摘要:

AbstractThe role of Ti3+ions in titanium‐magnesium catalysts of various composition, TiCl4/MgCl2+ AlR3, TiCl4/MgCl2+ Al(i‐Bu)3+ EB, TiCl4/EB/MgCl2+ Al(i‐Bu)3and TiCl4/EB/MgCl2+ Al(i‐Bu)3+ EB, was studied by means of ESR. The ESR data and the catalytic properties were compared. It could be shown that the introduction of ethyl benzoate (EB) leads to an increase of stereospecificity, to a considerable increase of the portion of Ti3+ions which can be observed by ESR, to the appearance of several new signals in the ESR spectra and to an increase of the portion of titanium in solution, removed from the solid catalyst during the interaction with the organoaluminium cocatalyst. Titanium ions are found mainly in the particles or surface associates whose Ti3+ions produce no signals in the ESR spectra, Ti3+ions observed by ESR are found to be inactive centers of polymerization. The active centers appear to be localized in highly dispersed particles or surface associates of TiCl3, formed on the MgCl2surface and are not revealed in the ESR spectra. Increasing stereospecificity in the presence of EB is assumed to be caused by deactivation of non‐stereospecific active centers with ethyl

ISSN:0025-116X    

DOI:10.1002/macp.1986.021870201

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe kinetics of the polymerization of acrylamide initiated by potassium peroxodisulfate in aqueous medium is studied in the presence of poly(butyl acrylate) latex. The rate of acrylamide polymerization increases with the concentration of the latex in the reaction system. The increase is especially pronounced at concentrations of solid latex higher than 100 g per dm3of polymerization mixture. The activation energy of the acrylamide polymerization in the presence of poly(butyl acrylate) latex is 85,8 kJ · mol−1. This value is substantially higher than the value of 70,7 kJ · mol−1found for the activation energy of the polymerization of acrylamide in the absence of poly(butyl acrylate) latex. A set of reactions is proposed and the equation describing the simultaneous homopolymerization of acrylamide and grafting of poly(butyl acrylate) latex with acrylamide is de

ISSN:0025-116X    

DOI:10.1002/macp.1986.021870202

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe acylated β‐cyclodextrins, heptakis(2,3,6‐tri‐O‐acetyl)‐β‐cyclodextrin, heptakis(2,3,6‐tri‐O‐obutyryl)‐β‐cyclodextrin, heptakis(2,3,6‐tri‐O‐butyryl)‐β‐cyclodextrin, and heptakis(2,3,6‐tri‐O‐pivaloyl)‐β‐cyclodextrin, cause a marked increase in the rate of polymerization of water‐ soluble vinyl monomers using water insoluble initiators in the two‐phase system consisting of water and an organic solvent (chloroform/ligroin, volume ratio 1 : 4). A plausible mechanism for this polymerization is proposed: The lipophilic acylated cyclodextrin acts as an initiator carrrier from the organic to

ISSN:0025-116X    

DOI:10.1002/macp.1986.021870203

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractFrom 1‐chloro‐2,3‐epoxypropane (epichlorohydrin), soluble poly(epichlorohydrin)s were prepared with molar masses in the range of 3,7 · 104to 1,7 · 105g/mol, using a complex of epichlorohydrin with hexaamminecalcium. These poly(epichlorohydrin)s were modified by reaction with 2‐mercaptoethanol or thioglycolic acid. The yields of these reactions range between 40 and 60%. The drop of molecular weight due to modification oscillate between 3,8 and 48,1%. The structure of the modified polymers was confirmed by elemental analyses, thermogravimetric and mass spectroscopic investigations. These chemical modifications carried out with poly(epichlorohydrin)s lead to water‐solub

ISSN:0025-116X    

DOI:10.1002/macp.1986.021870204

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe reaction of 2,4,5‐trisubstituted 1,3‐dioxolan‐2‐ylium salts with 1,3‐dioxolane results in the formation of the more reactive 1,3‐dioxolan‐2‐ylium salts monosubstituted in 2‐position and 4,5‐dimethyl‐1,3‐dioxolane. Values of the rate constants of this reversible reaction, which is supposed to precede the actual initiation process in the polymerization of 1,3‐dioxolane by trisubstituted dioxolenium salts, depend on the structure of the dioxolenium cations. Steric hindrances and positive charge delocalization effects due to the substituents in dioxolenium cations were found to reduce the rate of that reversible reaction. Thetrans‐isomers are less reactive than the respectivecis‐isomers, while aromatic derivatives are less reactive than thos

