Binary Smectic Systems Including Trinuclear Pyrimidines with and without Nematic Gap

Abstract

Phase diagrams of binary mixtures are presented in which one component has been selected from among four trinuclear isomeric pyrimidines forming a nematic or smectic A, phase, and the second one from cyanocompounds forming an Ad smectic phase. Depending on the molecular structure of pyrimidine, mixtures were obtained that show or show not a nematic gap between the A1 and Ad smectic regions. In the latter case it was found that the relation TSA → N= f(x) has two independent branches in different ranges of the concentration x. The measured spacing of the smectic layers in such mixtures points to the possibility of the pyrimidine monolayer being transformed into a bilayer.