Aqueous ring-opening metathesis polymerization of carboximide-functionalized 7-oxanorbornenes

The ring-opening metathesis polymerization (ROMP) of exo-N-methyl-7-oxabicyclo[2.2.1]-hept-5-ene-2,3-dicarboximide (1) was accomplished in aqueous solution under mild conditions using the simple ruthenium(II) coordination complex Ru^(II)(H_2O)_6(tos)_2 (tos = p-toluenesulfonate) (2). The polymerization yield was nearly quantitative. The resultant high molecular weight polymer (poly-1) exhibited a glass transition temperature (T_g) of 225 °C and was thermally stable up to 402 °C. The thermal and radiative stabilities of poly-1 were further investigated. Poly-1 was hydrogenated to yield its saturated analogue, which had a lower T_g (170 °C) but a higher temperature of decomposition (430 °C). Complex 2 was deactivated by coordination of free maleimides formed during the polymerization of carboximide-functionalized monomers capable of undergoing retro Diels-Alder chemistry. The scope of this polymerization was therefore limited to carboximide-functionalized monomers that are stable toward retro Diels-Alder reactions at the polymerization temperature. Both ruthenium (II)-1 and ruthenium(II)-N-methylmaleimide olefin complexes were identified