As noted, one of {TAIL ~ the dicarboxylic acids} must have {HEAD ~ an aryl group}, which acid would include but not be limited to terephthalic acid and isophthalic acid 
As noted , one of { TAIL ~ the dicarboxylic acids } must have { HEAD ~ an aryl group } , which acid would include but not be limited to terephthalic acid and isophthalic acid
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH