Ethylene was polymerized at 5 bar in a stirred powder bed reactor with silica supported r~c-Me~Si[Ind]~ZrC1~/rnethylaluminoxane (MAO) at temperatures between 40 "C and 80 "C using NaCl as support bed and triethylaluminium (TEA) as a scavenger for impurities. For this fixed recipe and a given charge of catalyst, the average catalyst activity is reproducible within 10% for low temperatures. The polymerization rate and the rate of deactivation increase with increasing temperature. The deactivation could be modeled using a first order dependence with respect to the polymerization rate.
Cationic starch, cationic cellulose derivatives, and hydrophobically modified cationic cellulose were physically adsorbed from aqueous solution onto oppositely charged hydrophobic polyester (poly(ethylene terephthalate)) fabric and nonwoven, and this resulted in hydrophilic surface properties. Surface coverage of the polysaccharides occurred primarily by strong electrostatic interactions, and the surface characteristics were evaluated by measuring the time required for a water droplet to be absorbed into the polyester material as well as by electron spectroscopy for chemical analysis (ESCA). From a comparison of the adsorption characteristics we assess the polysaccharide-dependent and substrate-dependent adsorption behavior and discuss the similarities and differences in the hydrophilic properties and wettability observed. In particular, the temperature of the cationic polysaccharide solutions in which the substrate was immersed, the configuration of the polymer in solution, and the presence of hydrophobic substituents on the cationic moiety have a considerable effect on the polysaccharide affinity and its adsorption on the surface, irrespective of the substrate type (fabric or nonwoven). We also evaluate the relative contribution of the polyelectrolyte molecular weight, concentration in solution, and degree of charge density along the polymer chain which determine the range of interactions and alter surface hydroplilicity dependent on the type of substrate.
New Cyclooctatetraene Complexes of Niobium[1]
The (butadiene)niobium complexes Cp′Nb(C4H6)2 and Cp′Nb(C4H6)(PMe3)2 (Cp′C5H4Me) react with cyclooctatetraene (COT) to give Cp′Nb(C4H6)(COT) (2), Cp′Nb(COT)2 (3), and Cp′Nb(PMe3)2(COT) (5) with fluxional COT ligands. The structure of 3 exhibits a prone‐η3‐ and a supine‐η4‐COT ligand which interchange their role at elevated temperature. That of 5 shows a supine η3‐COT ligand.
The known bis(butadiene)(cyclopentadienyl)niobium complex (C5H4R)Nb(C4H& (1, R = H) exists in solution as a 1: 1 mixture of a bis(cis-butadiene) isomer 1 a and a (cis-butadiene)(transbutadiene) isomer 1 b. In solution the barrier to isomerisation is 80 f 2 kJ/mol. New derivatives 2 (R = Me) and 3 (R = SiMe3) of 1 are described. One of the butadiene ligands in 1 -3 is readily substituted with CO, CNfBu, P(OMe)3, and PMe3. CpNb(PMe3),(C4H6) (?) reacts with disubstituted acetylenes to form acetylene complexes CpNb(PMe3)(C,HG)(RC = CR') ( 8 R, R' = Ph, 9 R = Me, R' = Ph, and 10: R = Ph, R = SiMe3). The structure of 9 resembles that of bent metallocene derivatives with the acetylene acting as a 2-e ligand.(Butadien)(cyclopentadienyl)metall-Komplexe friiher dMetalle waren in den letzten Jahren Gegenstand intensiver systematischer Erforschung*). Schwerpunkte lagen bei Komplexen des Typs C~,Zr(butadien)~), CpTa(butadien);) und C~Mo(NO)(butadien)~). Komplexe des Typs CpNb(butadienh sind weniger gut bekannt6
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