Syndiospecific living polymerization of 4‐methylstyrene and styrene with (trimethyl)pentamethylcyclopentadienyltitanium/tris(pentafluorophenyl)borane/trioctylaluminum catalytic system

The polymerizations of styrene and 4‐methylstyrene (4MS) with a half‐metallocene type catalytic system composed of (trimethyl)pentamethylcyclopentadienyltitanium (Cp*TiMe3), trioctylaluminum (AlOct3), and tris(pentafluorophenyl)borane [B(C6F5)3] were investigated at −25 °C. The addition of AlOct3as a third component of the catalytic system is effective both to promote the syndiospecific polymerization and to inhibit the nonstereospecific polymerization at the low‐temperature region. The use of AlOct3was also effective to eliminate the chain transfer reaction to alkylaluminum. The number‐average molecular weights (Mn's) of poly(4MS) or polystyrene increased proportionally with increasing monomer conversion. The molecular weight distribution (MWD) of polymer stayed narrow [Mw/Mn= ∼ 1.1 for poly(4MS) andMw/Mn= ∼ 1.5 for polystyrene]. It was thus concluded that the polymerizations of the styrenic monomers with Cp*TiMe3/B(C6F5)3/AlOct3catalytic system proceeded under living fashion at −25 °C. The living random copolymerization behaviors of styrene and 4MS were also confirmed. The13C NMR analysis clarified that each of the homopolymers and random copolymers obtained in this work had highly syndiotactic structure.