摘要:

AbstractLanthanum isopropoxide was found to serve as a novel anionic initiator for the polymerization of hexyl isocyanate affording poly(hexyl isocyanate) with very high molecular weight (Mn>106) under appropriate conditions. Other lanthanoid alkoxides, such as samarium, ytterbium and yttrium isopropoxides, also brought about the polymerization of hexyl isocyanate. Butyl, isobutyl, octyl andm‐tolyl isocyanates also underwent the polymerization reaction to form the corresponding polymers by using lanthanum isopropoxide as initiator, while polymerizations oftert‐butyl and cyclohexyl isocyanates with lanthanum isopropoxide did not occur under identical conditi

ISSN:1022-1336    

DOI:10.1002/marc.1996.030170101

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractInversion of stereoselectivity of a particular metallocene (Me2Si(Flu) (N‐t‐Bu)ZrCl2) (Me: methyl, Flu: fluorenyl,t‐Bu:tert‐butyl) from syndiospecific into isospecific was observed by changing the cocatalyst from methylaluminoxane (MAO) to [Ph3C]+[B(C6F5)4]−/AliBu3(iBu:isobutyl). The change of the solvent‐separated ion pair (in case of MAO as cocatalyst) into the contact ion pair (in case of the more polar and less bulky borate anion) was proposed as the plausible explanation of this

ISSN:1022-1336    

DOI:10.1002/marc.1996.030170102

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

Abstract2‐Mercaptobenzyl alcohol and 4‐mercaptobenzyl alcohol were synthesized in good yields starting form thiosalicylic acid andp‐toluenesulfonic acid, respectively. Poly(vinyl chloride) (PVC) reacts selectively with the thiol group of these bifunctional compounds leading to modified PVC with free hydroxy groups. In a second step the polymer chains can be partially crosslinked by reaction with hexamethylene diisocyanate. According to the degree of PVC modification, the network density of the resulting elastomers is freely adjus

ISSN:1022-1336    

DOI:10.1002/marc.1996.030170103

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractA modified‐polypropene‐supported Ziegler catalyst was prepared using polypropene containing a small amount of poly(7‐methyl‐1,6‐octadiene) as a starting polymer for bromination, lithiation, and reaction with TiCl4. The polymerization of ethene was carried out using the catalyst with Al(C2H5)3in toluene at 60°C up to 100 h. The polymer yield increased linearly with polymerization time, which indicates that the active sites of the modified‐polypropene‐supported Ziegler catalyst are practically stable without deactivation even for 100 h and are able to propagate further polymeriza

ISSN:1022-1336    

DOI:10.1002/marc.1996.030170104

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe following values of monomer reactivity ratios were found:rS= 3,3 ± 0,3;rB= 0,12 ± 0,02 (cyclohexane, 25 °C). The comparison of the kinetic parameters obtained with Li, Na and K counter‐ions shows that the great difference between coordination polymerization with Li and “typically anionic” polymerization with K is mainly determined by the variation of the cross‐propagation rate constantkBSwith the nature of the counter‐ion. No evidences for the specific role of the solvation of Li counter‐ion with butadiene mono

ISSN:1022-1336    

DOI:10.1002/marc.1996.030170105

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractA facile synthesis of linear monodisperse hydroxyl‐containing polystyrene, poly{styrene‐co‐[p‐(1‐hydroxyethyl)styrene]} and poly{styrene‐co‐[p‐(2‐hydroxypropan‐2‐yl)styrene]}, was carried out via chemical modification of polystyrene by a two‐step procedure, i. e. monodisperse polystyrene was acetylated under mild conditions, followed by processes of reduction with LiAlH4and addition with CH3MgBr, respectively.1H NMR and FTIR spectra showed that in both cases, the reaction of acetyl to hydroxyl is complete. Sizeexclusion chromatography demonstrated that both molecular weight and monodispersity of the final products w

ISSN:1022-1336    

DOI:10.1002/marc.1996.030170106

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe influence of crosslinking conditions (γ‐radiation‐induced and chemical crosslinking above and below the clearing point) on the phase behavior of a liquid‐crystalline polyacrylate‐based elastomer is shown and discussed. The network formation in samples γ‐irradiated in the nematic phase results in an increase of the clearing pointTn‐iwhich does not depend on the crosslinking density expressed as the ratio of weight‐average molecular weight over number‐average molecular weight between crosslinksMw/Mcwithin a wideMw/Mcrange. The distorting action of the crosslinking agent at the same temperature leads to the opposite tendency in the change ofTn‐i. Crosslinking in the isotropic phase shows a str

ISSN:1022-1336    

DOI:10.1002/marc.1996.030170107

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractSeveral types of poly(silamine)s were prepared and their structure‐characteristics relationships were investigated. When a phenyl ring in the organosilyl unit and/or a cyclic structure in the amino unit was introduced, the glass transition temperatures were increased significantly in order to increase film formability. From the thermogravimetric analysis of the poly(silamine)s, it was found that the thermal decomposition of poly(silamine)s starts at ca. 380–400°C. On electron‐beam irradiation of the poly(silamine) films, degradation of the polymer took place. On the basis of these results, poly(silamine)s can be one of the candidates for new positive‐type polymeric

ISSN:1022-1336    

DOI:10.1002/marc.1996.030170108

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractWe report the characterization of a sample of poly(ethylene glycol) (PEG,Mn= 3841,Mw/Mn= 1.01), and its derivative end‐labeled with pyrenebutyrate groups, using high resolution MALDI time‐of‐flight mass spectrometry. A matrix of 2‐(4‐hydroxyphenyl‐azo)benzoic acid containing a trace of either sodium chloride or potassium chloride was employed for laser desorption. Peaks due to the sodium or potassium cationized polymers were obtained, equally spaced at 44 mass units apart. For the pyrenebutyrate diester, the analysis shows that 80 ± 2% of the chains were doubly labeled, with the ramaining chains containing only a single pyrene group. Molecular weight determinations for both sets of samples were entirely consistent with size‐exclusion chromatography measurements, but were obtained with greater accuracy and less ambiguity about the influence of the end groups on the hydrodynamic radius

ISSN:1022-1336    

DOI:10.1002/marc.1996.030170109

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractWe have undertaken the molecular imprinting of Leu5‐enkephalin, and derivatives related to this endogenous neuropeptide, in highly cross‐linked methacrylic acid/ethylene dimethacrylate copolymers. The underivatized enkephalin peptide yielded polymers with poor recognition abilities, since the imprinting of this compound had to be performed using dimethyl sulfoxide, which was found to interfere with the imprint inducement, as the solvent of polymerisation. In order to circumvent this problem, the amino‐ and carboxy‐protected derivatives Boc‐Leu5‐enkephalin and Leu5‐enkephalin anilide, which are soluble in apolar solvents, were investigated as alternative imprint molecules. Both compounds led to polymers which are highly specific for the imprint species. The anilide derivative was shown to be a good substitute for the free peptide since the resultant polymers showed efficient recognition of the parent enkepha

ISSN:1022-1336    

DOI:10.1002/marc.1996.030170110

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY