摘要:

Abstract[1.1.1]Propellanes are introduced to polymer chemistry as a new class of highly reactive monomers which polymerize regiospecifically with breaking of the central CC σ‐bond. These rather unique hydrocarbon monomers undergo ring‐opening polymerizations with formation of both homo‐ and copolymers and, in addition, can be used as starting materials for classical poly‐condensation chemistry. A wide variety of new polymers is presented all of which contain the bicyclo[1.1.1]pentane fragment, a linearly connecting, rigid unit. This article focusses on questions related to synthesis and structure elu

ISSN:0025-116X    

DOI:10.1002/macp.1991.021921101

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractPolystyrene (PS)‐polydimethylsiloxane (PDMS) triblock copolymers with well‐defined block lengths and silanol reactive end‐groups were synthesized by anionic polymerization as prepolymers for condensation reactions. Multiblock PS‐PDMS copolymers characterized by molecular and chemical homogeneity could be obtained either by self condensation of the silanol groups of by reaction with dichlorodimethylsilane. The kinetic constants, the activation energy, the extent of reaction and the molecular characteristics of the multiblock copolymers were determined as a function of the molecular weight of the prepolymer, the water content of the reaction medium and the concentration of HCl acting as catalyst in the dehydration reaction. The kinetic constants and the ultimate extent of the reaction could be correlated to the molecular weight of the prepolymer and to the viscosity of the reaction medium. DSC measurements of the multiblock copolymers show clearly the presence of two‐phase materials with mechanical properties depending on the PDM

ISSN:0025-116X    

DOI:10.1002/macp.1991.021921102

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe projection operator method of matrix algebra is applied to calculate the unperturbed dimensions of an independently hindered rotating bond model for linear chain molecules. It does not require eigenvectors of a given transformation matrix in order to evaluate products of that matrix. This is an advantage to usual matrix diagonalization methods. As a result, we obtained four different types of conformations depending upon the values of parameters adopted. One of them shows a typical dependence on the number of bondsN, which has also been given by the usual matrix diagonalization method. Two further conformations are rather extended compared with the first one. In addition, as the fourth one we obtained also a helix‐like conformation. These conformation types correspond to those previously obtained by continuous models for stiff‐chain polym

ISSN:0025-116X    

DOI:10.1002/macp.1991.021921103

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe influence of the spacer length was investigated for the correlation between the network anisotropy and the order parameter of the mesogenic units. Stress‐optical measurements show that a closer coupling of the mesogenic moieties to the polymer backbone results in an increased interaction between the mechanical field and the mesogenic groups. The correlation between the phase transformation temperatureTNIand the mechanical stress σ is represented using both, our experimental measurements and the derivation from the Landau‐de Gennes (LDG) formulation. From our results, it is possible, for the first time, to estimate the cross‐coupling coefficientUbetween the order parameter and the strain of a nematic elastomer. The analysis of the elastic properties of the elastomers suggests that non‐linear coefficients might become important to obtain quantitative agreement between theory and ex

ISSN:0025-116X    

DOI:10.1002/macp.1991.021921104

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe deposition of films from an argon plasma containing a mixture of ethylene oxide or hydrogen and perfluorohexane was tried to obtain very hydrophobic, less hydrophobic and intermediate coatings. This paper studies more extensively the deposition of a thin coating from a perfluorohexane and hydrogen plasma on polysulfone and polyhydroxybutyrate membranes to optimize their surface properties without affecting their filtering properties. The plasma deposition of smooth and very hydrophobic fluorocarbon coatings seems to increase the bio‐ and hemocompatibility of poorly biocompatible membranes. The treated substrates were characterized by measuring the mass variations, surface profilometry and contact angle measurements, as well as scanning electron microscopy and electron spectroscopy for chemical analysi

ISSN:0025-116X    

DOI:10.1002/macp.1991.021921105

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractEthylene copolymers with propene and/or 1,3‐butadiene were obtained using bis(η5‐cyclopentadienyl)zirconium dichloride (1) or ethylenebis[1‐3a, 7a‐η‐(4,5,6,7‐tetrahydro)‐1‐indenyl]zirconium dichloride (2) and methylalumoxane as catalytic systems. A detailed13C NMR analysis of the copolymers was performed. The resonances in the olefinic region of the terpolymers were assigned to ethylene/butadiene/ethylene and propene/butadiene/ethylene sequences while the butadiene/propene sequence was ruled out. Analogously, no polymers were obtained from the polymerization of propene in the presence of 1,3‐butadiene. It is thus shown that the conjugated diene is an inhibitor for the polymerization of α‐olefins. The presence oftrans‐1,2‐cyclopentane rings was detected both in the ethylene/butadiene copolymers and in the ethylene/propene/butadiene terpolymers. A different behaviour of the

ISSN:0025-116X    

DOI:10.1002/macp.1991.021921106

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe synthesis of dextran radiocontrast carriers was undertaken to obtain derivatives expected to have slow and controlled biodegradation as well as slow extravascular diffusion features. The results presented here particularly concern derivatives including a methylamide spacer, prepared by condensation of the amine function of the contrast product with carboxymethylated dextran (CMD). The effect of various coupling reagents on the final yields is disucssed. Concerning the macromolecular features, all the synthesized products were characterized by acid‐base titration, elemental analysis, flame photometry, spectroscopic determinations and gel‐permeation chromatography. GPC showed that the carboxymethylation of dextran leads to some reticulation (doubling the molecular weights), whereas the coupling of CMD with the contrast compound does not alter the molecular weight and the polydispersity index of the products apprecia

ISSN:0025-116X    

DOI:10.1002/macp.1991.021921107

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractPhase diagrams of amorphous polymer blends are discussed that are recorded using cast films. Films of all blend compositions were cast at temperatures ranging over a wide interval, using different solvents, both above and below the glass transition temperatures of the blends. Phase diagrams thereby obtained can, if there is a proper choice of solvents and conditions, show the miscibility of polymers not only in the liquid but also in the glassy state. The theory of blend film casting is analyzed using the classical Flory‐Huggins model for compatibility and the Fox‐equation for the glass transition. It turns out that miscibility is reliably determined when slightly selective solvents are used. Errors made with non‐selective and too selective solvents are estimated. The film‐casting method was tested with blends of poly(methyl methacrylate) and random copolymers of styrene and methyl metha

ISSN:0025-116X    

DOI:10.1002/macp.1991.021921108

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe synthesis of new poly[(vinyl 4′‐alkoxyazobenzene‐4‐carboxylate)‐co‐(vinyl alcohol)]s4a–cby Einhorn esterification of poly(vinyl alcohol) with 4′‐alkoxyazobenzene‐4‐carbonyl chlorides3a–cprepared in two steps from 4′‐hydroxyazobenzene‐4‐carboxylic acid (1) is described. The degree of esterification is found to be about 85 mol‐%. Infrared,1H and13C nuclear magnetic resonance and ultraviolet spectroscopical data of the

ISSN:0025-116X    

DOI:10.1002/macp.1991.021921109

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractDepending on the kind of initiator, anionic polymerization of 4‐(α,α‐dimethylbenzyl)phenyl methacrylate in toluene at −78°C led either to highly isotactic or predominantly syndiotactic polymers as determined by13C NMR spectroscopy. The glass transition temperature difference between the syndiotactic and isotactic polymer appeared to be smaller than in case of poly(alkyl methacrylates), probably because of a larger stiffening effect by the bulky aromatic ester group on the isotactic backbone than on the syndiota

ISSN:0025-116X    

DOI:10.1002/macp.1991.021921110

出版商:Hüthig&Wepf Verlag    

年代:1991

数据来源: WILEY