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Sequence controlled ethylene/styrene copolymerization catalyzed by scandium complexes


The reported rare-earth metal based complexes catalyzed ethylene/styrene copolymerization, without expectation, to give copolymers with long syndiotactic polystyrene sequences. Here the sequence controlled ethylene/styrene copolymerization has been achieved through regulating the electronic and steric properties of scandium precursors. When a thiophene-fused cyclopentadienyl scandium complex 1, (2,4,5,6-Me4-4H-cyclopenta[b]thiophenyl)Sc(CH2SiMe3)2, was used, a copolymer with long syndiotactic polystyrene sequences was obtained. The tetrahydrofuran (THF) adduct of complex 1 (1·THF) showed a lower activity to give a copolymer with short polystyrene sequences owing to the increase of the sterics around the metal center. The pyridine adducts 1·Py and 1·PyF5 were totally inert, since the electrophilicity of the active metal center was reduced by the chelated strong Lewis base. Under the same conditions, complex 2 ((2,5-dimethyl-3-phenyl-4-H-cyclopenta[b]thiophenyl)Sc(CH2SiMe3)2), an analogue of 1, discretely incorporated styrene into the copolymer to form the “pseudo random” microstructure. Complex 3 bearing a bulky and less electron-donating CGC-ligand ((Flu-CH2−Py)Sc(CH2SiMe3)2) was able to catalyze the copolymerization in a livingness manner to afford copolymers containing mainly the alternating E/St sequence, where a fast and reversible chain transfer reaction to aluminum alkyl was observed. The influences of structural and electronic factors of the scandium precursors, such as the ligand steric bulkiness and the incorporation of Lewis base of the active metal center, on the catalytic activity and the sequence distribution of the resulting copolymers are elucidated.

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Publication details

The article was received on 12 Sep 2018, accepted on 07 Nov 2018 and first published on 08 Nov 2018

Article type: Paper
DOI: 10.1039/C8PY01326H
Citation: Polym. Chem., 2018, Accepted Manuscript
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    Sequence controlled ethylene/styrene copolymerization catalyzed by scandium complexes

    B. Liu, C. Wu and D. Cui, Polym. Chem., 2018, Accepted Manuscript , DOI: 10.1039/C8PY01326H

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