ISSN:0025-116X    

DOI:10.1002/macp.1986.021870205

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractA new class of mesogenic α,ω‐alkylene bis[4‐(4‐acryloyloxybenzoyloxy)benzoate]s1a — 1gwere synthesized and studied for their mesophase behaviour. The thermodynamic parameters of the isotropization transitionTi, ΔHiand ΔSishow distinct odd‐even alternations and demonstrate that the thermotropic liquid crystalline properties in homologous series of mesogens can not be a continuous function of the length of the inner spacer segment. It is anticipated that the investigated diacrylates are of value as precursors of thermotropic semiflexible polymers, crosslinking agents for mesomorphic polymer networks and low molecular weight twin mo

ISSN:0025-116X    

DOI:10.1002/macp.1986.021870206

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractAn alternating copolymer of 1‐vinyl‐2‐pyrrolidone and maleic anhydride,14C‐labelled at the chain end, was synthetized with a mass‐average relative molecular massM̄w= 8000. Elimination kinetics and whole‐body distribution of the copolymer in its monosodium salt form were studied in mice. Elimination of the copolymer was found to be fairly rapid and practically complete, i.e. 86,7% of it was excreted after 24 h and 95% after 56 h. Specific accumulation of the copolymer was observed in bone tissue and lacrimal gland. No appreciable accumulation occurred in the nervous system, spleen, and bone marrow. The results of elimination kinetics and the autoradiographic whole‐body distribution study were in fairly go

ISSN:0025-116X    

DOI:10.1002/macp.1986.021870207

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe process of chymotrypsin catalysed hydrolysis of L‐phenylalanyl‐4‐nitroanilide (Phe‐NNp) residues bound via 6‐aminohexanoic acid (ϵ‐Ahx) spacer to the polyanionic carrier, poly(N‐vinylpyrrolidone‐co‐maleic acid), was studied. The initial rate of hydrolysis was measured at pH 8 as a function of mole ratio of side chains (‐ϵ‐Ahx‐Phe‐NNp) randomly distributed along the backbone. The polyanionic carrier studied shows a pronounced effect on the process, as overall kinetic parameters (kcatandKm) of ‐ϵ‐Ahx‐Phe‐NNp, attached to the polymer, differsignificantly from the respective values of the low‐molecular‐weight substrate analogue, succinyl‐ϵ‐Ahx‐Phe‐NNp. Relationship between the side chain content and thekcat/Kmvalues, examined in the range of 1 to 20 mol‐%, exhibits a saturation‐profile. The limiting value ofkcat/Km(5 · 1031 · mol−1· s−1) appeared to be as much as 8‐times higher than that of succinyl‐ϵ‐Ahx‐Phe‐NNp. The course of chymotrypsin catalysed hydrolysis of the polymer‐substrate bearing 20 mol‐% of side chains shows first order kinetics, with the conversion approaching asymptotically 100%. pH dependence of the maximum velocity of hydrolysis (Vm), determined in the range 5–10, shows a maximum

ISSN:0025-116X    

DOI:10.1002/macp.1986.021870208

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

Abstract10‐(11‐Methacryloyloxyundecyloxycarbonyl)decyl 2‐(trimethylammonio)ethyl phosphate was prepared, characterized, and polymerized with 2,2′‐azoisobutyronitrile (AIBN). The polymer exhibits liquid crystalline behaviour from room temperature up to ca. 280°C and is soluble in methanol and h

ISSN:0025-116X    

DOI:10.1002/macp.1986.021870209

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractPolysaccharides having β‐glycosidically linked D‐glucose branches were synthesized by condensation of 3,4,6‐tri‐O‐acetyl‐(1,2‐O‐ethylorthoacetyl)‐α‐D‐glucopyranose with activated curdlan (β‐(1→3)‐glucan) and its acetyl derivatives in boiling chlorobenzene in the presence of catalytic amounts of 2,6‐dimethylpyridinium perchlorate. The branched polysaccharides were converted into water‐soluble polysaccharides by saponification and then tested for their antitumor activity. Branched polysaccharides synthesized from unsubstituted curdlan with 60% or more branching and those from curdlan acetate with 30% or more branching are completely soluble in water. The structure of branched polysaccharides obtained from curdlan was determined from methylation analysis, and it was found that branching occurs preferentially at the C‐6 positions by β‐glycosidic linkages. Some of the synthesized branched polysaccharides with high molecu

ISSN:0025-116X    

DOI:10.1002/macp.1986.021870210

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY