Phase Transition in a Homologous Series of Cholesteryl α, α, ω-Trihydrofluoroalkylcarbonate (CTHFAC)

Abstract

Phase transitions in a homologous series of cholesteryl α, α, ω-trihydrofluoroalkylcarbonates [C₂₇H₄₅OC(O)OCH₂(CF₂)_pCF₂H, p = 1,3,5,7] (CTHFAC) were studied by differential scanning calorimetry, polarizing microscopy and dielectric method. The p = 5 and 7 compounds showed one cholesteric mesophase and two mesophases (cholesteric and smectic) monotropically on cooling, respectively, but the p=1 and 3 compounds had no mesophase. The dielectric data indicated the existence of one relaxation below 200 K in the polycrystalline state of all compounds. The mechanisms for the mesomorphisms and relaxations were discussed from the chemical structure.