Second, recovering {HEAD ~ the metallated polymer} in the active form allows {TAIL ~ concentration} thereof for further reaction 
Second , recovering { HEAD ~ the metallated polymer } in the active form allows { TAIL ~ concentration } thereof for further reaction
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH