Syntheses of Multi-stereoblock Polybutene-1 Using NovelMonocyclopentadienyltitanium and ModifiedMethylaluminoxane Catalysts
Butene-1 was polymerized using novel mono-(h5-pentamethylcyclopentadienyl)
tribenzyloxy titanium[Cp*Ti(OBz)3] complexes activated with three types of modified
methylaluminoxanes (mMAO) containing different amounts of residual trimethylaluminum
(TMA). The oxidation states of titanium in different Cp*Ti(OBz)3 and
mMAO catalytic systems were determined by redox titration method. The influences of
various oxidation state of titanium active species on butene-1 polymerization were
investigated. It is found that Ti(IV) active species is in favour of producing polybutene-
1. The polymer obtained at 0°C and 30°C with melting temperature was shown
by 13C-NMR and DSC characterizations to comprise of multiple blocks of isotactic and
atactic segments. 13C-NMR analyses of polybutene-1 implies that chain propagation of
butene-1 involves primarily head-to-tail 1,2-insertions, with involving negligible proportion
of head-to-head and tail-to-tail 2,1-misinsertions. There is a remarkable decrease
in 2,1-misinsertions with decreasing temperature of polymerization. © 1999 John
Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4497–4501, 1999