1, DDS and MDA have molecular structures similar to ODA, and the only difference lies in the sulfonyl group and the methylene bond, respectively, instead of the ether bond in ODA, while BADS, BABP, and DABN have 3-amino-phenyl moieties in the molecules.
Using MOPAC, Wang-Ford charges were determined: ODA (-0.940) > BABP (-0.932), BADS (-0.931), DABN (-0.930) > MDA (-0.926) > DDS (-0.920).
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]].
The acyl groups in BABP can form hydrogen bonds with water, and hence the permeation of water in the BABP moiety-containing membranes will benefit more from sorption.
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.
BABP moieties can form favorable interactions with water, and a better sorption can be achieved.
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.