L1 is ##STR24## where R5 and {HEAD ~ R6} are independently a hydrogen, {TAIL ~ alkyl} or an aryl group 
are independently
L1 is # # STR24 # # where R5 and { HEAD ~ R6 } are independently a hydrogen , { TAIL ~ alkyl } or an aryl group
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH