CBE Doctoral Dissertation Defense: “Fabrication of Functional Nanostructured Polymers Based on Thermotropic and Lyotropic Liquid Crystals Derived from Sustainable Resources” (Ruiqi Dong)

Abstract:

Nanostructured materials with interconnected nanoscale structures have garnered significant attention due to the ability to precisely regulate molecular transport by tuning molecular-level properties and offering more functional interfaces for interactions compared to bulk systems. Through self-assembly, liquid crystal (LC) mesophases offer a route to achieve nanostructured polymers, a promising alternative to traditional nanostructured inorganic materials and block copolymers. LC mesophases can spontaneously form monodisperse nanostructures and their self-assembly can be precisely controlled to yield well-organized 1D, 2D, and 3D periodic nanostructured materials.

Developing functional polymers from sustainable resources is crucial due to the economic and environmental benefits that result. Sustainably derived unsaturated fatty acids are of interest in this regard because their unsaturated carbon bonds allow crosslinking to form stable polymers, and their carboxylic acid functional groups enable specific surface chemistry and chemical derivatization.

This presentation focuses on how useful nanostructured functional materials can be realized from thermotropic and lyotropic liquid crystals derived from unsaturated fatty acids, and on the properties of the materials thus produced. While prior use of the so-called “molecular templating” approach has produced well-defined nanostructured membranes from thermotropic LCs, precise tuning of pore size and functionality (e.g. for addressing different applications) remains a challenge. We developed a new approach in which changing the stoichiometry of building blocks of self-assembling supramolecular constructs led to a robust handle for controlling pore shape, and pore size with sub-nm resolution. The approach used thermotropic LCs based on citronellol, a plant-derived molecule. To balance selectivity and permeability, we developed highly selective and permeable thin nanofiltration membranes based on lyotropic LCs from conjugated linoleic acid. This reproducible process can be applied to various systems for creating larger-scale nanostructured thin films. Additionally, we explored LC materials for ion and electron transport, presenting for the first time a nanostructured lyotropic LC membrane for cation conduction derived from conjugated linoleic acid, which shows improved electron transport performance compared to single-ion polymeric electrolyte materials.