摘要:

AbstractA new route to poly(ferrocenylsilanes) under mild conditions via the ring‐opening polymerization of silicon‐bridged [1]ferrocenophanes is presented. Catalytic amounts of the transition metal complexes [Rh(cyclooctene)2(μ‐Cl)]2, Pd(1,5‐cyclooctadiene)Cl2, PdCl2and PtCl2in C6D6at room temperature afforded high molecular weight poly(ferrocenylsilanes) (2). In some cases a symmetrical dimer (3) was obtained as a b

ISSN:1022-1336    

DOI:10.1002/marc.1995.030160901

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractA series oftert‐butyl substituted zirconocene/methylaluminoxane catalysts illustrates the potential for the tailoring of olefin oligomers with extremely narrow molar mass distributions, which are explained on the basis of a chain‐length dependent propagation rate. Comparative oligomerization experiments provide a means to estimate the relative rates for chain propagation versus chain transfer as well as a correlation with the metallocene struct

ISSN:1022-1336    

DOI:10.1002/marc.1995.030160902

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe chain transfer reaction by hydrogen in the initial stage of propene polymerization with MgCl2‐supported Ziegler catalyst was studied by means of the stopped‐flow polymerization. The yield and molecular weight of polypropene produced in the initial stage were not affected by hydrogen. Thus, the method was successfully applied to find the region in which hydrogen does not act as a chain transfer reagent. On the other hand, a chain transfer reaction proceeded in the initial stage of polymerization by using Zn(C2H5)2. Furthermore, when the catalyst was treated with Al(C2H5)3before polymerization, the molecular weight of the produced polymer was decreased by using hydrogen, indicating that it acted as a chain transfer agent for the catalyst modified by pre‐trea

ISSN:1022-1336    

DOI:10.1002/marc.1995.030160903

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe crosslinking of ferroelectric liquid‐crystalline (LC) polysiloxanes — performed within the region of microphase separation — allows the preparation of LC‐elastomers which combine macroscopic form stability (insolubility) with nearly unchanged switching time (compared to the uncrosslinked po

ISSN:1022-1336    

DOI:10.1002/marc.1995.030160904

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractBiodegradable hydrogels composed of oligopeptide‐terminated poly(ethylene glycol) (PEG) and dextran with interpenetrating polymer network (IPN) structure were proposed as a novel substrate for multistimuli‐responsive drug delivery. IPN‐structured hydrogels were synthesized by sequential crosslinking reactions ofN‐methacryloyl‐glycilglycilglycil‐terminated PEG and dextran.In vitrodegradation of the IPN‐structured hydrogels was examined using papain and dextranase as model enzymes for hydrolyzing the oligopeptide and the dextran. Specific degradation in the presence of papain and dextranase was observed in the IPN‐structured hydrogel with a particular composition of PEG and dextran, whereas this hydrogel was not degraded by one of

ISSN:1022-1336    

DOI:10.1002/marc.1995.030160905

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

Abstract7‐Methyl‐2‐methylene‐ (1) and 7‐methyl‐2,3‐dimethylene‐1,4,6,9‐tetraoxaspiro[4.4]nonane(2)were synthesized and characterized by elemental analysis, IR,1H NMR and13C NMR spectroscopy. Radical polymerization of the spiro orthocarbonates (SOC)1and2show that they undergo primarily vinyl polymerization with a low degree of ring‐opening reaction. Homopolymerization of2at 120°C with di‐tert‐butyl peroxide gives a transparent crosslinked polymer and the polymerization generates a 1

ISSN:1022-1336    

DOI:10.1002/marc.1995.030160906

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe polarographic behaviour of hydrolyzed propene‐maleic anhydride copolymers in the interval pH 2.0–11.0 has been investigated by differential pulse polarography in aqueous lithium chloride solution at 25°C. In dependence on the pH‐value, one, two or three signals, belonging to the acid groups in the copolymer, appear in the polarograms. Three apparent polarographic acid constants have been determined graphically from the changes in the half‐wave potential of the separate peaks in correlation

ISSN:1022-1336    

DOI:10.1002/marc.1995.030160907

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe strain‐induced director reorientation process in nematic liquid single crystal elastomers is investigated for the case of an arbitrary angle between the original director and the external stress axis. If the mechanical stress is applied perpendicular to the original director axis, the reorientation process sets in at a threshold strain. The mesogens are realigning ‘clockwise’ or ‘counter‐clockwise’ towards the axis of external stress, simultaniously the monodomain structure is distorted and a periodic pattern formation is observed. If the mechanical stress is applied obliquely with respect to the original director axis, a uniform director reorientation is obtained with retention of the monodomain structure. No threshold strain is observed for this process. The existence of a threshold strain in the case of a perpendicular arrangement of the director to the external stress axis can be understood as a consequence of the distortion of the monodomai

ISSN:1022-1336    

DOI:10.1002/marc.1995.030160908

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractAn attempt was made to prepare periodic polymers having promesogenic units of various lengths. Due to a certain distribution within these units, copolymers of this structure should rather be called pseudoperiodic. In order to understand better the behaviour of such systems, copolymerization of tetrahydrofuran (THF — soft units) with 7‐oxabicyclo[2.2.1]‐heptane (BC — hard units) was studied. The kinetically and thermodynamically controllable copolymerizations were elaborated, leading to products of different distribution of the THF and BC units. The apparent reactivity ratios are dependent on the copolymerization conditions due to the reversibility of the propagations on the THF type of active species. They vary: r̄1from 0.09 to 2.72, r̄2from 0.31 to 1.57 (1 stands for BC, 2 for THF). Pseudoperiodic copolymers of the structure\documentclass{article}\pagestyle{empty}\begin{document}$\rlap{-} [\rlap{–} ({\rm BC}\rlap{-} )_x {\rm THF}\rlap{-} ]_n $\end{document}, where x̄ = 1 to 4, were prepared carrying out the copolymerization above the ceiling temperat

ISSN:1022-1336    

DOI:10.1002/marc.1995.030160909

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe one‐step synthesis of 2,6‐naphthalenedicarboxylic acid from naphthalene with carbon tetrachloride, copper powder and aqueous alkali has been achieved under mild conditions by the use of β‐cyclodextrin as catalyst, producing 2,6‐naphthalenedicarboxylic acid in 65 mol‐% yield with 79% s

ISSN:1022-1336    

DOI:10.1002/marc.1995.030160910

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY