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