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