摘要:

AbstractThe paper describes the syntheses of four asymmetric sorbents, which containS‐(2‐aminoethyl)‐L‐cysteine (1a),S‐(carboxymethyl)‐L‐cysteine (1c),S,S′‐(ethylene)‐bis(L‐cysteine) (2a), andN,N′‐(ethylene)‐bis(D‐methionine) (3a) groupings as the chiral fixed ligands in a cross‐linked polystyrene matrix. The sorbents were used for ligand‐exchange chromatography of amino acid enantiomers in the presence of Cu(II) and Ni(II) ions. Enantioselective effects in the formation of mixed‐ligand complexes consisting of a fixed ligand, a metal ion, and an amino acid enantiomer were determined. The highest values of enantioselectivity reaching 1 300 to 1 890J/mol were found in mixed‐ligand complexes conta

ISSN:0025-116X    

DOI:10.1002/macp.1978.021790901

出版商:Hüthig&Wepf Verlag    

年代:1978

数据来源: WILEY

摘要:

AbstractNumerous polyesters were prepared from 1,2‐ethanediol, 1,3‐propanediol, 1,4‐butanediol, 1,6‐hexanediol, 1,12‐dodecanediol, 1,4‐phenylenedimethanol, and hydroquinone on the one hand and succinyl chloride, glutaroyl chloride, adipoyl chloride, suberoyl chloride, sebacoyl chloride, isophthaloyl chloride, and tetephthalolyl chloride on the other hand. The13C NMR spectra of all polyesters were measured in trifluoroacetic acid and relationships between the structure of the monomeric units and the chemical shifts of the carbonyl and OCH2‐signals were established. Copolyesters were prepared either by cocondensation of two diacid dichlorides and two diols or by thermal transesterification of two homopolyesters. The13C NMR spectra allow one to distinguish copolyesters from mixtures of corresponding homopolyesters and they allow the determination of the length of hom

ISSN:0025-116X    

DOI:10.1002/macp.1978.021790902

出版商:Hüthig&Wepf Verlag    

年代:1978

数据来源: WILEY

摘要:

AbstractBy polymerisation of ethylene dimethacrylate with n‐butyllithium in solution reactive microgels have been obtained. These EDMA‐microgels are nearly spherical, have a broad distribution and are easily swellable in organic solvents. The macrogelation depends on the amount of solvent between the microgel partic

ISSN:0025-116X    

DOI:10.1002/macp.1978.021790903

出版商:Hüthig&Wepf Verlag    

年代:1978

数据来源: WILEY

摘要:

AbstractMolecular weights and structural characteristics of the polymers formed in the system isoprene/oligoisoprenyllithium (OILi)/N,N,N′,N′‐tetramethylethylenediamine (TMD)/hexane (mole ratio TMD/OILi‐0,01) at various conversions at −30°C were determined. The applied conditions made it possible to judge the relative activity of various types of growing chains. The results obtained suggest an opposite influence of the complex formation with respect to the associated and non‐associated organolithium compounds. It was found that the former are activated (in comparison to the non‐complexed associates), whereas the latter (in comparison to the non‐complexed monomeric forms MnLi) become less active by complex formation. The possible causes of this different behaviou

ISSN:0025-116X    

DOI:10.1002/macp.1978.021790904

出版商:Hüthig&Wepf Verlag    

年代:1978

数据来源: WILEY

摘要:

AbstractThe use of low molecular weight, bicyclic, and polymeric tetraaza[14]annulene metal complexes1–5of copper(II), cobalt(II), iron(II), and nickel(II) as oxygen activating catalysts in the oxidation of ethylbenzene to acetophenone was examined. In addition semiconducting properties and thermal stabilities of these complexes were investigate

ISSN:0025-116X    

DOI:10.1002/macp.1978.021790905

出版商:Hüthig&Wepf Verlag    

年代:1978

数据来源: WILEY

摘要:

AbstractThe copolymerization of ethylene with 1,3‐butadiene to give crystalline, homopolymer‐free, high molecular weight, substantially linear copolymer is described. Butadiene polimerizes almost exclusively in atrans‐1,4 structure, ranging in content from zero to 50 mole‐%. At relatively low content of butadiene monomeric units (≤30 mole‐%) X‐ray crystallinity is of polyethylene type with a slight variation of the structural parameters. At higher levels of butadiene monomeric units, crystallinity oftrans‐1,4‐polybutadiene is also observed. The products with little unsaturation (1–5 mole‐%) melt at about 132°C and are able to crosslink with sulfur‐based recipes. A13C NMR study shows a block‐type structure, but the copolymer appears homogeneous in composition. The product of the reactivity ratios was evaluated. The catalyst system consists of vanadium tris(acetylacetonate), diethylaluminium chloride, and an acidic compound or its precursor. The nature and the amount of the acidic modifier regulate the polymerization rate as well as the molecular weight, composition, and long branching of the copolymer, so that a strict control of the catalyst system is required. The behaviour of the catalyst is tentatively explained by the polarity of the active carbon‐vanadium bond, which depends on substi

ISSN:0025-116X    

DOI:10.1002/macp.1978.021790906

出版商:Hüthig&Wepf Verlag    

年代:1978

数据来源: WILEY

摘要:

AbstractThe principal structural characteristics of ethylene‐butadiene copolymers prepared with a modified vanadium catalyst are described. The distribution of the butadiene monomeric units, though non‐random, is sufficiently homogeneous at low monomeric units content of butadiene (1–3 mole‐%) that a ready and efficient vulcanization with sulfur based systems is easily achieved.Long chain branching, which has a detrimental effect on the copolymer properties, can be measured rheologically and controlled at a very low level by the catalyst system. Vulcanized ethylene‐butadiene copolymers show improved mechanical properties with respect to high density polyethylene and good processability befo

ISSN:0025-116X    

DOI:10.1002/macp.1978.021790907

出版商:Hüthig&Wepf Verlag    

年代:1978

数据来源: WILEY

摘要:

AbstractAmino acids containing uracil, adenine and imidazole residues were prepared and polymerized by reacting with phosgene in ethylene carbonate. The polymers did not have a simple polypeptidic structure but were soluble in aqueous dimethylformamide and interacted with complementary polynucleotides. Alternative polymerization of amino acids byN,N′‐carbonyldiimidazole in aqueous neutral buffers proceeded with very low conversion but pure polypeptides resulted from the reaction. The following amino acids were prepared: β‐adenin‐9‐yl‐α‐alanine (1a),N‐methyl‐β‐(adenin‐9‐yl)‐α‐alanine (1b), β‐(uracil‐1‐yl)‐α‐alanine, (2a),N‐methyl‐β‐(uracil‐1‐yl)‐α‐alanine (2b), β‐(5,6‐trimeth

ISSN:0025-116X    

DOI:10.1002/macp.1978.021790908

出版商:Hüthig&Wepf Verlag    

年代:1978

数据来源: WILEY

摘要:

AbstractThe kinetics of thermal degradation of poly(oxytetramethyleneoxyterephthaloyl) was studied. This polyester undergoes a pyrolysis reaction in the temperature range of processing via a statistical mechanism proceeding by a random scission of the carbon‐oxygen bondings. This phenomenon is characterized by an energy of activation of 189,2kJ/mol (45,2kcal·mol−1) and by a negative entropy of activation [−20,3J·mol−1·K−1(−4,84cal·mol−1·K−1)]. Like most of the esters with a hydrogen atom in β position, this polyester undergoes degradation by an intramolecular mechanism involving the formation of a cyclic transition state. The very high value of the degradation constant of this polycondensate is probably a result of the presence, in this chain, of the very flexible t

ISSN:0025-116X    

DOI:10.1002/macp.1978.021790909

出版商:Hüthig&Wepf Verlag    

年代:1978

数据来源: WILEY

摘要:

AbstractA reaction vessel automatically controlled by magnetic valves is described which allows kinetic measurements of reactions with half livest1/2≥2s by gravimetric determination of the conversion. Thus, it covers the gap between the flow tube and the conventional reaction vessel.The influence of mixing time and filling time on the molecular weight distribution of an anionically prepared polymer is discusse

ISSN:0025-116X    

DOI:10.1002/macp.1978.021790910

出版商:Hüthig&Wepf Verlag    

年代:1978

数据来源: WILEY