Stabilization and destabilization of the SA phase in mixtures of 4-nitrobenzyl-2,5-bis(4-n-alkyloxybenzoyloxy)benzoates

4-Nitrobenzyl-2,5-bis(4-n-alkyloxybenzoyloxy)benzoates exhibit S_A phases which are characterized by an antiparallel packing of the molecules and a partial intercalation of the terminal alkyl chains. In binary systems of selected rod-like components the S_A mixed phase can be stabilized or destabilized depending on the molecular length of the rod-like molecules. This unusual behaviour is mainly due to steric interaction and can be interpreted by a simple packing model.