Copolymerization of norbornene and 5-norbornene-2-yl acetate using novel bis(β-ketonaphthylamino)Ni(II)/B(C₆F₅)₃/AlEt₃ catalytic system
2009
He, Fuping | Chen, Yiwang | He, Xiaohui | Chen, Muqing | Zhou, Weihua | Wu, Qing
Vinyl-type copolymerization of norbornene (NBE) and 5-NBE-2-yl-acetate (NBE-OCOMe) in toluene were investigated using a novel homogeneous catalyst system based on bis(β-ketonaphthylamino)Ni(II)/B(C₆F₅)₃/AlEt₃. The copolymerization behavior as well as the copolymerization conditions, such as the levels of B(C₆F₅)₃ and AlEt₃, temperature, and monomer feed ratios, which influence on the copolymerization were examined. Without combination of AlEt₃, the catalytic bis(β-ketonaphthylamino)Ni(II)/B(C₆F₅)₃ exhibited very high catalyst activity for polymerization of NBE. Combination of AlEt₃ in catalyst system resulted in low conversion for polymerization of NBE. For copolymerization of NBE and NBE-OCOMe, involvement of AlEt₃ in catalyst is necessary. Slight addition of NBE-OCOMe in copolymerization of NBE and NBE-OCOMe gives rise to significant increase of catalyst activity for catalytic system bis(β-ketonaphthylamino)Ni(II)/B(C₆F₅)₃/AlEt₃. Nevertheless, excess increase of the NBE-OCOMe content in the comonomer feed ratios results in decrease of conversion as well as activity of catalyst. The achieved copolymers were confirmed to be vinyl-addition copolymers through the analysis of FTIR, ¹H NMR, and ¹³C NMR spectra. ¹³C NMR studies further revealed the composition of the copolymer and the incorporation rate was 7.6-54.1 mol % ester units at a content of 30-90 mol % of the NBE-OCOMe in the monomer feeds ratios. TGA analysis results showed that the copolymer exhibited good thermal stability (Td > 410 °C) and failed to observe the glass transitions temperature over 300 °C. The copolymers are confirmed to be noncrystalline by WAXD analysis results and show good solubility in common organic solvents.
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