1977

数据来源: WILEY

摘要:

AbstractThe 4π + 2π‐Diels‐Alder cycloadduct1involved in the spontaneous polymerization of styrene was investigated under conditions, where bimolecular reactions with styrene leading to a consumption of1can be neglected. For this reason1was (a) submitted to thermolysis in an inert solvent (toluene) at different temperatures (90, 100 and 110°C) and (b) oxidized with an excess of oxygen in styrene at room temperature. The reactions were followed spectrometrically at the wavelength λ = 325 nm and analyzed in terms of a first order reaction. The results show strong evidence for the involvement of two diastereomers (1aand1b) of different reactivity. This is in qualitative and quantitative agreement with the two isomers' concept, which had been deduced previously from kinetic analysis of the formation of1during the thermal polymerization of styrene. Rate constants and activation energies as well as possible reaction pathways ar

ISSN:0025-116X    

DOI:10.1002/macp.1977.021781105

出版商:Hüthig&Wepf Verlag    

年代:1977

数据来源: WILEY

摘要:

AbstractIt was found that the rate of secondary photooxidation reactions initiated by light not absorbed by polystyrene (PS) is related to the concentration of carbonyl compounds produced initially in pure PS films. Photochemical experiments carried out with a group of twelve low‐molecular‐weight compounds as models of the most likely carbonyl products of PS photooxidation showed that mainly diketones sensibilize the long‐wave UV photooxidation of polyst

ISSN:0025-116X    

DOI:10.1002/macp.1977.021781106

出版商:Hüthig&Wepf Verlag    

年代:1977

数据来源: WILEY

摘要:

AbstractA new pressure controlled twin‐ebulliometer without Cottrellpump is described. The apparatus is equipped with rotating vessels to establish complete equilibrium between liquid and vapour. The boiling temperature can be chosen by reducing the pressure by means of a pressure regulator in the range of 100–760 Torr.In SI‐Einheiten: 1 Torr=133,322 N/m2.The elevation of the boiling‐point is measured by two thermistors in a Wheatstone bridge circuit.Investigation of benzil and biphenyl in dilute benzene solution shows that the rotating ebulliometer permits operations within a boiling temperature range of 30–80°C.Measurements of polystyrene and poly(ethylene glycol) [poly(oxyethylene)] in benzene solution show that the rotating boiling vessel avoids the formation of foam. Therefore, the elevation of the boiling‐point of solutions of polymeric samples can be measured with th

ISSN:0025-116X    

DOI:10.1002/macp.1977.021781107

出版商:Hüthig&Wepf Verlag    

年代:1977

数据来源: WILEY

摘要:

AbstractStyrylpyridinium substituted vinyl polymers (6), which are in effect polymeric dyes, may easily be prepared by condensing poly[1‐(1,6‐dimethylpyridinium‐3‐yl)ethylene methyl sulfate] (3) with various aromatic aldehydes (5) using piperidine as catalyst. The preparation of 40 of these polymers prepared from 39 different aldehydes or combinations of them is reported. The spectral data show that they may be designed for maximum absorption almost anywhere from 270–540 nm and with a great variation in photosensitivity and solubility. It is possible to prepare the vinyl substituted styrylpyridinium salts and then polymerize them, or to prepare the styrylpyridine substituted vinyl polymer and then quaternize it, but the preferred method is to prepare the quaternized polymer3and then condense it with an aromatic aldehyde5to form the styrylpyridinium substituted vinyl polymer6. These polymers do not require spectral sensitization and, in fact, we found no compounds that act as se

ISSN:0025-116X    

DOI:10.1002/macp.1977.021781108

出版商:Hüthig&Wepf Verlag    

年代:1977

数据来源: WILEY

摘要:

AbstractThe kinetic and thermal parameters for the decomposition of 1,1′‐diacetoxy‐1,1′‐diphenylazoethane were determined using differential scanning calorimetry (DSC). The activation energy for decomposition is 145,1 kJ/mol, the heat of decomposition is −231,6 kJ/mol, and the rate constant (kdin s−1) obeys the relation inkd= 40,43 − (17460 K/T). This compound was used as initiator for the bulk polymerization of vinyl acetate. The polymerization was studied at 50, 55, 60, and 65°C. The rate of polymerization was followed dilatometrically. The per cent shrinkage was calculated from the partial specific volumes of polyvinyl acetate in vinyl acetate. The partial specific volumes were determined by means of an automatic digital densimeter. The number average of polymerization was obtained from viscosity data. The reaction order with respect to initiator concentration is smaller than 0,5 (between 0,27 and 0,31). The deviation is explained in terms of primary radical termination.The bulk polymerization of vinyl acetate at 65°C using both 1,1′‐diacetoxy‐1,1′‐diphenylazoethane and 2,2′‐azodiisobutyronitrile as initiators was also investigated by DSC technique. The data were used for obtai

ISSN:0025-116X    

DOI:10.1002/macp.1977.021781109

出版商:Hüthig&Wepf Verlag    

年代:1977

数据来源: WILEY

摘要:

AbstractThe structure of 1,3,3‐trimethyl‐1‐phenylbutyllithium (1b), which is a model compound for the active chain end in the polymerisation of α‐methylstyrene with butyllithium, was investigated with1H and13C NMR spectroscopy. The carbon‐13 chemical shift of the αC‐atom in benzene and tetrahydrofuran as solvent suggests a substantial sp2hybridisation. The rotation of the aromatic ring around the bond (C6H5)αC is hindered at room temperature. In benzene as solvent the carbon‐13 resonances of the αC‐atom and the aromatic C‐atoms are strongly broadened. This broadening, caused by exchange reactions or13C‐7Li‐coupling, can be interpreted by an interaction of the lithium atom with the aromatic ring. This interpretation of the13C NMR spectra leads to a structure, in which the lithium is not located at the αC‐atom but in the

ISSN:0025-116X    

DOI:10.1002/macp.1977.021781110

出版商:Hüthig&Wepf Verlag    

年代:1977

数据来源: WILEY