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arXiv · 2502.07037

Liquid crystalline structures formed by sphere-rod amphiphilic molecules in solvents

Nilanthi P. Haputhanthrige·Yifan Zhou·Jingfan Wei·Min Gao·Tianbo Liu·Oleg D. Lavrentovich
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Abstract

Self-assembly of amphiphilic molecules is an important phenomenon attracting a broad range of research. In this work, we study the self-assembly of KTOF4 sphere-rod amphiphilic molecules in mixed water-dioxane solvents. The molecules are of a T-shaped geometry, comprised of a hydrophilic spherical Keggin-type cluster attached by a flexible bridge to the center of a hydrophobic rod-like oligodialkylfluorene (OF), which consists of four OF units. Transmission electron microscopy (TEM) uncovers self-assembled spherical structures of KTOF4 in dilute solutions. These spheres are filled with smectic-like layers of KTOF4 separated by layers of the solution. There are two types of layer packings: (i) concentric spheres and (ii) flat layers. The concentric spheres form when the dioxane volume fraction in the solution is 35-50 vol%. The flat layers are formed when the dioxane volume fraction is either below (20 and 30 vol%.) or above (55 and 60 vol%.) the indicated range. The layered structures show no in-plane orientational order and thus resemble thermotropic smectic A liquid crystals and their lyotropic analogs. The layered packings reveal edge and screw dislocations. Evaporation of the solvent produces a bulk birefringent liquid crystal phase with textures resembling the ones of uniaxial nematic liquid crystals. These findings demonstrate that sphere-rod molecules produce a variety of self-assembled structures that are controlled by the solvent properties.

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Nilanthi P. Haputhanthrige, Yifan Zhou, Jingfan Wei, Min Gao, Tianbo Liu, Oleg D. Lavrentovich. 2025-02-10. Liquid crystalline structures formed by sphere-rod amphiphilic molecules in solvents. https://arxiv.org/abs/2502.07037

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