Exploring “Dormant” Opto-Mechanical Properties of the Isotropic Phase of Liquid Crystals and Revealing Hidden Elasticity of (Ordinary) Liquids

• Main Authors: Laurence Noirez, Philipp Kahl
• Format: Article
• Language: English
• Published: MDPI AG 2018-06-01
• Series: Fluids
• Subjects: low- and high-molecular weight liquid crystals; flow birefringence; wetting; molecular liquids; low-frequency shear elasticity; solid-like properties
• Online Access: http://www.mdpi.com/2311-5521/3/2/43

There is little literature on the flow properties of the isotropic phase of liquid crystalline fluids. However, this phase is an ideal tool to bridge the physics of liquid crystals with those of (ordinary) fluids. Optical and mechanical studies are presented, demonstrating that away from any phase transition, the isotropic phase of liquid crystalline molecules (LCs) and liquid crystalline polymers (LCPs) can work as an optical oscillator in response to low-frequency mechanical excitation, establishing the elastic origin of the flow birefringence and “visualizing” the very existence of the elastic nature of the liquid state. Additionally, mimicking the excellent anchoring ability of liquid crystals, an alternative rheological protocol optimizing the fluid/substrate interfaces is presented to access the low-frequency shear elasticity in various one-component liquids and salt-free aqueous solutions.