Lyotropic Liquid Crystals of Colloidal Gibbsite Nanoplatelets: Phase Transition, Kinetic Characterization, and Confinement Effect

Abstract

2D gibbsite nanoplatelets, [γ-Al(OH)₃], are widely used as an inorganic mineral platform for 2D lyotropic liquid crystal (LC) colloids. These particles are synthesized and enlarged using an improved hydrolysis method, resulting in highly crystalline (96.5%), low polydispersity (15.1%), and readily dispersible colloids in water. The aqueous mesomorphic system is characterized for the isotropic-to-nematic phase transition by analyzing number density and shear viscosity. Thermal stability is assessed through thermogravimetric analysis. Additionally, kinetic and thermodynamic parameters for 2D gibbsite nanoparticles are determined for the first time using three models (Coats-Redfern, Friedman, and Kissinger). In particular, the activation and Gibbs free energies for the first dehydration stage of gibbsite yield ranges of 98‒128 kJ mol⁻¹ and 135‒161 kJ mol⁻¹, respectively. To investigate the confinement effect of colloidal gibbsite-LCs, an isotropic gibbsite dispersion is introduced into a tube, leading to the uniform formation of gibbsite-LC layers along two distinct pathways: tangential to the liquid-air interface and as concentric circles along the tube walls. These findings offer valuable insights into potential applications, particularly in the domain of gas barrier inorganic films across various specialized fields.