Polynorbornene dicarboximides with cyclic pendant groups:: Synthesis and gas transport properties

The synthesis of new N-cyclopentyl-exo,endonorbomene-5,6-dicarboximide (CpNDI) (3a) and N-cyclohexyl-exo,endo-norbomene-5,6-dicarboximide (ChNDI) (3b) monomers was carried out. From these monomers, two polynorbornene dicarboximides with cyclopentyl and cyclohexyl pendant groups, poly(exo,endo-N-cyclopentyl norbornene-5,6-dicarboximide) (PCpNDI) and poly(exo,endo-N-cyclohexyl norbonene-5,6-dicarboximide) (PChNDI), respectively, were synthesized by ring opening metathesis polymerization (ROMP). PCpNDI, which bears a cyclic pentyl moiety, shows a higher T-g and mechanical properties compared to PChNDI. A comparison of density, fractional free volume, and gas permeability coefficients of the synthesized polynorbornenes shows that PCPNDI presents a slightly higher density and lower fractional free volume than PChNDI. It was also found that gas permeability coefficients for PCpNDI are lower than those of PChNDI. In all cases, the selectivity followed the usual trade-off found in other glassy polymers: as gas permeability coefficients increase selectivity decreases.