SELF-ASSEMBLY OF LIQUID CRYSTALS AND CHIRAL SUPERSTRUCTURES: FROM COARSE-GRAINED TO FULLY ATOMISTIC MODELS

Computer simulations have been used to study the self-assembly of liquid crystals and/or chiral superstructures in both coarse-grained and fully atomistic models. In chapters 4-6, coarse-grained models of rigid achiral bent-core and linear molecules were found to self-assemble to chiral superstructures and liquid crystalline phases. Chiral superstructures were calculated to be minima of the potential energy surface using energy minimization and Monte Carlo parallel tempering simulations. Chiral dopants were found to induce the system to adopt a consistent chiral twist direction, the first molecular scale computer simulation of this effect. Superstructural chirality can be tuned into rigid linear particles by the appropriate spacing of Lennard-Jones (LJ) particles. These results point to design rules that can be manipulated for the experimental synthesis of chiral structures from achiral particles.In chapters 7-8, the largest liquid crystal atomistic simulations to date, to our knowledge,have been performed for both a series of single component liquid crystals and liquid crystalmixtures. It was also demonstrated for the first time, to our knowledge, the formation of smectic phases from an isotropic liquid state at the all atom level. These simulations are in good agreement with experiments,[1, 2] and show that atomistic simulations are capable of capturing macroscopic phase behavior changes induced by a small variation in the structure of single component liquid crystal molecules, or by concentration change in the liquid crystal mixtures. This opens up the possibility of theoretically designing and screening liquid crystals with desired properties

Understanding the effect of side groups in ionic liquids on carbon-capture properties: a combined experimental and theoretical effort

Ionic liquids are an emerging class of materials with applications in a variety of fields. Steady progress has been made in the creation of ionic liquids tailored to specific applications. However, the understanding of the underlying structure-property relationships has been slower to develop. As a step in the effort to alleviate this deficiency, the influence of side groups on ionic liquid properties has been studied through an integrated approach utilizing synthesis, experimental determination of properties, and simulation techniques. To achieve this goal, a classical force field in the framework of OPLS/Amber force fields has been developed to predict ionic liquid properties accurately. Cu(i)-catalyzed click chemistry was employed to synthesize triazolium-based ionic liquids with diverse side groups. Values of densities were predicted within 3% of experimental values, whereas self-diffusion coefficients were underestimated by about an order of magnitude though the trends were in excellent agreement, the activation energy calculated in simulation correlates well with experimental values. The predicted Henry coefficient for CO2 solubility reproduced the experimentally observed trends. This study highlights the importance of integrating experimental and computational approaches in property prediction and materials development, which is not only useful in the development of ionic liquids for CO2 capture but has application in many technological fields

Infrared Spectroscopy of Li⁺ Solvation in Diglyme: Ab Initio Molecular Dynamics and Experiment

Infrared (IR) spectra of solutions of the lithium salt LiBF4 in diglyme, CH3O(CH2CH2O)2CH3, are studied via IR spectroscopy and ab initio molecular dynamics (AIMD) simulations. Experiments show that the major effects of LiBF4, compared to neat diglyme, are the appearance of a new broad band in the 250–500 cm–1 frequency region and a broadening and intensity enhancement of the diglyme band in the 900–1150 cm–1 region accompanied by a red-shift. Computational analysis indicates that hindered translational motions of Li+ in its solvation cage are mainly responsible for the new far-IR band, while the changes in the mid-IR are due to Li+-coordination-dependent B–F stretching vibrations of BF4– anions coupled with diglyme vibrations. Molecular motions in these and lower frequency regions are generally correlated, revealing the collective nature of the vibrational dynamics, which involve multiple ions/molecules. Herein, a detailed analysis of these features via AIMD simulations of the spectrum and its components, combined with analysis of the generalized normal modes of the solution components, is presented. Other minor spectral changes as well as diglyme conformational changes induced by the lithium salt are also discussed

Microstructure and Wear Resistance of TiCp/Ti6Al4V Composite Coatings by Follow-Up Ultrasonic-Assisted Laser Additive Manufacturing

