No abstract

AImtraet--Stable cationic latices were prepared by emulsifier-free emulsion polymerization of styrene with 1-methyl-4-vinylpyridinium bromide or 1-methyl-4-vinylpyridinium iodide as comonomers using azobis(isobutyramidine hydrochloride) as initiator. Comonomers were prepared by a new and simple synthetic procedure. Addition of methanol and especially comonomer increased the surface charge density of cleaned latices and enhanced the polymerization rate. In the presence of iodide, the polymerization rate was lowered. The co-catalytic properties of silica-cleaned latices on the oxidative coupling of 2-mercaptoethanol were tested after cobalt(II)phthalocyanine-tetrasodiumsulphonate (CoTSPc) immobilization onto the functionalizod latex particles. A significant increase in oxidation rate was found as compared with the polymer-free CoTSPc system.

Complexes of the tetrasodium salt of cobalt(I1)-tetrasulfophthalocyanine and poly(viny1amine) were applied as bifunctional catalysts for the autoxidation of thiols to disulfides. Optical and catalytic experiments gave supporting evidence to the hypothesis, that the isolation of cobalt centers and the catalytic activity can be promoted by increasing the relative amount of polymeric base. It appeared that the specific catalytic activity of the polymeric catalysts depends on the number average degree of polymerization (F,) of the applied polymer samples. In particular at relatively high cobalt content, samples with comparatively low Fn give more protection against aggregation of cobalt sites (i.e. inactivation) and, therefore, effect a higher specific catalytic activity. A statistical calculation, suitable to determine the distribution of cobalt sites over the polymeric coils, supports the interpretation of the experimental data.

In order to obtain insight into the structure of cobalt phthalocyanine dimers, molecular mechanics calculations were performed on dimeric cobalt phthalocyanine species. Molecular mechanics calculations are first presented on monomeric cobalt(H) phthalocyanine.Using the Tripos force field for the organic part of the molecule and parameters derived from the literature and subsequently optimized to describe the Co" force field resulted in a geometry that is in very good agreement with experimental data from the literature. Optimization of the dimeric structure leads to a geometry in which both phthalocyanines are separated by 3.2 A and one of the molecules is shifted 2.38 A in both the X-and Y-directions with respect to the other. This geometry is in excellent agreement with literature data on fi-Co(pc) crystals and with other calculated and experimental data on similar systems. All calculations were performed with three possible charge distributions in the phthalocyanine molecule and it was shown that varying the charge distribution had no significant effect on the final dimeric structure. This method provides valuable insight into the most important energetic interactions leading to dimer formation.

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