摘要:

AbstractA new polyamidation reaction betweenN,N′‐bistrimethylsilylated diamines and 2,2′‐p‐phenylenebisazalactones inN,N‐dimethylacetamide was investigated. By the interaction of bisazalactones withNα,Nε‐bistrimethylsilylated L‐lysin alkyl ester, polyamides were obtained containing dipeptide links in the main chain. It was shown that these can be transformed into water‐soluble polyacids upon saponification o

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940111

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractAs a part of our interest in the performance of [Ti2(OC2H5)8Cl]2Mg2(μ‐Cl)2as Ziegler‐Natta catalyst, the polymerization of styrene with a toluene solution of this compound and methyl‐aluminoxane as cocatalyst was performed. It was found that the present catalytic system promotes the syndiospecific polymerization of styrene with high stereoregularity and the results were compared with those obtained with MgCl2‐supported or unsupported Ti(OC2H5)4catalysts. Determination of the titanium oxidation states and electron spin resonance (ESR) measurements both in the absence and in the presence of styrene were carried out for all the catalytic systems aimed at shedding some light on the nature of the active

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940112

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractA kinetical investigation on the consumption of a chain transfer agent in the free‐radical polymerization of vinyl acetate (VAc) was carried out. A new method to control the degree of polymerization of poly(vinyl acetate) (PVAc) or poly(vinyl alcohol) (PVA) as well as the end group content by continuous addition of a chain transfer agent, whose chain transfer constant is much larger than unity such as thiol compounds, during the course of VAc polymerization was proposed. The method using 2‐mercaptoethanol was applied to the preparation of lowmolecular‐weight PVAc and PVA withM̄w/

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940113

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractPoly(vinyl alcohol) (PVA) and poly(vinyl acetate) having a thiol group at one end were synthesized by free‐radical polymerization of vinyl acetate in presence of thioacetic acid as a chain transfer agent followed by treating with sodium hydroxide/methanol and ammonia, respectively. It was found that block copolymers containing the PVA sequence as one constituent were obtained by the redox‐initiated polymerization of some vinyl monomers, for example, acrylic acid (AA) and acrylamide (AAm), using PVA having a thiol end group as reductant and an oxidant such as potassium bromate and potassium persulf

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940114

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

Abstract1,2‐Butadiene (BD‐1,2) was shown to be a chain terminating/transferring agent in the butyllithium (nBuLi)‐initiated polymerization of 1,3‐butadiene in hexane solvent by Adams et al. Based on model reactions and circumstantial evidence they proposed that BD‐1,2 terminates the polymerization by extracting Li from the living chain end. The lithiated BD‐1,2 formed may initiate new chains causing chain transfer or isomerize to lithiated ethylacetylene (system. name: 1‐butyne), a nonactive species. This paper proposes a modification of the mechanism suggested by Adams et al. Kinetic investigations of the model reaction between nBuLi and BD‐1,2 by infrared spectroscopy have shown that the first, and rate‐determining, step is the isomerization of BD‐1,2 to ethylacetylene, followed by lithiation. It is proposed that the lithiated ethylacetylene can initiate new chains, thereby cau

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940115

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThermotropic liquid‐crystalline polymers (2a–2e, 3a–3c) linked via the bis(ß‐diketonato)‐copper(II) complex were prepared by mixing the bifunctional bidentate ligand (1a–1c) with copper(II) chloride. The homopolymers2c–2eand the copolymers2a–3cwere ascertained to exhibit a stable mesophase by means of polarizing microscopic observation. The homopolymers show at least a smectic mesophase and the copolymer exhibit both smectic and nematic ones. Fibers were prepared by melt‐drawing of the molten polymers at the mesophase temperature into air at room temperature except for2aand2b. Electron spin resonance (ESR) spectra of the melt drawn fibers indicated that the plane of the square planar bis(ß‐diketonato)copper(II) complex in the fiber is oriented parallel to the fiber axis. X‐ray diffraction patterns from the melt‐drawn fibers are characterized by several sharp inner reflections at meridional position and a diffuse one at equatorial position, suggesting that the fibers possess an axial orientation with smectic A phase which is frozen in d

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940116

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThis paper describes the roles of silica (SiO2), the butoxy ligand (OBu) and ethyl benzoate (EB) on ethylene/1‐butene copolymerization with MgCl2/SiO2‐supported titanium catalysts. The distribution of SiO2and of the elements Mg and Ti was observed by means of an energy‐dispersed X‐ray micronalyzer on a scanning electron microscope (SEM). An inversed Si/Mg ratio results, at invariant Ti/Mg ratio andOBu content, in higher catalyst efficiency and higher comonomer incorporation, with a correspondingly decreased crystallinity of the copolymers. Thus, the inert carrier SiO2favors copolymerizability, as seen from the values of the reactivity ratios. The copolymer compositional distribution is also affected by the SiO2content, as seen from the DSC curves of the copolymers. As to the copolymer morphology, addition of SiO2makes the copolymer particles larger and m

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940117

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe stability of the helical conformation in optically active poly(triphenylmethyl methacrylate) (PTrMA) was investigated by heating the polymer solutions at 100°C. The optical rotation slowly disappeared with time, and some preliminary experiments showed that this phenomenon is not due to a typical racemization process, as it is accompanied by a loss of triphenylmethyl (Tr) groups due to secondary reaction. Experimental results in the presence of methanol indicated that the decrease of optical activity occurs according to first‐order kinetics and qualitatively methyl triphenylmethyl ether was isolated from the final solution. In order to explain the above results, full characterization of copolymers obtained by interrupting the methanolysis at different conversions was performed. As a working hypothesis, it was assumed that the reaction starts at the end of the helices with a Tr‐oxygen bond fission and the reaction proceeds along the chain mainly with formation of block copolymers consisting of one block of PTrMA and one block of a probably random methacrylic acid anhydride/methacrylic acid copol

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940118

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe study of the charge transfer (CT) complexation in mixtures containing carbazolyl electron donor (D) and dinitrobenzoyl electron‐acceptor (A) moieties show stronger association effects in mixtures of polysiloxanes than in mixtures of low‐molecular‐weight model compounds. The increasing CT‐association in polymer systems is explained by a “macromolecular cage effect”. Cooperativity effects are believed to cause a “zip‐like” matching of the complementary polymeric backbones. UV‐spectroscopy and viscometric data indicate the formation of both bimolecular D : A and trimolecu

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940119

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe synthesis and characterization of new poly({6‐[4‐(4‐cyanophenylcarbamoyl)phenoxy]hexyl methacrylate}‐co‐{6‐[4‐(4‐ cyanophenylazo)phenoxy]hexyl methacrylate}) are reported. Their liquid‐crystalline properties are investigated using differential scanning calorimetry, polarizing microscopy and X‐ray diffraction techniques. The glass transition temperatures and the clearing points can be influenced by variation of the copolymer composition. The substances offer a relatively broad temperature range of mesomorphic properties suitable for ph

ISSN:0025-116X    

DOI:10.1002/macp.1993.021940120

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY