Reentrant Nematic Mixtures

Induced Smectic Phases I. Polymorphism in Binary Mixtures of Alkyloxybenzylidene-alkylanilines with Alkyl- and Alkyloxy- cyanobiphenyls

“…Besides the SA phase at medium concentra tions a second S \ phase, which is separated by a nematic miscibility gap, appears at high 8 OCBP concentrations in this system. Furthermore, a re entrant nematic behaviour is observed at high con centrations of 8 OCBP in accordance with earlier results [8].…”

“…X-ray measurements [3] have shown that according to the layer thickness the induced phases contain the unassociated cyanobiphenyls, whereas the pure cyanobiphenyls are known to form bilayers owing to association. However, the expected difference in the dependence of the layer thickness on concen tration for systems with interrupted and uninter rupted miscibility of the Sa phases could not be detected [8].…”

Binary systems of smectics A with enhanced nematic phase

“…To find the real cause responsible for the behaviour of certain pairs of compounds we compared the ratios of molecule lenghts (Table II) and the smectic layer spacings for all of the tested pairs of compounds. The disappearance of the smectic phase was observed in those mixtures (pairs [1][2][3][4][5][6][7][8][9] in which the ratio of molecule lengths 1/1' varies in the range 1.07-1.28, and the ratio of smectic layer spacings varies Hardouin et al [21] found, by X-ray scattering, two types of cybotactic groups in the re-entrant nematic phase of 4'-(octyloxybenzoyloxy)-4-cyanostilbene (T8). Some of those groups are characteristic of the high-temperature SAd phase and some of the low-temperature SA1 one.…”

“…In the afore mentioned systems, one of the compounds yields bimolecular smectic A layers (d > I) and the other compound yields monomolecular smectic A layers (d I). Their mixtures give an enhanced smectic with monomolecular layers [5] which joins in a continuous manner the smectic phase of the pure compound which has also a monomolecular layer.…”

“…· J. Physique 45 (1984) Domon and Billard [1], Engelen et al [2], Griffin et al [3]. An Oh [4] as well as the systems consisting of esters and Schiff's bases described by Engelen et al [5]. In the afore mentioned systems, one of the compounds yields bimolecular smectic A layers (d > I) and the other compound yields monomolecular smectic A layers (d I).…”