Homogeneous single-site catalysts for olefin polymerization offer potential control of the various kinetic steps, which in turn can be tuned by “catalyst design.” To achieve this level of control the rate constants for all steps in the catalytic cycle must be resolved. The evolution of molecular weight distribution (MWD) is a powerful tool containing a record of all the events occurring during polymerization. Nevertheless, it has not been used to its full potential in building kinetic models until now. When the MWD is combined with a rich multi-response data set of monomer consumption, active site counting, and end group analysis, previously unrealized mechanistic aspects of metal-dependent insertion polymerization are uncovered and robust rate constants can be obtained. This presentation will illustrate how structural changes in titanium, zirconium, and hafnium coordination catalysts affect chain transfer and propagation of 1-hexene polymerization. Changes in activator concentration that result in nonlinear behavior is seldom understood. We have been able to elucidate selective degenerative group transfer as a mechanism for obtaining faster initiation and narrower MWD when substoichiometric activator concentrations are used. The prospect for quantitative kinetic modeling in “catalyst design” will be discussed.

Kinetics of metal-dependent insertion polymerization of 1-hexene

251st National Meeting (2016)

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