Enhanced smectic polymorphism of a cholesteric side chain co-oligosiloxane by blending with small molecule liquid crystals

Abstract

We have shown recently that a side chain chiral industrial co-oligosiloxane exhibits an original blue phase behaviour at the cholesteric-isotropic transition [1–3]. This same material has been studied dissolved in various polar small molecule nematic or cholesteric liquid crystals and it was shown that these associations are responsible for a large induced smectic domain. These systems allow the adjustment of the smectic A-cholesteric transition temperature from 180°C to room temperature, depending on the nature and concentration of the associated small molecule liquid crystal. Moreover the kinetics of this transition is strongly slowed down at high co-oligomer concentrations, suggesting, as confirmed by a preliminary X-ray study on the pure material, that the presumed glass transition allowing for the quenching of the Bragg optical properties at room temperature is in fact strongly associated with strong smectic correlations between the mesogenic parts.