Preferably, {HEAD ~ the polymer} has {TAIL ~ a molecular weight} in the range of 100 Da to 800 kDa 
has
Preferably , { HEAD ~ the polymer } has { TAIL ~ a molecular weight } in the range of 100 Da to 800 kDa
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