{TAIL ~ R4} is H, CN, {HEAD ~ C1 C18 alkyl}, C1 C18 perfluoroalkyl, CH2 SO3 X; or L SC ; wherein 
{ TAIL ~ R4 } is H , CN , { HEAD ~ C1 C18 alkyl } , C1 C18 perfluoroalkyl , CH2 SO3 X ; or L SC ; wherein
TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH