The membrane 1 which is {HEAD ~ the polyimide} from pyromellitic dianhydride and {TAIL ~ 4,4 diaminodiphenyl ether} 
The membrane 1 which is { HEAD ~ the polyimide } from pyromellitic dianhydride and { TAIL ~ 4,4 diaminodiphenyl ether }
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL