The synthesis and polymerization of the new monomers N-(1-adamantyl)-exo-norbornene-5,6-dicarboximide (AdNDI), N-cyclohexyl-exo-norbornene-5,6-dicarboximide (ChNDI), and N-phenyl-exo-norbornene-5,6-dicarboximide (PhNDI) are reported. Copolymers of N-(1-adamantyl)-exo-norbornene-5,6-dicarboximide/norbornene, with molar compositions 50/50, 70/30, and 30/70, were also obtained. The
transport of hydrogen, oxygen, nitrogen, carbon monoxide, carbon dioxide, methane, ethylene, and ethane
across membranes prepared from these homopolymers and copolymers was determined at 30 °C using
permeation techniques. Diffusion coefficients correlate rather well with the diameter of diffusant molecules
except in the case of carbon dioxide. The values of the permselectivity coefficient for different gases depend
on the type of membranes. For example, the permselectivity of oxygen with respect to nitrogen, α(O2/N2),
is ca. 5.50 for membranes prepared from N-(1-adamantyl)-exo-norbornene-5,6-dicarboximide/norbornene
(50/50) copolymers, which compares favorably with the values reported for this parameter in membranes
with imide groups located in the backbone. The values of α(H2/C2H6) in membranes of poly(N-(1-adamantyl-exo-norbornene-5,6-dicarboximide), poly(N-cyclohexyl-exo-norbornene-5,6-dicarboximide), and poly(N-phenyl-exo-norbornene-5,6-dicarboximide) are 183, 124, and 122, respectively, whereas the values of
α(C2H4/C2H6) amount to 6.9, 7.6, and 6.4, respectively. For most membranes used in this study, diffusion
rather than solubility is responsible for the discrimination of gas transport. However, solubility is mainly
responsible for the high permselectivity of ethylene with respect to ethane displayed by the membranes.
