Syndiospecific living polymerization of 4-methylstyrene and styrene with (trimethyl)pentamethylcyclopentadienyl-titanium/tris(pentafluorophenyl)borane/trioctylaluminum catalytic system

The polymerizations of styrene and 4-methylstyrene (4MS) with a half-metall ocene type catalytic system composed of (trimethyl)pentamethylcyclopen-tadi enyltitanium (Cp*TiMe3), trioctylaluminum (Aloct(3)), and tris(pentafluorop henyl)borane [B(C6F5)(3)] were investigated at -25 degreesC. The addition o f AlOct(3) as a third component of the catalytic system is effective both t o promote the syndiospecific polymerization and to inhibit the nonstereospe cific polymerization at the low-temperature region. The use of AloCt(3) was also effective to eliminate the chain transfer reaction to alkylaluminum. The number-average molecular weights (M-n's) of poly(4MS) or polystyrene in creased proportionally with increasing monomer conversion. The molecular we ight distribution (MWD) of polymer stayed narrow [M-w/M-n = similar to 1.1 for poly(4MS) and M-w/M-n = similar to 1.5 for polystyrene]. It was thus co ncluded that the polymerizations of the styrenic monomers with Cp*TiMe3/B(C 6F5)(3)/AlOCt(3) catalytic system proceeded under living fashion at -25 deg reesC. The living random copolymerization behaviors of styrene and 4MS were also confirmed. The C-13 NMR analysis clarified that each of the homopolym ers and random copolymers obtained in this work had highly syndiotactic str ucture. (C) 2001 John Wiley & Sons, Inc.