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