Investigating Liquid Crystal Nano Droplets from a Molecular Perspective

Zeynep Sümer of University College London is to present her research as part of the Soft Matter Physics group seminar series via Microsoft Teams. Please find the link below.

Liquid Crystal (LC) droplets have been widely studied for variety of applications. Both theoretical and experimental studies have provided a profound understanding of physics and chemistry behind the LC droplet properties which enabled scientists to mature todays display technology. This understanding is also providing the foundation for many more exciting applications. Recent studies, e.g., show that orientation-shifting LC molecules could be adapted for biological detection or serve as a template for guiding the assembly of nanoparticles. [1, 2]

One question could be on the further intensification of the devices, which might require nano-sized LC droplets. It is difficult to identify the molecular behaviour in nano droplets with the current scale of widely used simulations and experimental setups. The results always enlighten the cumulative behaviour and neglect the individual molecules or small groups within these systems. Molecular simulations can probe system sizes down to nanometres and focus on interfaces, rather than a system of entire droplet; when the scale is larger, continuum mechanics calculations provide essential information, yet neglect the molecular identity of the materials.

In our recent studies, we focus on the molecular mesogen behaviour within a LC droplet. To be able to simulate these systems within a feasible computational cost, we preferred a coarsegrained simulation method called Dissipative Particle Dynamics (DPD). Starting from an interface of two dimensions, we further considered the interactions of surfactants and nanoparticles at the interface of LC droplet.[3 – 5] In an attempt to connect these molecular-level results with current and future applications, we then developed a computational framework that is able to connect molecular studies such as those just summarised to the larger scale typically encountered in current applications. The latter length scale is explored via the implementation of Qtensor calculations based on Landau – de Gennes theory. We acknowledge a productive collaboration with Prof. F. Anibal Fernandez which was instrumental for our meso-scale approach.

References:

[1] Dan, A., Aery, S., Zhang, S., Baker, D. L., Gleeson, H. F., & Sarkar, A. (2020). Protein Microgel-Stabilized Pickering Liquid Crystal Emulsions Undergo Analyte-Triggered Configurational Transition. Langmuir.

[2] Li, Y., Khuu, N., Prince, E., Alizadehgiashi, M., Galati, E., Lavrentovich, O. D., & Kumacheva, E. (2019). Nanoparticle-laden droplets of liquid crystals: Interactive morphogenesis and dynamic assembly. Science advances, 5(7), eaav1035.

[3] Sumer, Z., & Striolo, A. (2018). Manipulating molecular order in nematic liquid crystal capillary bridges via surfactant adsorption: guiding principles from dissipative particle dynamics simulations. Physical Chemistry Chemical Physics, 20(48), 30514-30524.

[4] Sumer, Z., & Striolo, A. (2019). Effects of droplet size and surfactants on anchoring in liquid crystal nanodroplets. Soft matter, 15(19), 3914-3922.

[5] Sumer, Z., & Striolo, A. (2020). Nanoparticles shape-specific emergent behaviour on liquid crystal droplets. Molecular Systems Design & Engineering, 5(2), 449-460.

Host: Professor Cliff Jones

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