摘要:

AbstractPolymerization of styrene by perchloric and trifluoromethanesulfonic acids has been assumed previously to proceed via a pseudo‐cationic mechanism. We found that for the latter system the trifluoromethanesulfonate ester is not stable. Attempts to observe the model 1‐phenylethylester were unsuccessful even at −78°C. In the reaction between 1‐phenylethyl bromide and AgSO3CF3a very rapid alkylation of the aromatic rings occurs. In the reaction between 1‐phenylethanol and (CF3SO2)2O a very rapid reaction between the intermediate ester (or ion) and the alcohol leads to the formation of the corresponding ether. A reaction carried out with the optically active alcohol indicates that no more than 4% of the intermediate species might have reacted with the alcohol as ester before racemization (i.e. ionization). The macromolecular ester does not seem to be much more stable and in19F NMR spectra only the acid was observed. An attempt at the formation of a block copolymer withN‐tert‐butylaziridine give zero or very low yield, contrarily to results previously observed with perchloric acid. An analysis of some former results on polymerization kinetics and of the new data given in this paper show no real evidence in favor of the pseudo‐cationic polymerization of styrene in CH2Cl2, initiated by CF3SO3H. The various data may be explained more satisfactorily by a more classical ionic mechanism. Triflic acid can reversibly protonate olefins due to the affinity of the triflate anion being higher for a proton than for a secondary or tertiary carbon atom; this is sufficient to explain the extremely low concentration

ISSN:0025-116X    

DOI:10.1002/macp.1986.021871001

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractLiquid crystalline aromatic‐aliphatic polyetheresters with mesogenic groups of different isomeric structures and flexible oligo(oxyethylene) spacers in the backbone were synthesized and their properties were studied. The influence of the mesogenic group structure, spacer length and nature of bonds linking the mesogenic groups and the spacers, on the phase transition temperatures was elucidated. On the basis of optical textures, observed in the polarizing microscope, smectic or nematic melts were found to be present in the polymers studied, depending on the mesogenic group structur

ISSN:0025-116X    

DOI:10.1002/macp.1986.021871002

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe structure of telomers5a, b, prepared from 2,3‐epoxypropyl methacrylate (2) and benzenethiol (1a) or 1‐dodecanethiol (1b) by UV irradiation, was studied by MS, IR,1H and13C NMR spectroscopy. The IR spectra of the products show that thiol addition occurs only at the double bond of monomer2. Mono‐ and diadducts could be isolated by fractionation and were characterized spectroscopically together with higher telomers (10

ISSN:0025-116X    

DOI:10.1002/macp.1986.021871003

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe polymerization of 3‐chloro‐2‐methyl‐1‐propene was investigated at temperatures between 0 and −80°C, using AlCl3and AlBr3as initiators. The molecular weights of the resulting oily products depend on the polymerization temperature and varied in the range of the number‐average molecular weightM̄n= 400–620. The course of polymerization was studied and the characteristic groupings in the oligomeris were identified by means of1H NMR and13C NMR spectroscopy. Based on the results the mechanism of partial reactions was discussed to explain the new type of propagation in the cation

ISSN:0025-116X    

DOI:10.1002/macp.1986.021871004

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractPolyurethanes were synthesized from 4,4′‐[1,4‐phenylenebis(methylidynenitrilo)]diphenylethanol (3) with diisocyanates such as hexamethylene diisocyanate (4a), 4,4′‐methylenedicyclohexyl isocyanate (4b), 1,3‐cyclohexylenedimethyl isocyanate (4c), 2,4‐toluylene diisocyanate (4d) and 4,4′‐methylenediphenyl isocyanate (4e), and their thermal properties were investigated. The resulting polymers show a liquid crystalline state at 206–230, 160–216, 186–226 and 144–204°C, respectively, and the polymer obtained from4ehas a melting point at 272°C, determined by DS

ISSN:0025-116X    

DOI:10.1002/macp.1986.021871005

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractN‐carboxyanhydride of γ‐benzylL‐glutamate (N‐CA‐γ‐BG) was polymerized with the lowmolecular‐weight initiators 2,2′‐dithiodiglycinanilide (1) and 2,2′‐azo‐2,2′‐dimethyldipropionohydrazide (2) and with poly(methyl methacrylate) (PMMA) of different molecular weights containing amino and hydrazide end groups, exhibiting different nucleophilicities. For comparison, the N‐CA was also polymerized with initiators described in the literature. It could be shown that the induction period depends on the nucleophilicity of the end groups of the initiator. In contrast to the low‐molecular‐weight initiators, the polymerization of the N‐CA wi

ISSN:0025-116X    

DOI:10.1002/macp.1986.021871006

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractIn presence of traces of strong acids 2,2,6,6‐tetramethylpiperidine‐N‐oxyl (2) induces the decomposition of hydroperoxides such astert‐butyl hydroperoxide (1) and cumene hydroperoxide (CHP).2disproportionates in presence of hydrogen chloride into 1‐hydroxy‐2,2,6,6‐tetramethylpiperidine (5) and 2,2,6,6‐tetramethyl‐1‐oxopiperidinium chloride (4). This oxammonium salt is the active component which catalyses the decomposition of the hydroperoxide1by forming alkylperoxy radicals and the hydroxylamine derivative5. The peroxy radicals are converted into alkyloxy radicals and molecular oxygen, and the oxyradicals regenerate2and an alcohol. The concentration of2remains constant through the whole period of the reaction. If1is present in an excess over2and the oxammonium salt4, additional protons are needed to decompose

ISSN:0025-116X    

DOI:10.1002/macp.1986.021871007

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractPoly(oxyethylene)s with dithioster end groups were obtained from mono‐ and dihydroxyl terminated commercial polymers by reaction with dimethyl chloroacetamide, subsequent thionation of the amide group, and usual conversion of the thioamides into the dithioesters14, 15and20, 21. The best results were obtained in the syntheses of theS‐carboxymethyl dithioesters (15and21). The resulting reactive poly(oxyethylene)s were grafted upon silica tubes and electrophoresis cells, previously activated by aminopropylsilanization. These graftings result in lowering of the surface potential of the tubes and in suppression of the electro‐osmosis flow in an electrophoresis cell tested with a TiO2standard s

ISSN:0025-116X    

DOI:10.1002/macp.1986.021871008

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractBlends of poly(tetramethylene terephthalate) [poly(butylene terephthalate) (PBT)] with a liquid crystalline polyester, poly(decamethylene 4,4′‐terephthaloyldioxydibenzoate) (HTH 10), obtained by solution precipitation, were characterized by optical microscopy, X‐ray diffraction and differential calorimetry. The morphology and phase behaviour of the blends are sensibly influenced by the composition. X‐ray data support the existence of separated crystal phase of the two polymers only for HTH10 contents higher than 30 wt.‐%. An increase of the clearing temperature of the original blends is found with decreasing concentration of the mesomorphic polymer in the range 100 to 30 wt.‐%. On cooling from the isotropic melt, a single crystallization process is observed, whose temperature decreases with increasing amount of HTH10. A large depression of the melting temperature of PBT is found in the composition range 0 to 50 wt.‐% of HTH10. Blends quenched from the isotropic state exhibit one single glass transition temperature, intermediate between those of the starting polymers. The results suggest the occurrence of miscibility phenomena of PBT and HTH10 in the amo

ISSN:0025-116X    

DOI:10.1002/macp.1986.021871009

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractComplexes of Rh(I) with 4‐vinylpyridine and poly(4‐vinylpyridine) were isolated and studied by infrared and electronic spectra and elemental analysis. The electrochemical behaviour of a platinum electrode coated with metal‐polymer complex was studied by consecutive potential sweeps. The complex was oxidized at potentials higher than 600 mV (S.C.E.) in 0,5 M H2SO4and reduced at lower potentials. Consecutive sweeps produce a reticulation of the complex and therefore lead to electrode stabilization. The influence of the anodic and cathodic limits of the potential sweeps and of the metal to polymer ratio was also studied. The cathodic photoresponse of this electrode and its conductivity in a Fe2+/Fe3+solution is also rep

ISSN:0025-116X    

DOI:10.1002/macp.1986.021871010

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY