摘要:

AbstractThis article describes recent achievements in the field of micellar polymers, or “polysoaps”. Taking advantage of zwitterionic model polymers, systematic variations of the molecular architecture have provided an improved understanding of the relationship between the molecular structure of the polymers and their key properties such as surface activity and solubilization capacity. Useful rules are established, which take into account much of the previous data in the literat

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940101

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe dehalogenative polycondensation of 3,6‐dibromo‐N‐ethylcarbazole was catalyzed by a Ni(0)‐based complex, generated inN,N‐dimethylacetamide by electroreduction of NiBr2/2,2′‐bipyridine. The process involves three different successive reaction steps: electrolysis of Ni(II) to Ni(0); insertion of the latter into a CBr bond of monomer leading to CNiBr*active species; dehalogenative coupling between active sites and monomer, yielding oligomers. From kinetics of electrogeneration of the catalytic system in the absence of monomer, a first‐order reaction was determined. Insertion and coupling reactions were found to be second order, and comparison of the values of the corresponding rate constants clearly showed that couplings is the rate‐determin

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940102

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractCationic polymerizations of various 5‐alkyl‐2‐norbornenes (RNB, where RH, CH3, C2H5, C5H11, C7H15, and C10H21) were carried out by the AlEtCl2/tert‐butyl chloride catalyst system, and the effect of the length of the alkyl substituents on the monomer reactivity and polymerizability, polymer structure, and softening point (SP) were investigated. The introduction of an alkyl substituent into 5‐position of the norbornene ring remarkably reduces the monomer reactivity and polymerizability, although the length of alkyl group does not affect them.13C NMR structural analysis of poly(RNB)'s revealed that not only the normal 5‐or 6‐alkyl‐2,3‐unit but also other structures such as 5‐ or 6‐alkyl‐2,7‐, 4‐alkyl‐3,6‐units, etc., are the most plausible structures for the repeating units. Furthermore, the existence of the 4‐alkyl‐3,6‐repeating unit and of the alkylidene type end‐group indicates the presence of an intermediate tertiary cation (5‐alkyl‐5‐norbornyl cation), which causes the low reactivity and polymerizability of the monomers. The SP of oligomers of equal molecular weight (DPn= 3–5) decreases in the following order: HNB, CH3NB,C2H5NB>C5H11NB>C7H15NB>C10H21NB. The effect the alkyl substituent length on the SP is discussed on the basis of the13C spin

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940103

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe synthesis of high‐molecular‐weight polyesters based on 1,4:3,6‐dianhydro‐D‐sorbitol (DAS), 1,4:3,6‐dianhydro‐D‐mannitol (DAM) and 1,4:3,6‐dianhydro‐L‐iditol (DAI) is reported. The polymers were obtained by polycondensation in solution of the dianhydrohexitols with terephthaloyl dichloride and 2,5‐diethoxyterephthaloyl dichloride. The side groups of the latter monomer lead to a marked improvement of the solubility of the resulting polyesters which can be characterized by NMR techniques and osmometry. It is shown that all polyesters exhibit an excellent stability against thermal decomposition. Materials deriving from the polycondensation with terephthalic acid have glass transitions above 200°C if the molecular weight is high enough. The wide‐angle X‐ray analysis shows that polyesters deriving from terephthalic acid and DAM as well as DAI are semicrystalline. All results demonstrate that these polyesters partly deriving from renewable carbon sources present promising highTgmaterials with

