Mechanism of Isotactic Styrene Polymerization with a C6F5-Substituted Bis(phenoxyimine) Titanium System

作者：Caporaso Lucia^*; Loria Marianna; Mazzeo Mina; Michiue Kenji; Nakano Takashi; Fujita Terunori; Cavallo Luigi

来源：Macromolecules, 2012, 45(21): 8588-8597.

DOI：10.1021/ma301631b

We report a combined, experimental and theoretical, study of styrene polymerization to clarify the regio- and stereocontrol mechanism operating with a C6F5-substituted bis(phenoxyimine) titanium dichloride complex. Styrene homopolymerization, styrene propene and styrene ethene propene copolymerizations have been carried out to this aim. A combination of C-13 NMR analysis of the chain-end groups and of the microstructure of the homopolymers and copolymers reveals that styrene polymerization is highly regioselective and occurs prevalently through 2,1-monomer insertion. DFT calculations evidenced that steric interaction: between the growing chain and the monomer in the transition state insertion stage is at the origin of this selectivity. The formation of isotactic polystyrene with a chain-end like microstructure is rationalized on the base of a mechanism similar to that proposed for the syndiospecific propene polymerization catalyzed by bis(phenoxyimine) titanium dichloride complexes. Finally, a general stereocontrol mechanism operative in olefin polymerization with this class of complexes is proposed.

• 出版日期2012-11-13