Synthesis and characterization of elastoplastic poly(styrene-co-ethylene) using novel mono(η5-cyclopentadienyl) titanium and modified methylaluminoxane catalysts
✍ Scribed by Fangming Zhu; Yutang Fang; Shangan Lin
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 153 KB
- Volume
- 74
- Category
- Article
- ISSN
- 0021-8995
No coin nor oath required. For personal study only.
✦ Synopsis
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.