{TAIL ~ The polyalkylene glycol} must have {HEAD ~ a relatively low molecular weight}, preferably below about 2000 
{ TAIL ~ The polyalkylene glycol } must have { HEAD ~ a relatively low molecular weight } , preferably below about 2000
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH