Kinetics of cold crystallization in two liquid crystalline fluorinated homologues exhibiting the vitrified smectic ${C_{A}}^{*}$ phase

Dielectric relaxation processes in the supercooled antiferroelectric smectic ${C_{A}}^{*}$ phase and crystallization kinetics of two chiral fluorinated 5HF6 and 6HF6 compounds from the same homologous series are investigated. Fragility parameters are determined from the relaxation time of the α-process, including $\tau_{HN}$ from the Havriliak-Negami formula and $\tau_{peak}$ denoting the position of the absorption peak. The coupling coefficient $\xi$ between the characteristic time of isothermal cold crystallization and relaxation time of the α-process is obtained. Despite similar values of the fragility index, the even 6HF6 homologue undergoes cold crystallization much faster than the odd 5HF6 homologue, with significantly different $\xi$ coefficients. Influence of the relaxation time of the $P_{H}$ process (anti-phase phason) in the smectic ${C_{A}}^{*}$ phase on the crystallization kinetics is presumed.