Anisotropic particles at liquid interfaces

Morgan, Scott Oliver

Abstract

In this thesis we study the adsorption dynamics and self-assembly of anisotropic particles at a liquid-liquid interface. Firstly, we couple a Langevin dynamics model with the high-resolution finite element analysis software package Surface Evolver, which explicitly includes interfacial deformations, to study the adsorption dynamics of ellipsoidal particles. Transient contact line pinning due to nanoscale defects on the particle surface are also included by renormalising particle friction coefficients and using dynamic contact angles relevant to the adsorption timescale. We reproduce the monotonic variation of particle orientation with time that is observed experimentally and are able to quantitatively model the adsorption dynamics for some experimental ellipsoidal systems but not others. However, even for the latter case, our model accurately captures the adsorption trajectory (i.e., particle orientation vs. height) of said particles.
Secondly, we extend our theoretical model to study cylindrical particles with the goal of using the adsorption kinetics of cylindrical nanorods at a liquid interface as a novel alternative route for assembling vertically aligned nanorod arrays. We find that the final orientation of non-neutrally wetting cylindrical nanorods is determined by their initial attack angle when they contact the liquid interface. Furthermore, the range of attack angles leading to the end-on state is maximised when nanorods approach the liquid interface from the bulk phase that is more energetically favorable.
Finally, we move from the role anisotropy plays in the adsorption process to investigating how particle anisotropy can be utilized to direct the self-assembly of particles adsorbed at a liquid-liquid interface. Specifically, by modeling undulating hexagonal-like platelets and changing the relative phase axis of the undulation’s peaks and the hexagonal particles vertices, we can direct the assembly to a number of different self-assembled ground states including hexagonal close packed, honeycomb and kagome lattices.

Citation

Morgan, S. O. (2022). Anisotropic particles at liquid interfaces. (Thesis). University of Hull. Retrieved from https://hull-repository.worktribe.com/output/4224664

• Thesis Type: Thesis
• Deposit Date: Jan 20, 2023
• Publicly Available Date: Feb 24, 2023
• Keywords: Physics
• Public URL: https://hull-repository.worktribe.com/output/4224664
• Additional Information: Department of Physics, The University of Hull
• Award Date: Apr 1, 2022