Two series of compounds with semifluorinated chains have been synthesized. These compounds were characterized by IR, H-1 NMR, F-19 NMR, MS, and elemental analysis. Their phase-transition, behavior was investigated by differential scanning calorimetry and polarizing optical microscopy. Both the introduction of a triple bond and the decrease of the polarity of the core act to decrease the clearing points and suppress the formation of smectic C phase.