Addition copolymerization of norbornene lactone catalyzed by Pd complexes |
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Authors: | Kosuke Isaji Shin-ichi Matsuoka Masato Suzuki |
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Institution: | Department of Life Science and Applied Chemistry, Graduate School of Engineering, Nagoya Institute of Technology, Nagoya, Japan |
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Abstract: | The addition copolymerization of norbornene (NB) with functionalized monomers can lead to the modification of physical properties of poly(NB). Herein, the synthesis of new copolymer of NB with exo-norbornene lactone (exo-NBL) is reported. The copolymerization proceeded by four Pd catalytic systems, and of these, Pd(allyl)IDippCl/AgSbF6 (IDipp = 1,3-bis2,6-diisopropylphenyl]imidazolin-2-ylidene)) was the most effective for the incorporation of exo-NBL. Specifically, the copolymerization with exo-NBL/NB feed ratio of 50/50 at r.t. by 0.1 mol% of the Pd catalyst produced poly(NB-co-exo-NBL) with Mn of 87,000, and Mw/Mn of 1.2 in 40% yield, incorporating exo-NBL of 18 mol%. The time–conversion plots and 1H diffusion ordered spectroscopy (DOSY) NMR analysis of the copolymer suggest that it has a random sequence. In contrast, no copolymer was formed from endo-NBL. This is because of steric hindrance of the endo-lactone moiety by considering the (co)polymerization of endo-5-norbornene-2-carboxylic acid methyl ester (endo-NBCO2Me). The incorporation of exo-NBL improves the solubility of poly(NB-co-exo-NBL) in several chlorinated solvents and gives high thermal stability with 10% weight loss at a temperature of more than 400°C. Two amorphous halos corresponding to intra- and interchain distances were observed in the WAXD patterns, allowing to calculate d-spacing values, which are higher than that of poly(NB). |
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Keywords: | addition polymerization coordination polymerization norbornene lactone palladium catalyst |
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