Castaño Castellar, Shaskya

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    Study of the effect of surfactants on the stability and structure of liquid crystal emulsions stabilized with nanoparticles under static and dynamic conditions
    (2023-05-12) Castaño Castellar, Shaskya; Acevedo Rullán, Aldo; College of Engineering; Acevedo Vélez, Claribel; Córdova Figueroa, Ubaldo; Department of Chemical Engineering; Acuña Guzmán, Salvador
    Liquid crystal (LC) emulsions are promising candidates for the development of responsive soft materials and applications, such as sensors. The unique optical properties of the dispersed LC phase can be tuned to respond to physical, biological, or chemical stimuli, while suspended in a continuous phase that provides supports and withstands stresses. However, stabilizing LC emulsions to preserve their ordered structure remains a challenge. In this study, the use of ZnO nanoparticle-surfactant complexes of three commercial surfactants: anionic sodium dodecyl sulfate (SDS), nonionic Triton-X, and cationic dodecyltrimethylammonium bromide (DTAB) to improve the stability of 5CB LC emulsions in aqueous glycerin solutions was investigated under static and dynamic conditions. Improved stability for at least a month were obtained with 0.01 w/w% ZnO nanoparticles and 0.01 mM of SDS or Triton-X, and 5 and 10 v/v% LC 5CB, while no stable emulsions were obtained for DTAB. The inclusion of ZnO nanoparticles did not affect the structural configuration of the LC droplets, maintaining a bipolar orientation for both SDS and Triton-X. Interfacial tension and ζ potential showed that ZnO nanoparticles adsorbed better at the LC-water interface in the presence of surfactants, contributing to droplet stabilization and dispersion. Steady-state rheology showed that LC droplets were stable under shear stresses of ~ O (102) mPa. This study demonstrates the potential use of ZnO nanoparticles with SDS or Triton-X surfactants as an alternative for long term stabilization of LC emulsions. The exceptional physicochemical properties of ZnO nanoparticles may allow for the development of novel soft matter hybrid systems.