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940104

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe reactivity of the amino groups of partiallyN‐acetylated chitosans (PAC‐H) was investigated using cyanuryl dichloride, pyrocarbonates, activated ester, carbodiimide and epoxy‐activated polymethacrylamide beads. The maximal reactivity was attained at neutral pH in the cases of the reaction with a monomethoxypoly(ethylene glycol) succinimidyl succinate, and with isonicotinic acid mediated by a water‐soluble carbodiimide. On the contrary, the maximal reactivity was attained under weakly basic conditions in the cases of reactions with diethyl pyrocarbonate, dimethyl pyrocarbonate and cyanuryl dichloride. The highest amount of PAC‐H was immobilized on the surfaces of epoxy‐activated polymethacrylamide beads at weakly alkaline pH. From these results it was concluded that PAC‐H's are favorable for preparing randomly substituted derivatives and for immobilizing them on surfaces because their solutions are stable at neutral and alkaline pH in contrast to conventional chitosans. The structure of the products was analyzed by IR spectroscopy, and a method for estimating the degree of substitution by I

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940105

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe temperature‐concentration diagram for the system atactic polystyrene/trans‐decalinSystem. name:trans‐decahydronaphthalene.was studied by optical observations and calorimetric investigations. A liquid‐liquid demixing interferes with the glass transition of the polymer‐solvent system. It results in the solidification of the solution. The binodal, the spinodal and the position of the critical point were investigated for a sample with narrow molecular weight distribution. The formation of different morphologies, based on different cooling processes, is il

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940106

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractLow‐molecular‐weight organosilane polymers were prepared by sodium coupling of dichloro‐methylphenylsilane (1) with chlorotrimethylsilane (2). Gel permeation chromatography (GPC), IR and NMR (1H,13C and29Si) analysis of the crude product (3) were performed and compared with those of the isolated first oligomers, trisilane (3a) and tetrasilane (3b). The GPC characteristics, especially high resolution ones, in accordance with the α,ω‐bis(trimethylsilyl)‐oligo(methylphenylsilane) structure are compared with those of hydrocarbon polymers. The relations of the NMR characteristics of the methylphenylsilanediyl unit with the position along the chain and the configuration of the diads are approached. Some spectroscopic indications of the secondary structure ar

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940107

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractPolyisocyanates (nylon 1) with azochromophores in the side chains were prepared for the first time. For this purpose we have synthesized two new azo dyes containing isocyanato groups. The monomers were copolymerized with alkyl isocyanates to prepare chiral dye‐containing polyisocyanates. Optical rotatory dispersion and circular dichroism measurements support the helical polymer structure with predominantly one twist sense (due to the chiral side chains, P and M helices are diastereomeric). The completely reversible photochemical isomerization (transtocis) of the azochromophores reaches high conversions (about 80%), but does not change the conformation of the main chai

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940108

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractA new disaccharide monomer, 6(‐methacryloxyloxy)hexyl β‐D‐cellobioside (CHMA,7h), was prepared through a five‐step procedure (starting from cellobiose), in which the glycosylation and esterification reactions have been optimized. Kinetics of radical homopolymerization in dimethyl sulfoxide solution were studied through1H NMR, allowing the determination of the parameterkp/kt1/2. Copolymerizations with styrene (S) were also investigated, giving the reactivity ratiosrS= 0,64 andrM= 0,08. Characterization of the various (co)polymers in terms of composition, microstructure and molecular weight was carried out using1H and13C NMR spectroscopy and gel‐permeation chromatography in tetrahydrofuran, respectively. A preferential syndiotactic configuration was clearly evidenced in the h

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940109

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractPhoto and thermal polyrecombinations of some captodative substituted cyano‐, methoxycar‐bonyl‐, and phenylmethane derivatives were carried out using peroxides as oxidizing agents at room temperature and 130°C. Cyano‐substituted methane derivatives easily gave a polymer with a molecular weight of several thousands by both photo and thermal polyrecombinations. Especially, phenylacetonitrile afforded a polymer in good yield even under conditions at which diphenylmethane gave no polymer. Methyl methoxyacetate gave no polymer in the thermal reaction, but afforded a polymer when using high concentrations of an oxidizing agent in the photoreaction.1H nuclear magnetic resonance and electron paramagnetic resonance spectra demonstrated the production of a polymer with a structure mainly consisting of 1,1‐disubstituted methylene units and the generation of a captodative substituted methyl radical in the react

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940110

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY