Browsing by Author "Hutchins, Kristin M. (TTU)"
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Item Colossal Anisotropic Thermal Expansion in a Diazo-Functionalized Compound with Switchable Solid-State Behavior(2023) Ding, Xiaodan (TTU); Unruh, Daniel K. (TTU); Ma, Liulei (TTU); van Aalst, Evan J. (TTU); Reinheimer, Eric W.; Wylie, Benjamin J. (TTU); Hutchins, Kristin M. (TTU)Achieving substantial anisotropic thermal expansion (TE) in solid-state materials is challenging as most materials undergo volumetric expansion upon heating. Here, we describe colossal, anisotropic TE in crystals of an organic compound functionalized with two azo groups. Interestingly, the material exhibits distinct and switchable TE behaviors within different temperature regions. At high temperature, two-dimensional, area zero TE and colossal, positive linear TE (α=211 MK−1) are attained due to dynamic motion, while at low temperature, moderate positive TE occurs in all directions. Investigation of the solid-state motion showed the change in enthalpy and entropy are quite different in the two temperature regions and solid-state NMR experiments support motion in the solid. Cycling experiments demonstrate that the solid-state motions and TE behaviors are completely reversible. These results reveal strategies for designing significant anisotropic and switchable behaviors in solid-state materials.Item Controlling thermal expansion within mixed cocrystals by tuning molecular motion capability(2020) Ding, Xiaodan (TTU); Unruh, Daniel K. (TTU); Groeneman, Ryan H.; Hutchins, Kristin M. (TTU)Controlling thermal expansion (TE) behaviors of organic materials is challenging because several mechanisms can govern TE, such as noncovalent interaction strength and structural motions. Here, we report the first demonstration of tuning TE within organic solids by using a mixed cocrystal approach. The mixed cocrystals contain three unique molecules, two of which are present in variable ratios. These two molecules either lack or exhibit the ability to undergo molecular motion in the solid state. Incorporation of higher ratios of motion-capable molecules results in larger, positive TE along the motion direction. Addition of a motion-incapable molecule affords solids that undergo less TE. Fine-tuned TE behavior was attained by systematically controlling the ratio of motion-capable and -incapable molecules in each solid.Item Controlling thermal expansion within mixed cocrystals by tuning molecular motion capability(2020) Ding, Xiaodan (TTU); Unruh, Daniel K. (TTU); Groeneman, Ryan H.; Hutchins, Kristin M. (TTU)Controlling thermal expansion (TE) behaviors of organic materials is challenging because several mechanisms can govern TE, such as noncovalent interaction strength and structural motions. Here, we report the first demonstration of tuning TE within organic solids by using a mixed cocrystal approach. The mixed cocrystals contain three unique molecules, two of which are present in variable ratios. These two molecules either lack or exhibit the ability to undergo molecular motion in the solid state. Incorporation of higher ratios of motion-capable molecules results in larger, positive TE along the motion direction. Addition of a motion-incapable molecule affords solids that undergo less TE. Fine-tuned TE behavior was attained by systematically controlling the ratio of motion-capable and-incapable molecules in each solid.Item Differences in thermal expansion and motion ability for herringbone and face-to-face π-stacked solids(2022) Ding, Xiaodan (TTU); Zahid, Ethan (TTU); Unruh, Daniel K. (TTU); Hutchins, Kristin M. (TTU)A series of aromatic organic molecules functionalized with different halogen atoms (I/ Br), motion-capable groups (olefin, azo or imine) and molecular length were designed and synthesized. The molecules self-assemble in the solid state through halogen bonding and exhibit molecular packing sustained by either herringbone or face-to-face π-stacking, two common motifs in organic semiconductor molecules. Interestingly, dynamic pedal motion is only achieved in solids with herringbone packing. On average, solids with herringbone packing exhibit larger thermal expansion within the halogen-bonded sheets due to motion occurrence and molecular twisting, whereas molecules with face-to-face π-stacking do not undergo motion or twisting. Thermal expansion along the π-stacked direction is surprisingly similar, but slightly larger for the face-to-face π-stacked solids due to larger changes in π-stacking distances with temperature changes. The results speak to the importance of crystal packing and intermolecular interaction strength when designing aromatic-based solids for organic electronics applications.Item Removal of the Micropollutants Propranolol Hydrochloride and 2-Naphthol From Water by Pyridine-Functionalized Polymers(2022) Zheng, Qixuan (TTU); Unruh, Daniel K. (TTU); Hutchins, Kristin M. (TTU)The number and concentration of micropollutants in aqueous environments are increasing. Two such micropollutants include the pharmaceutical, propranolol hydrochloride, and dye intermediate, 2-naphthol. Here, we describe the synthesis of both linear and crosslinked pyridine-functionalized copolymers that bind and remove propranolol hydrochloride and 2-naphthol from water solutions. Propranolol hydrochloride and 2-naphthol both contain hydrogen-bond-donor groups, and the pyridine moiety on the polymer acts as a hydrogen-bond acceptor to facilitate removal. Copolymers with different amounts of pyridine comonomer are synthesized, and as the amount of the pyridine comonomer is increased, the ability of the polymer to bind and remove the contaminant also increases. The concentrations of propranolol hydrochloride and 2-naphthol decreased by approximately 20–40% and 60–88%, respectively, depending on the polymer type that is used in the binding experiment. A control polymer was synthesized by using styrene in place of the pyridine monomer. In analogous binding experiments, the styrene polymer decreases the concentration of propranolol hydrochloride by 2% and 2-naphthol by 26%. Thus, the binding effectiveness is significantly reduced when the hydrogen-bond-acceptor group is not present on the polymer. We also show that the best performing crosslinked pyridine-functionalized polymer is reusable. Overall, these polymer adsorbents demonstrate the potential for removal of micropollutants from water.Item Reversible interconversion of pharmaceutical salt polymorphs facilitated by mechanical methods(2023) Ma, Liulei (TTU); Zheng, Qixuan (TTU); Unruh, Daniel K. (TTU); Hutchins, Kristin M. (TTU)Salification of the drug trimethoprim with enantiopure D- or L-lactic acid afforded salts with up to five times improved solubility. Both salts are polymorphic and we demonstrate fully reversible interconversion (cycling) between the drug polymorphs using mechanochemistry and slurry methods. We show drug polymorph interconversion requires both solvent contact and mechanical force, revealing strategies for cycling between solid material forms.