# Crystallization Kinetics of an Equimolar Liquid Crystalline Mixture and Its Components
## 1 Introduction  
Smectic liquid crystals (Sm LCs), possessing a lamellar order, can show switching in the electric field if particular conditions are fulfilled: the molecules are chiral, the tilted smectic phase is present (SmC\({}^{\star}\) or its sub-phases), the component of the molecular dipole moment is non-zero in a direction perpendicular to the plane of tilt, and the helical twist of the molecular tilt along the layer normal is removed [1, 2]. Smectogenic compounds with such properties can be used in LC displays [3]. To control the temperature range of the tilted smectic phase, which defines the operating conditions of the display, numerous mixtures have been investigated, e.g., as described in [4, 5, 6, 7, 8, 9, 10, 11, 12]. The sequence of chiral smectic phases upon cooling is as follows: SmA\({}^{\star}\)\(\rightarrow\)SmC\({}_{\alpha}\)\({}^{\star}\)\(\rightarrow\)SmC\({}^{\star}\)\(\rightarrow\)SmC\({}_{\rm{F}2}\)\({}^{\star}\)\(\rightarrow\)SmC\({}_{\rm{F}1}\)\({}^{\star}\)\(\rightarrow\)SmC\({}_{\rm{A}}\)\({}^{\star}\), although particular LC compounds do not always exhibit all the smectic phases among these [13, 14, 15]. In the SmA\({}^{\star}\) phase, the average tilt angle of the molecules equals zero, while in SmC\({}^{\star}\) and its variations, the average tilt angle is larger than zero. The SmC\({}_{\alpha}\)\({}^{\star}\) phase is characterized by a helical order with a very short pitch, equal to a few smectic layer spacings. The SmC\({}^{\star}\) phase has a synclinic order of the molecular tilt, and shows ferroelectric properties--bistable switching in the electric field--in the bookshelf surface-stabilized geometry. The SmC\({}_{\rm{F}2}\)\({}^{\star}\) and SmC\({}_{\rm{F}1}\)\({}^{\star}\) phases are characterized by a twist of the tilt angle with a period of four and three smecticlayers, respectively. Finally, the SmC\({}_{\text{A}}\)* phase has an anticlinic order of the molecular tilt in the neighboring layers, and shows antiferroelectric properties--trisable switching in the electric field--in the bookshelf surface-stabilized geometry [2; 15; 16]. For practical purposes, the LC should not crystallize in the temperature range within which the display or another LC-based device operates. The formulation of mixtures enables lowering of the melting point compared to the pure compounds [4; 11; 12]. It is also beneficial to use glass-forming compounds/mixtures, which can stay in the metastable LC state, below the melting point, for a long time. The crystallization process consists of two stages: nucleation followed by crystal growth. If the temperature range optimal for nucleation is lower than the temperature range for crystal growth, and these ranges do not overlap or overlap poorly, then the crystallization upon cooling (melt crystallization) is hindered. In such case, the formation of the crystal phase occurs upon heating (cold crystallization) if the sample is cooled down previously to the temperature range where the stable nuclei are formed [17; 18; 19]. LC glasses with helical order are considered as materials for optical filters [20; 21]. Materials which show glass transition and cold crystallization are also proposed for application in energy storage [22; 23]. The most convenient materials are those which undergo glass transition at moderate cooling rates of -20 K/min or lower [19]. The 4-[(1-methylheptyloxy)carbonyl]phenyl 4\({}^{\prime}\)-octyloxy-4-biphenylclarboxylate compound, abbreviated as MHPOBC (Figure 1), was the first LC in which tristable switching in the electric field was detected, indicating the existence of the antiferroelectric smectic \({\text{C}}_{\text{A}}\)* phase (SmC\({}_{\text{A}}\)*) [16]. MHPOBC has been tested as a component of mixtures with other LCs [5; 6; 7; 8] and as a nanoparticle matrix in composites [24; 25; 26; 27; 28].