Syntheses of multi-stereoblock polybutene-1 using novel monocyclopentadienyltitanium and modified methylaluminoxane catalysts

Butene-1 was polymerized using novel mono-(η⁵-pentamethylcyclopentadienyl) tribenzyloxy titaniumCp*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