Phase behavior of solvent-nematogen mixtures

Area of Science:

• Physical Chemistry
• Materials Science
• Soft Matter Physics

Background:

• Liquid mixtures with nematogens exhibit coupled phase transitions, including fluid phase separation and isotropic-nematic ordering.
• This coupling leads to complex phase behavior distinct from simple mixtures or pure liquid crystals.

Purpose of the Study:

• To investigate the phase behavior of mixtures composed of a nematogen (5CB) and simple liquid solvents (squalane/squalene).
• To explore how tuning the solvent composition affects phase boundaries and reveals complex phase diagrams.

Main Methods:

• Experimental measurement of phase diagrams for binary and ternary mixtures.
• Systematic variation of solvent composition (squalene/squalane ratio).
• Application of a mean-field model integrating liquid mixing and nematic ordering theories.

Main Results:

• Observed two types of binary phase diagrams: one with and one without isotropic-isotropic coexistence.
• Identified a three-phase coexistence region by varying the squalene-to-squalane ratio.
• The mean-field model accurately predicted observed binary and ternary phase behaviors.

Conclusions:

• Coupled phase transitions in liquid mixtures can lead to complex, tunable phase diagrams.
• A simple mean-field model effectively describes the phase behavior of these multicomponent systems.
• The model provides a framework for predicting complex phase diagrams in systems with more components.