Isothermal cold crystallization of antiferroelectric liquid crystal 3F5BFBiHex
Łukasz Kolek, Małgorzata Jasiurkowska-Delaporte, Ewa Juszyńska‐Gałązka, Tomasz Rozwadowski
Abstract
Isothermal cold crystallization of liquid crystalline substance of (2S)-octano-2-yl4′-(2-fluoro-4-{[5-(1,1,2,2,3,3,3heptafluoropropoxyy)pentylo]oxy}benzoyloxy)-[1,1′-biphenyl]-4-carboxylate (3F5BFBiHex) from antiferroelectric phase has been investigated by complementary method, i.e., differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS) and polarizing microscopy observations (POM). We employed the Avrami and Avramov approach to determine the dimensionality (n) and crystallization constant rate (k) parameters. The monitored crystal growth occurred to be two-dimensional. Two kinds of crystallization mechanisms were found depending on the temperature range. The kinetic factor dominated for the low-temperature range, while for higher temperatures the importance of the thermodynamic factor increased. The change in crystallization mechanisms was confirmed by the activation energy values, which for the high-temperature range was about 20 kJ/mol (DSC method) and about 30 kJ/mol (BDS method) higher than for the low-temperature range.