Experimental investigations of a chiral smectic glass-forming liquid crystal

Experimental results are reported for a chiral smectic A (SmA*) liquid crystalline cholesteryl-carbonate, which suggest an unusual transition into a glassy state for a low molar mass mesogen. The glass transition is accomplished over a time period of several days at room temperature. It involves two processes, which are attributed to freezing of the mobility of the phenyl-containing flexible tails and subsequent glass formation of the bulky cholesteryl groups of the material. During the glass formation process no texture changes are observed and the qualitative electro-optical response is retained. This subtleness of the transition is also exemplified by only minute features in respective DSC curves. Deviations from the common electroclinic temperature dependence are observed below a temperature within the SmA* phase. During a second process at lower temperature, the electro-optical switching then diminishes and a strongly increasing viscosity is observed with time. © 2008 Taylor & Francis.