Nucleation from Supercooled Liquid Crystal and Crystallization Reveled by the Fast Scanning Calorimeter

Homogenous nuclei free liquid crystal glass of 4-cyano-4'-octyloxy biphenyl-carbonitrile (8OCB) was obtained by fast cooling with a rate of 20000 K/s. The glass was then heated rapidly (20000 K/s) from far below the $T_{g}$ to a temperature near its $T_{g}$ and hold for varied time $t_{a}$. After that, the sample was once again quenched below its $T_{g}$. Finally, the sample was heated again to isotropic melt. We use evolution of the cold crystallization peak $h_{cc}$ with the holding time during the last heating scan to investigate the nucleation and crystallization processes occurring in the holding process. The $h_{cc}$ was found to increase at short $t_{a}$, indicating the increased number of nuclei; and decrease in the longer $t_{a}$, indicating the superposition of crystallization over the nucleation. Such technique shows potential for the study of nucleation kinetics in the condensed supercooled liquids.