Local lamellar organisation of discotic mesogens carrying fluorinated tails

Abstract

A series of disc-shaped liquid crystals, monomers and dimers, have been investigated. A spacer linked to the pentakis(phenylethynyl)phenoxy core of the mesogens was substituted with perfluorinated chains to investigate the microphase segregating effect of such groups. The nematic phase, commonly found for these mesogens, is strongly stabilised by the presence of the fluorinated groups. X-Ray diffraction studies indicate clearly the onset of nanophase segregation in the nematic phase. Remarkable is the result, that the nanophase segregation directs the systems towards a lamellar organisation, rather than the columnar order that is commonly found for disc-shaped mesogens. This is also confirmed by the order in the underlying crystalline phase. X-Ray diffraction studies of the nematic phase show the characteristics of cybotactic smectic clustering, which has not been observed for discotic systems so far.