Study of Interfacial Properties in Liquid Crystals Using Molecular Dynamics Simulations

Abstract

In this thesis, the nucleation phenomenon in a thermotropic liquid crystalline system is investigated using the molecular dynamics simulations technique. The interaction between liquid crystalline (LC) particles is modeled by using the Gay-Berne (GB) potential model. To understand the nucleation or interfacial phenomenon in GB LCs, the interfacial stiffness of the nematic-smecticB (nm-smB) interface in an unconfined and the interfacial tension of the wall-isotropic fluid (wall-iso) interface in a confined GB LC system are calculated.

For the unconfined GB system, we have mainly focused on analyzing the interfacial phenomenon with nematic (nm) and smectic-B (smB) phases due to inadequate studies on the nm-smB interface in the literature. The interfacial stiffness of the nm-smB interface is calculated using capillary wave theory. The identification of nm and smB phases separated by a planar interface is done by using a particle-based local bond order parameter. In addition, the morphology of homogeneous nm and smB droplets formed within the nm-smB coexistence is also analyzed. To identify the coexisting nm and smB phases separated by planar and non-planar interfaces, we have developed a local-averaging technique based on the orientational order parameter. This identification criterion helped us to determine the aspherical, cylindrical, and planar shapes of nm and smB droplets formed in the system.

In a confined system, the GB isotropic fluid is confined by soft, smooth, and repulsive walls. The interaction between GB particles and walls is defined by the Weeks-Chandler-Anderson (WCA) potential model. The interfacial tension of the interface between GB isotropic fluid and WCA wall (wall-iso interface) is determined using the pressure tensor method. The effect of the wall-particle interaction strength on the wall-iso interfacial tension is analyzed. Moreover, the finite-size effects on the interfacial phenomenon in confined and unconfined systems are also studied.