With the increasing demand for the high agility and fast response of high-level equipment in the aerospace and energy power fields, it is increasingly urgent to improve the performance of the high-temperature and wear resistance of the corresponding high-level components. Ceramic-reinforced titanium matrix composites have excellent high-temperature and wear resistance, but, in laser additive manufacturing, the primary ceramic phase is coarse, and the morphology of the ceramic phase is difficult to control, which limits their further development. In this investigation, a follow-up ultrasonic-assisted laser-additive-manufacturing method was proposed to prepare a 30 wt.% TiC/Ti6Al4V composite coating on a Ti6Al4V surface. Under the effects of ultrasonic cavitation and acoustic streaming, the content of the unmelted TiC was reduced, the dendritic primary TiC in the solidification process was broken and the distribution uniformity of the primary TiC was improved. The content of the unmelted TiC in the composite coating decreased significantly under ultrasonic action, and it was only 50.23% of that without ultrasonic action. At the same time, the average size of the dendritic primary TiC in the composite coating decreased from 61.59 μm to 27.04 μm, which was 56.10% smaller than that without ultrasonic action. The average microhardness of the composite coating reached the maximum of 656.70 HV0.2 under ultrasonic power, and it was 83.21% higher than that of the Ti6Al4V substrate, and 26.44% higher than that of the composite coating without ultrasonic power. Due to the ultrasonic-cavitation and acoustic-streaming effects, the content of the unmelted TiC obviously decreased, so that the average friction coefficient of the composite coating increased, and the wear mechanism changed from abrasive wear to adhesive wear

Effects of TiO2 Doping on Microstructure and Properties of Directed Laser Deposition Alumina/Aluminum Titanate Composites

10.1080/17452759.2019.1622987Virtual and Physical Prototyping144371-38

Mapping of Functional Groups in Metal-Organic Frameworks

We determined the heterogeneous mesoscale spatial apportionment of functional groups in a series of multivariate metal-organic frameworks (MTV-MOF-5) containing BDC (1,4-benzenedicarboxylate) linkers with different functional groups--B (BDC-NH2), E (BDC-NO2), F [(BDC-(CH3)2], H [BDC-(OC3H5)2], and I [BDC-(OC7H7)2]--using solid-state nuclear magnetic resonance measurements combined with molecular simulations. Our analysis reveals that these methods discern between random (EF), alternating (EI and EHI), and various cluster (BF) forms of functional group apportionments. This combined synthetic, characterization, and computational approach predicts the adsorptive properties of crystalline MTV-MOF systems. This methodology, developed in the context of ordered frameworks, is a first step in resolving the more general problem of spatial disorder in other ordered materials, including mesoporous materials, functionalized polymers, and defect distributions within crystalline solids

Coloclyster of Red Peony Root Granules Alleviates Moderately Severe Acute Pancreatitis: A Double-Blinded, Placebo-Controlled, Randomized Clinical Trial

The red peony root derived from Paeonia lactiflora has been applied to treat human inflammatory diseases. To investigate its therapeutic potential in treating moderately severe acute pancreatitis (MSAP), which has been rarely studied, this study was designed as a double-blinded, placebo-controlled, randomized clinical trial. A total of 60 MSAP patients were enrolled and randomly divided into an experimental (n = 30) group and a control group (n = 30), who received a coloclyster of 15 g of red peony root or placebo granules dissolved in 150 mL of water, respectively. The patients’ demographic and clinical characteristics were recorded. The results showed that the experimental group had a shorter remission time of fever (p<0.05) and abdominal pain (p<0.01) and faster resumption of self-defecation (p<0.01) than did the control group. In addition, the coloclyster of red peony root decreased the modified Balthazar CT score as well as the serum interleukin-6 and tumor necrosis factor-alpha levels to a greater extent than did the placebo coloclyster (p<0.05). The remission times for the normalization of white blood cells and percentage of neutrophils and lymphocytes in the experimental group were also significantly shorter than those in the control group (p<0.05). In conclusion, a coloclyster of red peony root could help alleviate the clinical symptoms and shorten the course of MSAP by possibly attenuating systematic inflammation. This trial is registered with 14004664

Mapping of functional groups in metal-organic frameworks.

We determined the heterogeneous mesoscale spatial apportionment of functional groups in a series of multivariate metal-organic frameworks (MTV-MOF-5) containing BDC (1,4-benzenedicarboxylate) linkers with different functional groups--B (BDC-NH2), E (BDC-NO2), F [(BDC-(CH3)2], H [BDC-(OC3H5)2], and I [BDC-(OC7H7)2]--using solid-state nuclear magnetic resonance measurements combined with molecular simulations. Our analysis reveals that these methods discern between random (EF), alternating (EI and EHI), and various cluster (BF) forms of functional group apportionments. This combined synthetic, characterization, and computational approach predicts the adsorptive properties of crystalline MTV-MOF systems. This methodology, developed in the context of ordered frameworks, is a first step in resolving the more general problem of spatial disorder in other ordered materials, including mesoporous materials, functionalized polymers, and defect distributions within crystalline solids