During {TAIL ~ the polymerization} of the monomers required to form the polyethylene terephthalate, a quantity of {HEAD ~ polyethylene glycol} is copolymerized therewith to form a polymer which exhibits a substantial intrinsic viscosity  
During { TAIL ~ the polymerization } of the monomers required to form the polyethylene terephthalate , a quantity of { HEAD ~ polyethylene glycol } is copolymerized therewith to form a polymer which exhibits a substantial intrinsic viscosity
OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH