It is observed that the BADS moiety shows a negative effect on [[alpha].sub.C[O.sub.2]/[N.sub.2]], and the DABN moiety is very helpful in promoting [[alpha].sub.C[O.sub.2]/[N.sub.2]].
From Table 5, it is observed that 6FDA, MDA, BABP, and DABN moieties have positive contributions to all the ideal separation factors, while ODA, DDS, and BADS contribute negatively to [[alpha].sub.[H.sub.2]/[N.sub.2]] and [[alpha].sub.He/[N.sub.2]].
Sulfonyl groups in DDS and BADS and nitrile groups in DABN are polar groups, and they are favorable to the adsorption of polar species, e.g., water.
4, a rough sequence of monomer contributions to the pervaporation selectivity can be obtained for the monomers used in this work: DDS(-) < MDA < BADS, and DABN < BABP, the negative sign for DDS means that a negative contribution was made by the DDS moiety to the pervaporation selectivity.
ODA, MDA, and DABN moieties have smaller n values, which means that the permeation flux of the membranes containing these moieties are more sensitive to the change in the feed water content.
The flexibility of MDA, BABP, and DABN moieties, as well as the favorable interactions with water, accounts for the large contribution factors to the activation energies.
The DABN moiety was found to be favorable for improving the C[O.sub.2]/[N.sub.2] selectivity.