Ring‐Opening Metathesis Polymerization of <i>endo</i>‐ and <i>exo</i>‐Norbornene Lactones
Narumi Miyasako, Shin‐ichi Matsuoka, Masato Suzuki
Abstract
Abstract New ester‐functionalized bicyclic aliphatic polymers are synthesized through the ring‐opening metathesis polymerization (ROMP) of endo ‐ and exo ‐norbornene lactones ( endo ‐NBL and exo ‐NBL) and their oxa‐norbornene analogue ( exo ‐oxa‐NBL) followed by hydrogenation. The polymerizability between endo ‐ and exo ‐NBLs, and the thermal properties between the six types of polymers before and after hydrogenation are compared and discussed. The ROMP of all three monomers proceeded in a living fashion under optimized conditions, which is confirmed by chain extension experiments. Endo ‐NBL shows a much lower homo‐ and copolymerizability than exo ‐NBL probably owing to six‐membered chelation to the Ru center and steric hindrance in the ruthenacyclobutane intermediate. Stereo‐block and stereo‐gradient copolymers of poly( endo ‐NBL) and poly( exo ‐NBL) are also synthesized. The hydrogenation catalyzed by RuHCl(CO)(PPh 3 ) 3 in the mixed solvents of o ‐xylene and N , N ‐dimethyl acetamide (DMAc) results in more than 95% conversion. The obtained hydrogenated polymers, H‐poly( endo ‐NBL) and H‐poly( exo ‐NBL), are amorphous, soluble in chlorinated aliphatic solvents, and thermally stable until 400 °C without a weight loss. Their glass transition temperatures are 163 and 131 °C, respectively; the values are appropriate in terms of both thermal stability and processing deformation for the application of transparent resin materials.