Vinylcyclohexane (VCH) was polymd. in the presence of catalytic systems based on zirconocenes belonging to a C2, C2υ or Cs symmetry group. All polymers were analyzed by 13C NMR spectroscopy and showed an isotactic microstructure. A steric control mechanism, involving a like 1,3-asym. induction of the chiral carbon of the last inserted unit on the chirality of the incoming monomer coordination, is proposed. This would be the only stereocontrol mechanism in the presence of a C2υ-symmetry catalyst, and it would enforce or overcome site control in the case of active species with C2 and Cs-symmetry, resp.
Polymerizations of vinyl-cyclohexane in the presence of C2, C2v, and Cs zirconocene-based catalysts
GRISI, Fabia;PRAGLIOLA, Stefania;COSTABILE, Chiara;LONGO, Pasquale
2006-01-01
Abstract
Vinylcyclohexane (VCH) was polymd. in the presence of catalytic systems based on zirconocenes belonging to a C2, C2υ or Cs symmetry group. All polymers were analyzed by 13C NMR spectroscopy and showed an isotactic microstructure. A steric control mechanism, involving a like 1,3-asym. induction of the chiral carbon of the last inserted unit on the chirality of the incoming monomer coordination, is proposed. This would be the only stereocontrol mechanism in the presence of a C2υ-symmetry catalyst, and it would enforce or overcome site control in the case of active species with C2 and Cs-symmetry, resp.File in questo prodotto:
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