Investigation of de Vries SmA* mesophases in low molecular weight organosiloxane compounds

A series of novel low molecular weight organosiloxane compounds have been investigated using a number of techniques such as: texture, birefringence measurements and dielectric spectroscopy. Some materials under investigation are shown to have a direct transition to de Vries SmA* phase on cooling from the isotropic phase, whereas the others show first a transition from isotropic to orthogonal SmA*, followed by a transition from orthogonal SmA* to de Vries SmA* phase. We propose a phase diagram for a possible phase transition from SmA* to SmC* phase.