Abstract: Compounds of the formula (I) in which the symbols have the following meanings: R.sup.1 is straight-chain or branched (C.sub.3 -C.sub.2)alkenyl containing a terminal double bond, it being possible for one or two non-adjacent CH.sub.2 groups to be replaced by O and/or S atoms, A and B, independently of one another, are phenyl, diazine-2,5-diyl or diazine-3,6-diyl, with the proviso that one of the groups A or B is phenyl and the other is diazine, X is O or S, R.sup.2, R.sup.3 and R.sup.4, independently of one another, are H, straight-chain (C.sub.1 -C.sub.10)alkyl or branched (C.sub.3 -C.sub.10 )alkyl, R.sup.2, R.sup.3 and R.sup.4 not simultaneously being H, have the property of increasing the phase width in CC mixtures or depressing the melting point.

Abstract: A process for aligning a layer of a liquid-crystalline, polymeric material in which a gas or liquid stream is passed over the liquid-crystalline, polymeric material, preferably for aligning main-chain polymers which have a nematic phase by passing a hot stream of air onto the material. Electrooptical displays which contain an alignment layer of this type have high contrast. The alignment layers have advantages over conventional rubbed alignment layers since, for example, no electrostatic charging takes place.