摘要:

AbstractAzobenzene moiety‐containing methylcellulose (AB‐MC) was prepared, the changes of the cloud point of its aqueous solutions as a thermotropic sol‐gel transformation behaviour were investigated under irradiation with UV light. AB‐MC's with degrees of substitution by the azobenzene moiety DSAB>2,5 · 10‐2were insoluble in water. The azobenzene moiety in the AB‐MC was confirmed to be reversibly isomerized from thetrans‐ to thecis‐form under irradiation with UV light of wavelengths 390>λ>310 nm and from thecis‐to thetrans‐form under irradiation with visible light of λ>400 nm. The cloud point value of the aqueous solution of AB‐MC increased under irradiation with UV light of 390>λ>310 nm for the AB‐MC's with a DSABvalue in a certain range and the extent of the increase in the cloud point value was higher at hig

ISSN:1022-1336    

DOI:10.1002/marc.1995.030161201

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractSynthesis and cationic ring‐opening polymerization of new 1,6‐anhydro‐β‐lactose derivatives such as hexa‐O‐methylated (LSHME),tert‐butyldimethylsilylated (LSHSE), and benzylated 1,6‐anhydro‐β‐lactoses (LSHBE) were first investigated. The disaccharide monomers were prepared by methylation,tert‐butyldimethylsilylation, and benzylation of 1,6‐anhydro‐β‐lactose, respectively. It was found that LSHME was readily polymerized with such Lewis acid catalysts as PF5and SbCl5to give stereoregular 2,3‐di‐O‐methyl‐4‐O‐(2′,3′,4′,6′‐tetra‐O‐methyl‐β‐D‐galactopyranosyl)‐(1→6)‐β‐D‐glucopyranans which are comb‐shaped polysaccharide derivatives. However, LSHSE and LSHBE had almost no polymerizability. It was revealed that the ring‐opening polymerizability of the anhydrodisaccharide monomers was influenced by the steric hindrance of the hydroxyl‐protective groups. Ring‐opening copolymerization of LSHME with 1,6‐anhydro‐2,3,4‐tri‐O‐benzyl‐β‐D‐glucopyranose (LGTBE) in various ratios of monomer feeds was also examined to afford the corresponding copolymers. Structural analyses of the monomer

ISSN:1022-1336    

DOI:10.1002/marc.1995.030161202

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

Abstract4‐Methyl‐1,3‐pentadiene was polymerized with the MAO/CpTiCl3(MAO: methyl‐aluminoxane, Cp: Cyclopentadienyl) system to yield a highly stereoregular syndiotactic 1,2‐polymer. Fiber diffraction patterns indicate two crystalline modifications: a major one with a repeat of 11.73 Å and minor amounts of a zig‐zag planar polymorph (axial repeat 5.05 Å). Energy calculations account for three nearly isoenergetic conformations: the more stable one, with repeat of 11.65Å, is (T6G2T2G2) analogous to the one recently reported for syndiotactic poly(propylene) (Chatani

ISSN:1022-1336    

DOI:10.1002/marc.1995.030161203

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe complex dielectric permittivity has been measured in the 103−106Hz frequency range for selected random copolyesters of poly(ethylene terephthalate). The variation of the dielectric properties with temperature has been qualitatively related mainly to two processes. The α relaxation, which is associated with the glass transition, has been shown to be dependent on the molecular order of the systems. The β relaxation process has been assigned to local motions of the ester groups attached to both sides of the aromatic rings. The β process is also shown to exhibit a dependence on molecular o

ISSN:1022-1336    

DOI:10.1002/marc.1995.030161204

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThree kinds of zirconocene catalysts, supported on polysiloxanes substituted with methylindenyl, methyl‐fluorenyl and two indenyl groups, respectively, were prepared and applied to propene and ethylene polymerizations using methylaluminoxane as cocatalyst. Both the activity and stereospecificity of these catalysts were found to lie between those of corresponding homogeneous and SiO2‐supported catalysts. Surprisingly, all the catalysts gave a mixture of atactic and isotactic poly(propylene), plausible reasons for which are briefly discus

ISSN:1022-1336    

DOI:10.1002/marc.1995.030161205

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe coil‐globule transition of poly(N‐isopropylacrylamide) (systematic name: poly‐[1‐(isopropylaminocarbonyl)ethylene]) has been viscometrically investigated in low‐concentration aqueous sodium dodecyl sulfate solution. In this environment, even if the macromolecular coils collapse as the temperature increases above the lower critical solution temperature of the polymer, 34°C, the polymer does not precipitate. It seems that the hydrophobically collapsed macromolecular coils do not aggregate, but remain in solution with the aid of surface charges supplied by surfactant ions adsorbed through hydrophobic in

ISSN:1022-1336    

DOI:10.1002/marc.1995.030161206

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe orientation of the microdomains at the free surface of solvent‐cast films of a polystyrene‐block‐polybutadiene‐block‐polystyrene triblock copolymer with cyclindrical morphology was studied by coupling transmission electron and scanning force microscopies (SFM‐TEM). It was found that the cylinders of polystyrene, which are assembled in grains randomly oriented in the bulk, tend to reorient with the main axis perpendicular to the surface. SFM investigation indicates that the hexagonal symmetry of the cylinders is also maintained at the free surface which is characterized by protrusions and corrugation with size and characteristic distances closely related to the cylindrical morphology visible in the bulk. Good quantitative agreement between TEM and SFM measurements

ISSN:1022-1336    

DOI:10.1002/marc.1995.030161207

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractA new oxygen/nitrogen separation membrane based on an ionomer of sulfonated EPDM (ethylene‐propene‐diene terpolymer) containing Co2+ions was synthesized and investigated. It was found that the oxygen permeability coefficient and the separation factor for O2/N2of the ionomer membrane are simultaneously enhanced at lower gas pressure difference. This result is believed to be caused by a polymer coordinate complex formed in the ionomer. ESR spectra provided an evidence of the cobalt‐oxygen a

ISSN:1022-1336    

DOI:10.1002/marc.1995.030161208

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe anionic ring‐opening polymerization of L‐lactide was initiated by dipotassium‐poly‐isobutylene‐alcoholate telechelic polymer to yield poly(L‐lactide)‐block‐polyisobutylene‐block‐poly(L‐lactide) triblock copolymer, a partially biodegradable thermoplastic elastomer. The pure triblock copolymer was obtained by gradient column chromatography on silica gel. The molar mass and molar mass distribution of the block copolymer was ascertained by SEC and quantitative1H NMR spectroscopy. It showed two glass transitions and

ISSN:1022-1336    

DOI:10.1002/marc.1995.030161209

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this work the relationship between structure and water sorption for epoxy films was studied using electrochemical impedance spectroscopy. It is shown that the electrochemical impedance spectroscopy can be applied to obtain information about the amount of water absorbed by the epoxy film and the water permeation through the film, while only the amount of water absorbed is obtained from the “sorption method”. The free volume is the decisive factor for both the amount of water in the cured epoxy film and water permeation through the f

ISSN:1022-1336    

DOI:10.1002/marc.1995.030161210

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY