The Origin of Living Polymerization

To gain information on the origin of this unprecedented living polymerization, we investigated the ethylene polymerization behavior of various fluorinated Ti-FI catalysts 16-18, 40, and 48-51 (Fig. 30). 

It should be pointed out that a structurally related bis(imine-phenoxy)Ti complex 54 (Fig. 32) having a C6F5 on the imine-N with MAO activation does not initiate living ethylene polymerization. Interestingly, DFT calculations suggested that there is virtually no interaction between the ortho-F and the 3-H (ortho-F/ 3-H distance 3.66 A) (Fig. 33) [21]. 

Based on the results and discussions described so far, we concluded that the steric bulk provided by the ortho-F does not play an important role and that the attractive non-bonding interaction of the ortho-F with the 3-H of the growing polymer chain is responsible for the unprecedented living polymerization, representing the first example of an attractive interaction between the ligand and other components in a catalyst system, which dramatically enhances catalyst performance [35, 68, 74, 75]. 

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