A. Morisato et al., GAS SEPARATION PROPERTIES OF AROMATIC POLYAMIDES CONTAINING HEXAFLUOROISOPROPYLIDENE GROUPS, Journal of membrane science, 104(3), 1995, pp. 231-241
The synthesis and gas transport properties of aromatic polyisophthalam
ides (PIPAs), based on isophthaloyl chloride derivatives bearing pende
nt groups and hexafluoroisapropylidene (6F) linkages in the main chain
, are reported and compared with properties of a similar series of PIP
As containing sulfonyl (SO2) rather than 6F in the main chain. All of
these polymers exhibit high glass transitions temperatures. The polyme
rs containing 6F groups were markedly more permeable and somewhat less
selective than their sulfonyl analogs. Polymers containing a t-butyl
pendent group at the 5 position of the isophthaloyl linkage were much
more permeable than those bearing only a hydrogen atom at this positio
n, although a strong decrease in permselectivity accompanied the large
increase in permeability. CO2/CH4 solubility selectivity values of th
e BF-containing polymers were similar to values reported for other pol
ymeric and non-polymeric organic materials with similar concentrations
of polar carbonyl linkages. In contrast, the CO2/CH4 solubility selec
tivity in SO2-containing variants of these polymers was substantially
lower than expected based on total polar group concentration. The low
CO2/CH4 solubility selectivity is believed to be related to the extrem
ely efficient chain packing in the SO2-containing polymers, which may
lead to strong amide-amide linkage interaction, thereby inhibiting car
bonyl groups in the amide linkage from interactions with CO2 molecules
to increase CO2/CH4 solubility selectivity.