Microscopic models for nematic liquid crystals

Author(s)

Eduardo dos Santos Nascimento

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Física (IF/SBI)
• Defense date: 2018-02-28

Examining board members

Andre de Pinho Vieira; Luiz Roberto Evangelista; Cristiano Luis Pinto de Oliveira; Ítalo Marcos Nunes de Oliveira; Mario Jose de Oliveira

• Advisor: Andre de Pinho Vieira; Silvio Roberto de Azevedo Salinas

Abstract

We study, in a mean-field approximation, microscopic models which can lead to nematic liquid-crystalline phases. Considering attractive forces, we investigate models with quadrupolar interactions for intrinsically biaxial objects. These models present uniaxial and biaxial nematic mesophases, triple and multicritical points (tricritical point, Landau point, etc.). We also introduce a model for a binary mixture of intrinsically uniaxiail and biaxial objects, in an annealed treatment. The mixture exhibits phase diagrams with very rich topologies, where we find uniaxial and biaxial structures, reentrant phases and many different multicritical behaviors (tricritical point, critical endpoint, etc.). Moreover, assuming steric interactions, we investigate a density functional theory for hard anisotropic bodies at high densities, based on a van der Waals approximation. For hard spheroids, the model leads to an orientation space with forbidden regions for the particles. Also, the system phase separates in a nematic and an isotropic phases. (AU)

• FAPESP's process: 13/12873-9 - Microscopic models for nematic biaxial liquid crystals.
• Grantee: Eduardo dos Santos Nascimento
• Support Opportunities: Scholarships in Brazil - Doctorate