Dielectric measurements of diblock semiluorinated n-alkanes, (F(CF2)(n)(CH2)(m)H), n=10, m=6-14, were carried out in the frequency range 20Hz to 10(6) Hz and in the temperature range from the waxy solid to isotropic state. Dielectric loss curves were observed only in the mesophase/liquid crystal state. The activation energies for the materials of m=6-9 were smaller than those of m=11 and 12. Single relaxation process can explain the observations in liquid crystalline phase. An alternation in the total integrated intensity, Delta epsilon’ in the vicinity of phase transition temperature was found against even/odd number of carbon in alkyl group.