STUDY OF ORGANOMETALLIC POLYMERIZATION CATALYSTS

Tetraneopentyltitanium initiates slow homopolymerizations and copolymerizations of styrene and of methyl methacrylate in the dark. Reactivity ratios derived from copolymer compositions indicate a free radical process. The rates of polymerizations are greatly enhanced upon irradiation. Photolysis of tetraneopentyltitanium produces trivalent titanium species as shown by EPR studies. The photolyzed products behave in the dark similarly to unphotolyzed tetraneopentyltitanium. Mechanisms for these polymerizations are discussed. Terpolymers with various degree of crosslinking were prepared. After converting the olefinic units in the crosslinked polymer into (alpha)-glycol units, the polymer support was reacted with TiCl(,4) to provide the catalyst. The activity of the catalyst toward ethylene polymerization was examined vs. crosslink density. Also studied was the swelling effect on the catalyst activity. Results indicate that catalyst activity increases with increasing rigidity of the support. However, diffusion restriction becomes important with highly crosslinked support. The chemical compositions of a MgCl(,2) supported catalyst have been determined at every stage of its preparation. Ball-milling of MgCl(,2) with ethyl benzoate resulted in the incorporation of the ester. Addition of p-cresol resulted in the retention of p-cresol. Treatment with AlEt(,3) gave a rapid reaction between AlEt(,3) and p-cresol. Further reaction with TiCl(,4) resulted in the incorporation of titanium. Activation with AlEt(,3)/methyl p-toluate complex reduces most of the Ti(\u27+4) to lower oxidation states. IR, MS, and GC-MS analyses showed quantitative reaction between p-cresol and AlEt(,3), and reduction and alkylation of the esters. Proton and carbon NMR techniques were also used to study the reaction mechanisms. EPR showed that the catalyst contains a single Ti(\u27+3) species. Activation with preformed AlEt(,c)/methyl p-toluate complex produced another single Ti(\u27+3) species having rhombic symmetry and displaying (\u2727)Al superhyperfine splitting which are attributes for a stereospecific active site. Finally, FTIR study of the solid supports, the catalyst, and the activated catalyst gave results which complement and agree with the above results