Influence of sample measuring cell on isothermal crystallization of liquid crystalline compound forming the smectic C-A* phase

Crystallization of liquid crystalline (S)-4'-(1-methylheptyloxycarbonyl) biphenyl-4-yl 4-[7-(2,2,3,3,4,4,4-heptafluorobutoxy) heptyl-1-oxy]-2,3-difluorobenzoate in isothermal conditions is investigated by polarizing optical microscopy and differential scanning calorimetry. It is shown that the sample container influences the crystallization kinetics, as a faster development of the crystal phase is observed on microscopic textures, for a sample in an electro-optic cell with a planarly aligning polymer layer, than for a sample in an aluminum pan used in a differential scanning calorimetry experiment. However, in both cases the total time of melt crystallization in the 291-303 K range is shorter than 10 min. Only at the highest investigated temperature, 305 K, the crystallization process is completed after 1.4 h because of a long initialization time. The difference with the glassforming (S)-4'-(1-methylheptyloxycarbonyl) biphenyl-4-yl 4-[7-(2,2,3,3,4,4,4-heptafluorobutoxy) heptyl-1-oxy]-2-fluorobenzoate is explained based on the thermodynamic driving force of crystallization.