More preferably, {HEAD ~ the polymer} has {TAIL ~ a molecular weight} no greater than 60 kDa 
has
More preferably , { HEAD ~ the polymer } has { TAIL ~ a molecular weight } no greater than 60 kDa
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH