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