Investigation of exo- and endo-isomers of 5-norbornene-2,3-dicarboxylic anhydride in ethylene copolymerization†

Polar norbornene-based monomers represent an important class of comonomers in ethylene copolymerization, and their exo/endo isomers usually exhibit different reactivity during the polymerization process. In this contribution, we first report that the exo-isomer of 5-norbornene-2,3-dicarboxylic anhydride (CA) can be more efficiently copolymerized with ethylene than its endo-isomer and exhibit higher polymerization activities, higher incorporations and higher molecular weights using phosphine-sulfonate palladium catalysts. Kinetic studies further confirmed that the polymerization rate of the exo-isomer of CA was faster than that of the corresponding endo-isomer. In addition, the properties of the obtained copolymers were investigated, including surface, mechanical, adhesive and compatibilizing properties. In particular, the copolymer of ethylene and the exo-isomer of CA with an incorporation of 6.0 mol% exhibited a better compatibilizing performance than the commercial compatibilizer for polyamide-6 and polyolefin elastomer blends.