摘要:

AbstractThe capability of halogen displacement by metallic acetates in oxyhalomethylmethylsilanediyle units was studied on linear and cyclic model compounds and on homogeneous and heterogeneous polysiloxanes. By displacement of iodine oxyiodomethylmethylsilanediyle units were specifically and quantitatively transformed into acetoxymethylmethylsiloxane units. This displacement was found to be accompanied by rearrangement of siloxane linkages, however, cleavage of substituted methyl and of vinyl groups, as observed in the displacement of chlorine in oxychloromethylmethylsilanediyle units, was not observed.

ISSN:0025-116X    

DOI:10.1002/macp.1983.021840701

出版商:Hüthig&Wepf Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractProper reaction conditions were determined for the activation of water‐soluble, biocompatible poly[N‐(2‐hydroxypropyl)methacrylamide] (1) by esterification with 4‐nitrophenyl chloroformate (2). The rate constants of hydrolysis and aminolysis of the 4‐nitrophenyl ester groups in resulting polymer3were compared. It was shown that at pH 8 – 9 the rate of aminolysis in water solutions is high enough for binding bioactive molecules via NH2groups. Cobra venom acetylcholinesterase was bound to the activated polymer3and thermostability and immunogenicity of this product

ISSN:0025-116X    

DOI:10.1002/macp.1983.021840702

出版商:Hüthig&Wepf Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractThe amount of chymotrypsinogen linked to poly[N‐(2‐hydroxypropyl)methacrylamide], which was activated by cyanogen bromide, under various conditions was determined. The optimal activation time was found to be indicated by the beginning of an invariable base consumption during the reaction of the polymer with cyanogen bromide. The degree of activation increased with the concentration of cyanogen bromide and with the pH, and the yield of coupling can be increased by variation of the temperature, concentration of the reaction components, and pH. At room temperature and pH 9,3, the coupling reaction was completed in less than 24 h. The stability of the activated polymer depends strongly on temperature and pH. The analysis of the active moieties on the polymer carrier revealed that the application of the generally accepted mechanism for cyanogen bromide activation of polysaccharide carriers to the activation of poly[N‐(2‐hydroxypropyl)methacrylamide] remains to be

ISSN:0025-116X    

DOI:10.1002/macp.1983.021840703

出版商:Hüthig&Wepf Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractPrimary amine terminated polyisoprene2was produced by reaction of anionic living polyisoprene with one of the following protected aminating reagents:N‐(benzylidene)trimethylsilylamine (1a).N‐(1‐phenylpentylidene)trimethylsilylamine (1b),N‐benzylidenebenzenesulfeneamide (1c), orN,N‐bis(trimethylsilyl)‐2‐bromoethylamine (3). Especially with1a, the terminal amino group was quantitatively introduced at the end of the polymer chain.2was found to initiate the polymerization of theN‐carboxy anhydride of γ‐benzyl‐L‐glutamate5to afford poly(isoprene‐b

ISSN:0025-116X    

DOI:10.1002/macp.1983.021840704

出版商:Hüthig&Wepf Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractConstitutionally regular all‐ortho4‐tert‐butylphenol‐formaldehyde novolac resins were prepared free from cyclic compounds, by reaction of bromomagnesium 4‐tert‐butylphenoxide in aprotic nonpolar media with paraformaldehyde. Short syntheses of dinuclear to decanuclear methylene‐linked chain oligomers were also achieved via bromomagnesium ion‐assisted reaction of suitable phenolic precursors with paraformaldehyde or 5‐tert‐butyl‐2

ISSN:0025-116X    

DOI:10.1002/macp.1983.021840705

出版商:Hüthig&Wepf Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractMethyl methacrylate was copolymerized with butyl or isobutyl acrylates, and butyl, isobutyl, or 2,3‐epoxypropyl methacrylates, by hydrogen peroxide, in the presence of ethanol under UV irradiation (at 254 nm) at room temperature. The analysis of the microstructures was based on resonance splitting of the methoxy protons of MMA, depending on their environment. This splitting was not obtained with isobutyl and 2,3‐epoxypropyl methacrylates. All the products were found to be predominantly syndiotac

