SACM - United States of America
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Item Restricted LIQUID CRYSTALS NUCLEI COEXISTING WITH AN ISOTROPIC PHASE(Kent State University, 2022-08) Alqarni, Ali; Lavrentovich, OlegThe morphology of finite-size condensed materials is influenced by surface tension. To reduce surface area, tiny droplets of water in the air have spherical shapes, but solid crystals have facetted shapes defined by the orientation dependency of surface tension. Bulk interactions are unimportant in these two examples because they are either too weak to overcome surface tension in the first case or too powerful to enable internal curvatures in the second case. In liquid crystal droplets, the bulk and surface energies are more closely balanced, resulting in a more diversified morphology of structures such as smectic "batonnets", nematic spindle-like tactoids, and even the possibility for droplet division . Liquid crystals are well-known examples of ordered materials whose nuclei emerge from an isotropic state and have a shape topologically equivalent to a sphere. In the first part of the thesis, we explore experimentally and theoretically the nuclei of columnar lyotropic chromonic liquid crystal coexisting with the isotropic phase that is toroidal in shape. We study the lyotropic chromonic liquid crystal (LCLC) composed by plank-like molecules of disodium chromoglycate (DSCG) with hydrophobic polyaromatic cores and hydrophilic peripheries. The goal is to establish the physical mechanisms in the balance of elasticity and anisotropic surface tension that produce toroidal shapes and establish how these shapes depend on parameters such as molecular concentrations and the presence of a crowding agents. The second part of the thesis will focus on the droplets of chiral and ferroelectric liquid crystal materials.24 0Item Restricted Solvation Dynamics of Choline Halide-Based Deep Eutectic Solvents(2023) Alfurayj, Ibrahim Ahmed; Burda, ClemensThe intermittent nature of renewable energy sources requires reliable and cheap long-term energy storage technologies. Redox flow batteries (RFBs) are reliable, scalable, and cost-efficient. Electrolytes are crucial for RFB's performance. Deep eutectic solvents (DESs) are a new class of ionic liquids with relatively cheap and easy synthesis. In addition, their properties are tunable, making DES an excellent candidate for many energy and industry applications. A DES mixture is created by combining hydrogen-bond acceptor (HBA) and donor (HBD) in a specified ratio, producing a mixture with a lower melting point than its constituent components. Varying the type and ratio of HBA results in tunning DES properties. Also, adding co-solvents, such as water, can provide further tunning to DES mixtures. This dissertation aims to study the potential of water addition, HBA choice, and the compositional variation to optimize the solvation dynamics and physicochemical properties of choline halide-based DESs. Besides the most famous Ethaline (choline chloride ChCl): ethylene glycol (EG), 1:2), we reported the first choline fluoride (ChF) and EG-based DES mixture preparation with 1:2 molar ratio. We studied physical properties upon water addition by conductivity, density, viscosity, and ET(30) polarity. NMR, FT-IR, and Raman spectroscopies were used to characterize their structures. Femtosecond transient-absorption spectroscopy (fs-TSA) and NMR-diffusometry were used to study solvation dynamics, providing a powerful tool for studying charge transport properties. Volumetric properties were used to study the effect of water in EthalineF/water and Ethaline/water mixtures. This work also investigated the eutectic enhancement of dynamics and charge transport in Ethaline. We provided excellent tools, such as using B30 as a probe molecule in time-resolved spectroscopy to study solvation dynamics and correlating DES-DES self-interactions to experimental conductivities. Also, proved that water (>1 wt.%) can accelerate charge transport and enhance physical properties. The vibrational spectroscopies indicate that EthalineF has stronger hydrogen bond interactions than Ethaline. In addition, we reported the effect of the solvodynamic radius on the observed lower conductivity in EthalineF compared to Ethaline. Furthermore, based on the NMR diffusion measurements, we assigned the two F-NMR peaks to be EG and choline associated fluorides.17 0Item Restricted Temperature Dependent Partition Coefficients of Cyclohexylamine and Ethanolamine Between Octanol and Water Phases.pdf.pdf(2023-05-13) Alhilal, Ahmed Atiah S; Liu, YongThis study has investigated temperature dependence of octanol/water partition coefficients of cyclohexylamine and ethanolamine in temperature ranges of 5 to 25°C for cyclohexylamine and 17.5 to 25°C for ethanolamine. Experiments are largely based on a method developed by a researcher at the University of South Florida, which can help reduce chemical waste, save effort and time, and generate more reliable results. The study has found that the partition coefficient of cyclohexylamine is higher than that of ethanolamine, consistent with literature results. This also indicates that our approach is probably valid. By investigating correlation between chemical descriptors and partition coefficients of more than 1500 amine chemicals theoretically, we have shown that cyclohexylamine has higher values for descriptors that are positively correlated with logP. In addition, it has been found that temperature influences the partition coefficient of ethanolamine more than that of cyclohexylamine, probably due to smaller molecule size of ethanolamine. The partition coefficient of cyclohexylamine has a seemingly inverse relationship with temperature. On the other hand, temperature dependence of ethanolamine is more complicated. Moreover, we have determined thermodynamics of partition process including enthalpy, entropy, and free energy. Overall, these findings could be used to better assess their potential risks to public health.33 0