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Abstract
We describe the synthesis of a styrene–ethylene copolymer using a trivalent titanium-based polymerization catalyst system, tris(acetylacetonate)titanium (Ti(acac)3), combined with triisobutylaluminum-modified methylaluminoxane. Gel-permeation chromatography measurement revealed that copolymerization using the above-mentioned catalyst system yielded a mixture of two different polymers. 13C nuclear magnetic resonance (NMR) analysis of the Soxhlet-extracted fractions indicated that the insoluble part contained a long ethylene–ethylene sequence and an isolated styrene unit, whereas the soluble part contained a syndiotactic styrene–styrene sequence with ethylene units adjacent to continuous styrene units. The ratio of the styrene–styrene sequence to the styrene–ethylene joint part of the Soxhlet-soluble fraction, estimated from the NMR resonances, increased with the styrene content. The melting temperature of the Soxhlet-soluble fraction also increased with the (styrene–styrene)/(styrene–ethylene) ratio of the polymers. These two results together indicate that a block-like copolymer was produced that contained long syndiotactic polystyrene portions separated by ethylene units. We describe the synthesis of a styrene–ethylene copolymer using a trivalent titanium-based polymerization catalyst system, tris(acetylacetonate)titanium/triisobutylaluminum-modified methylaluminoxane (MMAO). The catalyst system yielded a mixture of two different polymers. 13C nuclear magnetic resonance analysis of Soxhlet-extracted fractions indicated that the Soxhlet-soluble part contains the syndiotactic styrene–styrene sequence and the ethylene units adjacent to continuous styrene units. Consideration about a relation among sequence distribution, styrene content and thermal property data reasonably indicates that the block-like copolymer was produced, which contains the long syndiotactic polystyrene portions separated by the ethylene units.
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