ISSN:0025-116X    

DOI:10.1002/macp.1983.021840706

出版商:Hüthig&Wepf Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractPolymerization of ethylene initiated in naphta solution by Zr(CH2C6H5)4at 200°C under high purity conditions showed a cocatalytic effect of water with a maximum rate for a mole ratio H2O/Zr close to 0,1. No activity was observed for the hypothetical compound (C6H5CH2)3ZrOZr(CH2C6H5)3. Ethylene polymerization was also initiated with supported catalysts obtained by reaction of Zr(CH2C6H5)4with silicium oxide or pre‐dried aluminium oxide with an increase of activity (by a factor of 5). The resulting polyethylenes were found to be virtually linear with 1,5 CH3groups for 1000 C atoms and with melting points of 134 – 136,5°C. They have high molecular weights with very broad distribution. These results were interpreted by a mechanism involving Ziegler‐like active

ISSN:0025-116X    

DOI:10.1002/macp.1983.021840707

出版商:Hüthig&Wepf Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractPolymerization of styrene in toluene solution at 50°C was found not to be initiated with sufficiently pure tetrabenzylzirconium or ‐titanium. However, a cocatalytic effect of water was observed with a maximum rate for a mole ratio H2O/Mt (Mt = Zr or Ti) close to 0,1. No activities were observed for the hypothetical compounds (C6H5CH2)3Mt—O—Mt(CH2C6H5)3. This cocatalytic effect was also observed with tribenzylchlorozirconium (1), tribenzylzirconiooxytriphenylsilane (2), or 6,6‐dibenzyl‐2,2,4,4‐tetramethyl‐1,3,5‐trioxa‐2,4‐disila‐6‐zirconacyclohexane (3). Styrene polymerizations were also initiated by supported catalysts obtained by reaction of Zr(CH2C6H5)4with aluminium oxide or silicium oxide pre‐dried at various temperatures. The activities of such systems were equal or slightly lower than those obtained with the system Zr(CH2C6H5)4/H2O (mole ratio 10 : 1). The resulting polystyrenes have very high molecular weights with very broad distribution. Copolymerization experiments with methyl methacrylate gave as main product a copolymer containing only 4% of monomeric units of styrene. A discussion of all results led to the conclusion that the main polymerization involves a

ISSN:0025-116X    

DOI:10.1002/macp.1983.021840708

出版商:Hüthig&Wepf Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractPolymerizations of L‐phenylalanine‐N‐carobxyanhydride(L‐Phe‐NCA) were conducted under various reaction conditions and the secondary structure of the resulting solid poly(L‐phenylalanine)s was examined by means of 50,3 or 75,4 MHz13C NMR CP/MAS spectra. When primary alkylamines were used as initiators only α‐helix contents ≤ 60% were obtained regardless of solvent and temperature. However, a part of the β‐sheet structures was thermodynamically unstable and could be converted into α‐helices by reprecipitation. An α‐helix content>90% was achieved only when weakly nucleophilic reagents, such as aromatic amines or water, were used as initiators in methylene chloride. A kinetic explanation of these results is discussed. Aprotic bases gave low yields of poly(L‐phenylalanine) and substantial amounts of low molecular weight side products. An α‐helix content ≥ 95%, was achieved when L‐Phe‐NCA was polymerized in pyridine at 100°C. The usefulness of IR spectra for the characterization of the secondary structure

ISSN:0025-116X    

DOI:10.1002/macp.1983.021840709

出版商:Hüthig&Wepf Verlag    

年代:1983

数据来源: WILEY

摘要:

AbstractThe polymerization of methyl methacrylate (MMA) in DMF with “aged” chromium (II) acetate (Cr(Ac2)) and benzoyl peroxide (BPO), previously formulated as a living radical polymerization, was investigated. The reaction between Cr(Ac)2and BPO gives besides N‐methylformamidomethyl benzoate (3) theN‐methylformamidomethylchromium(III) cation (6) as intermediate, which itself may react with BPO with the formation of additional free radicals as compared with the thermolysis of BPO. Thus, the polymerization of MMA in this system could be shown to be a normal radical one with free and uncomplexed radicals. The increase of the degree of polymerization with aging and monomer conversion is explained by the decreasing rate of the radical forming reactions and the onset of the gel

ISSN:0025-116X    

DOI:10.1002/macp.1983.021840710

出版商:Hüthig&Wepf Verlag    

年代:1983

数据来源: WILEY