Abstract: Compounds with the general formula (I): R—S1—A—Z1—B—S2—R, where A and B are independent ring systems with the formulae (a1), (a2) or (b), whereby in the trans-1,4-cyclohexylene ring, one or two non-adjacent CH2 groups may be replaced by oxygen, and whereby, in the 1,4-phenylene ring, one or two non-adjacent CH groups may be replaced by nitrogen; L1, L2, L3 represent, independently, hydrogen, C1-C20-alkyl, C1-C20-alkenyl, C1-C20-alkyloxy, C1-C20-alkyloxy carbonyl, formyl, C1C20-alkyl carbonyl, C1-C20-alkyl carbonyloxy, halogen, cyano or nitro; Z1, Z2, Z3 represent, independently, a single bond, —CH2CH2—, —CH2O—, —OCH2—, —COO—, —OOC—, —(CH2)4—, —O(CH2)3—, —(CH2)3O— or —C≡C—; S1, S2 represent a spacer unit; R represents crosslinkable groups, with the proviso that at least one of the ring systems A or B represents a ring system with the formula (a1