. . . "???C, CO, O(CO)O, O, S, SO2, OCS, CH2 --O, CH2 --S, ##STR48## each L1 and L2 independently is a hydrogen, alkylene having up to 20 carbon atoms or CN Z is hydrogen, halogen, CN, --OR, COOR, NO2, halogen substituted or unsubstituted alkylene or alkenyl having up to 20 carbon atoms, a halogen substituted or unsubstituted oxyalkylene or oxyalkenyl having up to 20 carbon atoms, a halogen substituted o" .