Synthesis and characterization of elastoplastic poly(styrene-co-ethylene) using novel mono(?5-cyclopentadienyl) titanium and modified methylaluminoxane catalysts

Abstract

Elastoplastic poly(styrene-co-ethylene) with high molecular weight was synthesized using novel mono( 5 -pentamethylcyclopentadienyl)tribenzyloxy titanium [Cp*Ti(OBz) 3 ] complex activated with four types of modified methylaluminoxanes (mMAO) containing different amounts of residual trimethylaluminum (TMA). The ideal mMAO, used as a cocatalyst for the copolymerization of styrene with ethylene, contains TMA approaching to 17.8 wt %. The oxidation states of the titanium-active species in different Cp*Ti(OBz) 3 /mMAO catalytic systems were determined by the redox titration method. The results show that both active species may exist in the current system, where one [Ti(IV)] gives a copolymer of styrene and ethylene, and the second one [Ti(III)] only produces syndiotactic polystyrene (sPS). Catalytic activity, compositions of copolymerization products, styrene incorporation, and copolymer microstructure depend on copolymerization conditions, including polymerization temperature, Al/Ti, molar ratio, and comonomers feed ratio. The copolymerization products were fractionated by successive solvent extractions with boiling butanone and tetrahydrofuran (THF). The copolymer, chiefly existing in THF-soluble fractions, was confirmed by 13 C-NMR, GPC, DSC, and WAXD to be an elastoplastic copolymer with a single glass transition temperature.

Groups 3 and 4 single-site catalysts for styrene–ethylene and styrene–α-olefin copolymerization

“…Its structure and composition were dependent on polymerization conditions, especially the [Al]/[Ti] ratio and TMA content of the MAO. The same type of random microstructure was observed [39,40].…”

“…Very similar results were obtained with the congener catalytic system Cp*Ti(OBz) 3 /MAO: after fractionation, an elastoplastic copolymer was recovered with some PE and PS [39,40]. Its structure and composition were dependent on polymerization conditions, especially the [Al]/[Ti] ratio and TMA content of the MAO.…”