Most preferably, {HEAD ~ the polymer} has {TAIL ~ a molecular weight} in the range of 15 kDa to 40 kDa 
has
Most preferably , { HEAD ~ the polymer } has { TAIL ~ a molecular weight } in the range of 15 kDa to 40 kDa
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH