摘要:

AbstractCopolymerization of styrene (St) and isoprene (IP) with nickel(II) acetylacetonate [Ni(acac)2] and methylalumoxane (MAO) catalyst was investigated. It was found that the Ni(acac)2‐MAO catalyst is effective for the copolymerization of St and IP. From the copolymerization of St (M1) and IP (M2) and IP (M2) with the Ni(acac)2‐methylalumoxane catalyst, the monomer‐reactivity ratios were determined to ber1= 1,18 andr2= 0,88, i.e., ideal copolymerization was found to proceed to give perfectly random copolymers without formation of any homopolymer. The microstructure of IP units in the copolymers exhibits high cis‐1,4 c

ISSN:1022-1336    

DOI:10.1002/marc.1995.030161101

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractBlends of poly(vinyl alcohol) (PVAI) with poly(ethyleneimine) (PEI) were prepared by casting from a common solvent. All blends show a single, composition dependent glass transition temperature (Tg), indicating that the blends are miscible in the amorphous state and in the melt. The overall crystallization rate of PVAI in the blend decreases with increasing PEI content. The crystallinity index of PVAI in the blend does not decrease greatly with PEI content up to a composition of 70/30 PVAI/PEI, since theTgof the crystallizable component PVAI is larger than that of the non‐crystallizable component PEI. TheTgof the system PVAI/PEI decreases with increasing PEI content. The interaction parameterBof the two polymers in the melt was found to be −24 J/

ISSN:1022-1336    

DOI:10.1002/marc.1995.030161102

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractPolymerization of ethylene and propene were conducted with bis(cyclopentadienylzirconium dichloride) (Cp2ZrCl2) and ethylenebis(1‐indenyl)zirconium dichloride (Et(Ind)2ZrCl2) combined with trialkylaluminium compounds using heteropolyacids as the counter‐anions, giving linear polyethylene and isotactic polypropene, respectively. No polymer was obtained when using Cp2Zr(CH3)2instead of Cp2ZrCl2. The mechanism of the formation of active species is briefly discussed on the basis of these resu

ISSN:1022-1336    

DOI:10.1002/marc.1995.030161103

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe accelerated ageing of polystyrene by means of 2‐(2‐methoxy‐5‐methylphenyl)‐2H‐benzotriazole, under conditions reproducing the outdoor environment, was studied. The results show that this benzotriazole derivative appreciably accelerates the rate of photodegradation at the surface of

ISSN:1022-1336    

DOI:10.1002/marc.1995.030161104

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractA preliminary X‐ray photoelectron spectroscopic (XPS) investigation on poly[4,4′‐isopropylidenebis(1,4‐phenyleneoxyethylene) diacrylate] samples obtained by photocuring on several substrates in the presence of a fluorine containing acrylic monomer is reported. Quantitative calculations based on F1s/C1sarea ratios and C1speak fitting show a noticeable fluorine surface enrichment that ranges, depending on the substrate, from 17 wt.‐% to 59 wt.‐% of fluorine containing moiety. The calculations also reveal the presence of a concentration gradient at

ISSN:1022-1336    

DOI:10.1002/marc.1995.030161105

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractA novel molecular model, the latent entanglement, is proposed to explain the relationships between ductilities of polyethylene reactor powders and different conditions of synthesis. According to Hoffman's variable cluster model, irregularities in the crystallite fold surface increase as the synthesis temperature is decreased. The concept of latent entanglement stems from the potentiality of these defects to convert into active entanglements when the involved chain segments are drawn out of the crystals.

ISSN:1022-1336    

DOI:10.1002/marc.1995.030161106

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractSeveral kinds of polystyrene‐supported metallocene catalysts were prepared and used in the polymerizations of propylene and ethylene with methylaluminoxane (MAO) as cocatalyst. It was found that these catalysts are stable even at 70°C. They display fairly high activities when the polymerizations are conducted at high temperatur

ISSN:1022-1336    

DOI:10.1002/marc.1995.030161107

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractA new type of aggregation behavior of block ionomers, i.e. functionalized polystyrene‐block‐poly[ethylene‐co‐(1‐butene)]‐block‐polystyrene (SEBS) with respective contents of 3.2 mol‐% and 8.3 mol‐% sodium carboxylate groups in polystyrene blocks has been studied using steady‐state fluorescence techniques. It is found that the block ionomers could form a stable dispersion in water although both the slightly ionized polystyrene block and the ethylene/1‐butene block are hydrophobic. The intensity ratio of the first to third vibronic band (I1/I3) of pyrene varies from 1.8, characteristic of the aqueous medium, to about 0.8, characteristic of hydrophobic microenvironment when the ionomer concentration in water is increased from 8 × 10−4g/L to 2 × 10−1g/L. Meanwhile, the emission intensity ratio of excimer to monomer (Ie/Im) of pyrene increases with increasing polymer concentration first, then passes through a maximum and eventually falls off to zero. Both of the methods show the same critical aggregation concentration (8 × 10−4g/L). Besides the non‐radiative energy transfer efficiency between naphthalene and anthracene shows a considerable increase when the concentration reaches 0.01 g/L. All of these three approaches lead to the fact that the block ionomers could form hydrophobic aggregates in water sta

ISSN:1022-1336    

DOI:10.1002/marc.1995.030161108

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractPropagation rate constants for the free radical polymerization of methacrylonitrile (MAN) have been obtained by pulsed laser photolysis (PLP). The temperature dependence of the propagation rate constants indicates a frequency factor of 10(6,43 ± 0,26)L · mol−1· s−1and an activation energy of 29,7 ± 1,5 kJ · mol−1. These parameters suggest that the relatively slow rate of propagation in MAN polymerization in relation to other common monomers (methyl methacrylate, styrene) can be attributed to the relative steric bulk and stability of the propagati

ISSN:1022-1336    

DOI:10.1002/marc.1995.030161109

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe anionic bulk polymerization of optically active (2R, 3S)‐3,4‐epoxy‐1,2‐O‐isopropylidenebutane‐1,2‐diol (1) and its (2S, 3S) diastereomer2was studied. Molecular weights and optical activity measurements as well as carbon and proton NMR spectra are reported. The polymers show solvent dependent inversion of the sign of optical rotation. The NMR spectra are consistent with isotactic p

ISSN:1022-1336    

DOI:10.1002/marc.1995.030161110

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY