摘要:

AbstractThe alkaline hydrolysis of polyacrylamide in solution is studied viscosimetrically. The viscosity of the solution increases continuously during the course of hydrolysis. The relationship between intrinsic viscosity and the extent of reaction is established, using a series of polyacrylamides with known extents of hydrolysis. The extent of reaction is determined from the observed flowtime, using the relationship between [η] and extent of reaction. The second‐order rate constant and the activation energy are in good agreement with those reported in the literature. A four‐fold increased reactivity of the amide groups towards hydrolysis is observed at very low extents of hydrol

ISSN:0025-116X    

DOI:10.1002/macp.1981.021820101

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractThe effects of temperature and solvents on the polycondensation of active β‐alanine 4‐acyl‐2‐nitrophenyl esters1a–g, having alkyl groups with different chain lengths, were studied. Nonpolar solvents were found to be well suited for the polycondensation, which was inhibited by the presence of a small amount of methanol. The reaction was found to be affected also by the temperature, the optimum temperature being 25°C. The results can be explained by assuming an aggregation of the active esters. This was checked with the model compounds3, 4aand4b, which correspond to the (dehydrobrominated) active ester1e. The apparent mean aggregation numbers of the model compounds were determined in cyclohexane and in methanol by an osmotic method. The results led to the suggestion that the aggregation plays an important role in the polyc

ISSN:0025-116X    

DOI:10.1002/macp.1981.021820102

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractA procedure for the preparation of a novel class of nitroaniline substituted diacetylene alcohols is reported. The polymerization behavior of one member of this class, 6‐(4‐nitro‐2‐trifluoromethylanilino)‐2,4‐hexadiyn‐1‐ol (11a), has been studied using X

ISSN:0025-116X    

DOI:10.1002/macp.1981.021820103

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractPolymerisation of acrylonitrile and methyl methacrylate initiated by the system cyanoacetic acid‐Mn(III)(acac)3is investigated in DMF and in DMSO at 25–35°C. Kinetics of reduction of the complex by cyanoacetic acid shows the formation of a mixed ligand complex whose decomposition yields the primary radicals. Efficient initiation of polymerisation by these radicals followed by exclusive mutual termination accounts for the kinetics of polymerisation. Rate and equilibrium parameters are evaluated and their significance discu

ISSN:0025-116X    

DOI:10.1002/macp.1981.021820104

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractPolymerisation of acrylonitrile initiated by the redox systems glycerol‐Mn(III) and allyl alcohol‐Mn(III) is investigated in the temperature range 25–45°C in aqueous sulfuric acid/acetic acid and aqueous sulfuric acid, respectively. Oxidation of both glycerol and allyl alcohol proceeds through an intermediate complex. Decomposition of the complex is reversible with glycerol, whereas with allyl alcohol it is irreversible. Addition of Mn(II) retards both oxidation and polymerisation in the former system, while with the latter oxidation in the absence of monomer is unaffected, although polymerisation rates are retarded. Mutual termination predominates with the system glycerol‐Mn(III), whereas primary radical termination accounts for the kinetics of polymerisation with the system Mn(III)‐allyl alcohol. Rate and equilibrium parameters are evaluated and their significance is

ISSN:0025-116X    

DOI:10.1002/macp.1981.021820105

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractCopolymerisation of styrene,p‐acetoxystyrene, and divinylbenzene is a convenient way of obtaining resins for application in solid phase peptide synthesis. Phenolic group attachment sites are readily obtained by hydrolysis under mild conditions of the acetoxyl resin. In order to investigate possible effects of lyophilic (e.g. amino acid) units attached to the resin on subsequent reactivity in peptide synthesis, the coupling efficiencies of initially prepared phenolic resins and equivalent resins already functionalised with the tripeptide, H‐Leu‐Ala‐Gly, have been compared in reactions with Boc‐Gly‐ONSu and Boc‐Ile‐OTcp. The two resin types afford phenolic and primary amino‐functionalities respectively and exhibit marked solvent effects on reactivities, although swelling characteristics are rather similar. It is concluded that solvent effects on the particular coupling reactions are more important than solvent effects on swell

ISSN:0025-116X    

DOI:10.1002/macp.1981.021820106

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

Abstractα‐Methylbenzylchloride (1) was polymerized in ethyl chloride and in 1‐nitropropane at various temperatures with AlCl3as catalyst, mainly at −115 and at 0°C. The polymers obtained were crystalline or amorphous, depending on the reaction conditions. The reactions were complete within seconds. The tacticity of the polymers was determined by1H and13C NMR‐spectroscopy. Polymers prepared at low temperatures in ethyl chloride showed isotactic sequences; in 1‐nitropropane at 0°C atactic configuration. A reaction mechanism for the formation of the isotactic polymer is proposed on the basis of GPC‐data. DSC‐data are report

ISSN:0025-116X    

DOI:10.1002/macp.1981.021820107

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractAromatic spiro polymers, polyoxoindoline‐spiro‐benzimidazolines9a–c, were prepared by the solution polycondensation reaction of biisatyls with aromatic tetramines in polar organic solvents. The spiro polymers were found to exhibit good solubility in polar organic solvents, such asN,N‐dimethylacetamide and hexamethylphosphoramide, in contrast to the insolubility of the corresponding polyindoloquinoxalines in these solvents. The improvement of the solubility was discussed mainly in terms of the hydrogen bonding and packing in polymer molecules. The spiro polymers slowly rearranged at high temperatures to give polyindoloquinoxalines with high thermal st

ISSN:0025-116X    

DOI:10.1002/macp.1981.021820108

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractPossible structures for the products obtained on alkali treatment of polyacrylonitrile are considered. The Pariser‐Parr‐Pople (PPP) self‐consistent field method was applied to give λmaxvalues for the proposed structures. The colouration of PAN by alkali was found to occur in two stages. There is a temporary colour which is destroyed by acids and a permanent colour which is not. The colour of alkali treated PMAN is entirely destroyed by acids. This temporary colouration may arise from n → π*transitions. We believe that the permanent colour of degraded PAN arises from π→π*transitions via a free radical activition mechanism and use of mol

ISSN:0025-116X    

DOI:10.1002/macp.1981.021820109

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractPolymer single crystals with a germanium backbone have been synthesized. The synthesis involves a thermally induced generation of divalent radicals, transport of these radicals and subsequent addition polymerization on a cold surface. The polymerization was carried out under vaccum. Crystallization during polymerization was found to occur resulting in extended chain macromolecular crystals. These crystals were prismatic with a number‐average molecular weight of 11300. The melting range of the\documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} ({\rm GePh}_2 \rlap{--})_{\rm n} $\end{document}crystals is 285 to 295°C. The glass transition temperature of the same polymer in its amorphous state was found to be 96°C (20°C/min heating rate using differential thermal analysis). The crystal structure of the intermediate octaphenylcyclotetragermane is compared to that of octaphenylcyclotetrasilane and polydiphenylgermy

ISSN:0025-116X    

DOI:10.1002/macp.1981.021820110

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY