A new methodology for studying multiple-site-type catalysts for the copolymerization of olefins

A novel methodology is presented for studying the nature of multiple-site-type catalysts used for the synthesis of olefin copolymers. Experimental results of copolymer composition (short-chain branching) versus molecular weight are obtained by analyzing high-temperature gel-permeation chromatography fractions with Fourier-transform infrared spectroscopy. The molecular weight distribution obtained by gel-permeation chromatography is deconvoluted to determine the number of different site types on the catalyst. The average copolymer composition of chains made on each site type is then determined from copolymer composition versus molecular weight data. It is also shown how to extend this methodology to determine the comonomer reactivity ratios per site type.