NANOSCALE PATTERNING OF LIQUID CRYSTAL AQUEOUS INTERFACES

Date

2023-6-13

Author

Akman, Ali

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Assembled colloidal structures have gained significant interest in scientific and technological advances. We experimentally investigated the self-assembly of the colloids at fluidic interfaces that mediate elastic interactions. Whereas past studies have reported the assembly of the micrometer- or molecular-sized species at aqueous interfaces of liquid crystals (LCs), herein we study the assembly of the intermediate-sized nanoparticles. Specifically, the surface-modified silica nanoparticles (50 to 500 nm-sized) were adsorbed at LC-water interfaces (either nematic or cholesteric droplets with a range of configurations) and their positioning was investigated using electron microscopy after polymerization of the LCs. Experiments and modeling of the interparticle interactions revealed that the electric double-layer forces and the elastic forces caused by LC strain are dominant in the assembly and their contributions can be tuned to direct the self-assembly of the nanoparticles to maintain textures patterned by the sub-interface symmetry of confined cholesteric LCs. At high ionic strengths, we observed a strong localization at the defects, whereas intermediate ionic strengths resulted in a partial enrichment of the nanoparticles into cholesteric fingerprint patterns with interaction energy estimated as ≈3 kBT. This result was comparable with the calculations based on the strength of the binary interactions of the nanoparticles. The findings also support the role of ion partitioning at the LC-aqueous interfaces on the formation of the assemblies. The experimental findings on the formation of rich assemblies of nanoparticles with elastic interactions can be utilized for applications in sensors, microelectronics, and photonic devices.

Subject Keywords

Liquid Crystal, Cholesterics, Nanoparticle Assembly, Patterning, Elasticity

URI

https://hdl.handle.net/11511/104414

Collections

Graduate School of Natural and Applied Sciences, Thesis