Crystallization kinetics of equimolar liquid crystalline mixture and its components

TL;DR

This study investigates the crystallization behavior and phase transitions of a new equimolar liquid crystalline mixture and compares it with its pure components, revealing partial crystallization and vitrification phenomena.

Contribution

It provides detailed kinetic analysis of crystallization in the mixture using differential scanning calorimetry and models, highlighting differences from pure components.

Findings

Partial crystallization and vitrification of the mixture during cooling.

Complete or near-complete crystallization of pure components.

Nucleation-controlled crystallization kinetics observed.

Abstract

The new equimolar mixture comprises liquid crystalline compounds MHPOBC and partially fluorinated 3F2HPhF6. The phase sequence of the mixture is determined by differential scanning calorimetry, polarizing optical microscopy, X-ray diffraction, and broadband dielectric spectroscopy. The enantiotropic smectic A*, C*, and CA* phases are observed for the mixture. Only partial crystallization of the mixture is observed during cooling at 2-40 K/min and the remaining smectic CA* phase undergoes vitrification. In contrast, the crystallization of the pure components is complete or almost complete for the same range of cooling rates. The kinetics of the non-isothermal and isothermal crystallization of the mixture and pure components are investigated by differential scanning calorimetry. The non-isothermal data are analyzed by the isoconversional method, while the isothermal data are analyzed using the Avrami model. Typically, the nucleation-controlled crystallization kinetics are observed.