Effects of Catalyst Activation, Deactivation, and Active Site Physical Residential Environment on Ethylene−α-Olefin Elastomeric Copolymerization

This study investigates the effects of precatalyst-cocatalyst structure, α-olefin type, temperature, and catalyst active site physical residential environment on ethylene−α-olefin elastomeric copolymerization; catalyst activation, deactivation, and dormancy; and copolymer average composition, microstructure, reactivity ratios, and phase morphology. The copolymerization was conducted using a Spaleck metallocene and a Dow CGC Post-metallocene, separately preactivated with methylaluminoxane and tritylborate-excess triisobutyl aluminum cocatalysts. Five pending catalytic issues were addressed. Modeling ethylene solubility and the liquid phase compressibility factor quantified catalyst active site physical residential environment. The predicted ethylene solubilities, matching experimental data, correct the error that occurs, in calculating monomer−α-olefin reactivity ratios, due to ignoring copolymerization propagation kinetics and ethylene concentration. Catalyst active site physical residential environment and the polymeryl pseudo-single site catalyst concept, introduced herein, better address catalyst activation, deactivation, and dormancy; copolymerization mixture ensemble; MW−temperature relation; and MWD broadening. This work correctly elucidates the origin of elastomer phase morphology and the role that the α-olefin side chain flexibility plays to regulate T_g. The catalyst ion-pair concept was especially evaluated by studying the macroscopic vs. microscopic catalyst deactivation and dormancy. The elastomer inter-backbone interaction was modeled. The present study results will help design and develop better catalysts and processes for making gaseous monomer−α-olefin elastomers.