Kinetics of induced crystallization of the LC(1-x)Sil(x) system.
This study explores the kinetics of a new feature, called "induced crystallization (IC)", observed in an Aerosil dispersed octylcyanobiphenyl (8CB) liquid crystal system. Heating rate dependent experiments were performed using modulation differential scanning calorimetry (MDSC) at various heating ramp rates. In the presence of Aerosil nanoparticles, a well-defined exothermic peak was found as an additional feature on the heating scan before the melting transition, which was absent in the bulk 8CB; hence, we like to call it an "IC" as it is induced by Aerosil nanoparticles in the system. The system LC1-xSilx was prepared by mixing Aerosil nanoparticles in the bulk 8CB by the solvent dispersion method (SDM) where LC represents bulk 8CB and Sil represents Aerosil nanoparticles with x as the Aerosil fraction. The concentration of the Aerosil nanoparticles (x) varied from 0 to 0.2 g/cm3 in the bulk 8CB. The IC transition peak showed a temperature shift and change in the shape and size in the presence of Aerosil nanoparticles. In addition, this transition shifted significantly with different heating ramp rates following an Arrhenius behavior showing activated kinetics. The presence of Aerosil nanoparticles caused a significant increase in the enthalpy and decrease in the activation energy for the IC transition as the density of Aerosil nanoparticles increases and showed a saturation for the highest density of Aerosil nanoparticles. This behavior can be explained in terms of molecular disorder and surface molecular interaction induced by adding Aerosil nanoparticles into the bulk of 8CB liquid crystal.
Sharma
Dipti
D
Department of Physics, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, USA.
Iannacchione
Germano
G