The initiating constituent is usually present in {HEAD ~ an amount} of about 0.05 to about 5 percent by {TAIL ~ weight} of the copolymer 
The initiating constituent is usually present in { HEAD ~ an amount } of about 0.05 to about 5 percent by { TAIL ~ weight } of the copolymer
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH