茂金属催化剂对乙烯/丙烯共聚物序列分布的影响OA

This study investigated how five metallocene catalysts M1-M5 controlled the sequence distribution of ethylene/propylene copolymers.It used density functional theory at the B3LYP level with a polarizable continuum solvation model.Monomer insertion energy barries,transition state geometric parameters,and energy gradients were calculated.The study validated these computational results using 13C NMR.The results show that first ethylene insertion with significantly lower energy barries(15.5 kcal/mol)than propylene(18.5 kcal/mol).The binary sequence distributions exhibit a pronounced negative correlation with the total energy barries of two consecutive insertions.This correlation confirms an energy-dominated control mechanism.Ternary sequence distribution requires additional structural parameters of the transition state,such as steric and electronic effects.In summary,energy and structural parameters synergistically control the sequence distribution of copolymers,providing a theoretical basis for the design of high-performance polyolefin catalysts.