摘要:

AbstractThe initiation reaction of the cationic polymerization of 3,3‐dimethylthietane by trityl hexafluoroantimonate occurs by a fast and quantitative direct addition of the trityl cation to the sulfide function thus producing the corresponding polymer with tritylthio head‐groups. In contrast with this mechanism, the reaction of the trityl salt with the non‐polymerizable sulfides tetrahydrothiophene and diethyl sulfide, leads to a slow hydride abstraction from the sulfide. With these sulfides an equilibrium [carbenium ion + sulfide ⇌ sulfonium ion] is also observed. At 25°C the association constants were found to be 2,27 and 0,096 1 · mol−1for tetrahydrothiophene and diethyl sulfide, respectively (in CD2Cl2). The initiation mechanism by sulfonium ion formation is explained by the high reactivity of the formed four‐membered ring trityl sulfonium ion which disturbs the carbenium ion‐sulfonium ion equilibrium and ultimately leads to quantita

ISSN:0025-116X    

DOI:10.1002/macp.1981.021821201

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractThe cyclic oligomers which are formed during the cationic copolymerization of oxetane (1) with 3,3‐dimethyloxetane (2) were analyzed qualitatively and quantitatively by means of gas chromatography and mass spectroscopy. Cyclic oligomers from trimer up to octamer were detected but, as with the homopolymerizations, the cyclic tetramers were the most abundant. The relative abundances of the different tetramer co‐oligomers were compared with the theoretical abundances, calculated from the reactivity parameters of the copolymerization and the monomer feed ratio, using the method of Ito and Yamashita. There was no agreement between the calculated and experimental values. This was attributed to a lower tendency to cyclize for polymer chains having a2‐oxonium chain end compared with polymer chains having a1‐oxonium ch

ISSN:0025-116X    

DOI:10.1002/macp.1981.021821202

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractPolychelates of Ni(II), Co(II), Cu(II), Zn(II), and Mn(II) were synthesized from bis 4,4′‐(4,4′‐biphenylenebisazo)di(salicylaldehyde oxime) and metal chlorides. All the chelates are dark in colour and insoluble in common organic solvents. Their most probable structures were determined by visible reflectance spectroscopy and magnetic measurements in conjunction with thermogravimetric and IR measurements. Elemental analyses indicate a ligand: metal ratio of 1:1 and the association of water molecules with the central metal. The decomposition temperatures of the polychelates decrease in the following order: Zn(II)>Co(II)>Ni(II)>Mn(II)

ISSN:0025-116X    

DOI:10.1002/macp.1981.021821203

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractChlorides of carboxylic acids were grafted on telomers of vinyl alcohol. The yields of grafting were improved by increasing the temperature and the concentration of the reactants. In the range investigated, they do not depend on theDPnof the telomers, nor on the stoichiometric rates of the reactants. Therefore, the grafting rates are directly related to the initial conditions of the reaction. Modification of the telomers by treatment with ethylene oxide provides more soluble substances, but it does not affect the behaviour of the telomers in grafting reactions. Grafting of 1‐(p‐chlorobenzoyl)‐5‐methoxy‐2‐methyl‐3‐indolacetic acid (9) (indomethacin), an antiinflammatory drug, leads to potentially pharmacologically

ISSN:0025-116X    

DOI:10.1002/macp.1981.021821204

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractChloropyrimidine derivatives were found to be useful as active dehydrating and desulfhydrylating reagents for the preparation of carbodiimides, isothiocyanates, esters, lactones, amides, or nitriles. Particularly a polystyrene‐bound reagent was quite useful also due to the advantage of isolating the products easily by using a simple filtration technique. The following decreasing order of reactivity was found: 4‐chloro‐2‐pyrimidone bound to polystyrene (poly{1‐[4‐(4‐chloro‐2‐oxo‐1,2‐dihydro‐1‐pyrimidinyl)phenyl]ethylene}) (5a) ≃ 4‐chloro‐1‐cyclohexyl‐2‐pyrimidone (3a)>2,4,6‐trichloropyrimidine (2a)>2,4‐dichloropyrimidine (1a) ≫ 9‐benzyl‐6‐chloropurine (4a). The reactivities are related to the structure, and an enhanced ease of lactim‐lactam tautomerism in the pro

ISSN:0025-116X    

DOI:10.1002/macp.1981.021821205

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractBy means of the strong base sodiumtert‐butoxidep‐tolylaldehyde (1a), 5‐methyl‐2‐thiophene carboxaldehyde (1b), and 5‐methyl‐2‐furancarboxaldehyde (1c) can be polycondensed in dimethylformamide to give poly(1,4‐phenylenevinylene) (2a), poly(2,5‐thiophenediylvinylene) (2b), and poly(2,5‐furandiylvinylene) (2c).2aand2bare also available from the Schiff's bases of1aand1b. The polymers are identical with polymers synthesized via the Wittig reaction. The vinylene units have t

ISSN:0025-116X    

DOI:10.1002/macp.1981.021821206

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractFrom 2,3,5,6‐tetramethylthiazolo[4,5‐f]benzothiazoldiium diperchlorate (9) and the ortho esters2a–dor 1,1,3,3‐tetramethoxypropane (4) polymeric cyanines with trimethine (10a), substituted trimethine (10b–d), respectively pentamethine units (11) were synthesized. Model compounds (3a–e,5,7a–d,8) were prepared from1a,1band6, analogously. The structures were confirmed by elemental analyses, IR, and electronic spectra. In addition, the model compounds were characterized by their1H NMR and

ISSN:0025-116X    

DOI:10.1002/macp.1981.021821207

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractAn equipment for measuring the photoconduction of polymeric material is described comprehensively. The electrical dark conductivities (σ ≤ 2,5 · 10−9Ω−1· cm−1) and the photoconduction (Iphot≤ 2,0 · 10−10A) were studied for polymeric cyanines and corresponding model compounds. Photoconduction was measured as a function of temperature, current, wavelength, and intensity o

ISSN:0025-116X    

DOI:10.1002/macp.1981.021821208

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractIt was shown that radical polymerization of butadiene in 1‐butanol and 2‐butanol, initiated by hydrogen peroxide cleaved into two hydroxyl radicals by heat, leads to three types of polymers according to their respective polydispersity. It was found that the formation of these products — oligomers, polymers, and high polymers — can be influenced by modifying the experimental conditions. Thus, it is possible to obtain selectively oligomers free of polymers and polymers free of low molecular weight ol

ISSN:0025-116X    

DOI:10.1002/macp.1981.021821209

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractPhotothermal and TiO2‐ or ZnO‐photocatalyzed oxidations of type B‐ and type K‐polyundecanamides (RILSAN) were studied analytically and kinetically. IR spectrophotometry and chemical titration showed that hydroperoxy groups in the polymer reach a fairly high photostationary concentration. Then the primary photoproductsAdecompose into products with imido groups (C), the concentration of which are increasing until a photostationary value. Under irradiation, the imidesCare converted into acids and amides; in thermooxidation acids are the main products. The intermediate products in photocatalysed oxidation were found to be the same as in photochemical oxidation; a photochemical protection of hydroperoxides and imides was observed, due to the inner filter effect of the absorbing pigments. It could be shown that in polychromatic light the photocatalytic activity of TiO2(rutile) is more important than its inner filter effect; this antagonism does not depend on the concentration of the photoactive

ISSN:0025-116X    

DOI:10.1002/macp.1981.021821210

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY