Incorporation of water molecules in the crystal structure of an organic compound has strong effects on its physical and chemical properties. Therefore, the study on stability of water-incorporated pharmaceutical compounds and mechanisms of hydration and dehydration is very important for the pharmaceutical industries. The main goals of the present research project were quantitative description of the crystallization and solid-state transformations of pseudopolymorphs of sodium naproxen in order to provide fundamental information concerning stability of the pseudopolymorphic forms. Furthermore, macroscopic phenomena of size reduction and anisotropic water-removal by dehydration were rationalized by microscopic aspects of crystal lattice structures. The heats of solution for each pseudopolymorph were estimated by fitting the solubility data with the vant Hoff equation, and their use was extended by the thermodynamic cycle developed in the present study. According to the thermodynamic cycle, for an enantiotropic system, a form with a lower degree of hydration always has the lower heat of solution than a form with a higher degree of hydration, implying that a form with a lower degree of hydration is more stable. The relative stabilities of the dihydrated, the monohydrated, and the anhydrous sodium naproxen at 0% relative humidity were investigated by dehydration of the dihydrated form and powder X-ray diffraction. The monohydrate is more stable than the dihydrate and the result was supported by isothermal TGA experiments. This research explained why powder-like crystals of the anhydrous sodium naproxen were produced by dehydration of hydrated forms. The surfaces of the dehydrated crystals displayed cracks aligned along the b-axis of the monohydrate. These cracks made the anhydrous crystals, which were produced from the monohydrated species, very brittle and, eventually, such crystals were disrupted into much smaller entities. In addition, the existence of water channels in the unit cells of the monohydrate facilitates the dehydration in a direction more rapidly, especially, along the b-axis of the monohydrate. Rapid removal of water in a specific direction caused anisotropic dehydration.

This research is focused on investigating the effect of carbon nanotubes on macroscale composite laminate properties, such as, interlaminar shear strength, interlaminar fracture toughness and electrical conductivity along with studying the micro and nano-scale interactions of carbon nanotubes with epoxy matrix via thermomechanical and electrical characterization of nanocomposites. First an introduction to the typical advanced composite laminates and multifunctional nanocomposites is provided followed by a literature review and a summary of recent status on the processing and the characterization work on nanocomposites and composite laminates. Experimental approach is presented for the development of processing techniques and appropriate characterization methods for carbon nanotubes reinforced epoxy resin based multi-functional nanocomposites and carbon fiber reinforced polymer composite laminates modified with carbon nanotubes. The proposed work section is divided into three sub-sections to describe the processing and the characterization of carbon nanotube reinforced epoxy matrix nanocomposites, woven-carbon fabric epoxy matrix composite laminates modified with selective placement of nanotubes and unidirectional carbon fiber epoxy matrix composite laminates modified with carbon nanotubes. Efforts are focused on comparing the effects of functionalized and unfunctionalized carbon nanotubes on the advanced composite laminates. Covalently functionalized carbon nanotubes are used for improved dispersion and fiber-matrix bonding characteristics and compared with unfunctionalized or pristine carbon nanotubes. The processing of woven carbon fabric reinforced epoxy matrix composite laminates is performed using a vacuum assisted resin transfer molding process with selective placement of carbon nanotubes using a spraying method. The uni-directional carbon fiber epoxy matrix pre-preg composites are processed using a hot press technique along with the spraying method for placement of nanotubes. These macroscale laminates are tested using short beam shear and double cantilever beam experiments for investigating the effect of nanotubes on the interlaminar shear stress and the interlaminar fracture toughness. Fractography is performed using optical microscopy and scanning electron microscopy to investigate the structure-property relationship. The micro and nano-scale interactions of carbon nanotubes and epoxy matrix are studied through the processing of unfunctionalized and functionalized single wall carbon nanotube reinforced epoxy matrix nanocomposites. The multifunctional nature of such nanocomposites is investigated through thermo-mechanical and electrical characterizations.

This dissertation work addresses two important aspects of nanotechnology - stable dispersion and self-assembly of colloidal nanostructures. Three distinctly different types of nano-scaled materials have been studied: 0-dimensional ZnO quantum dots (QDs), 1-dimensional carbon nanotubes (CNTs), and 2-dimensional alpha-zirconium phosphate (ZrP) nanoplatelets. Specifically, highly crystalline ZrP layered compounds with differences in diameters have been synthesized and fully exfoliated into monolayer platelets with uniform thickness, followed by their self-assembly into liquid crystalline structures, i.e., nematic and smectic. A novel colloidal approach to debundle and disperse CNTs has been developed by utilizing nanoplatelets to gather and concentrate sonication energy onto nanotube bundles. In such a fashion, CNTs are fully exfoliated into individual tubes through physical means to preserve their exceptional physical properties. Moreover, monodisperse ZnO QDs with high purity have been synthesized through a simple colloidal approach. Exfoliated ZrP nanoplatelets are used to tune the dispersion of ligand-free ZnO QDs from micron-sized aggregates to an individual QD level depending on the ratio between nanoplatelets and QDs. Dynamic analysis suggests that the dispersion mechanism mainly involves the change of QD dispersion free energy due to the presence of nanoplatelets, so that QDs can interact favorably with the surrounding media. In addition, the nanoplatelet-assisted dispersion approach has been utilized to disperse QDs and CNTs into polymeric matrices. Dispersion - property relationship in polymer nanocomposites has been systematically investigated with emphasis on optical properties for QDs and mechanical properties for CNTs.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第23023号 / 理博第4700号 / 新制||理||1674(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 島川 祐一, 教授 寺西 利治, 教授 長谷川 健 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

In this work we introduce the Voronoi fundamental zone octonion (VFZO) interpolation framework for grain boundary (GB) structure-property models and surrogates. The VFZO framework offers an advantage over other five degree-of-freedom (5DOF) based property interpolation methods because it is constructed as a point set in a Riemannian manifold. This means that directly computed Euclidean distances approximate the original octonion distance with significantly reduced computation runtime (∼7 CPU minutes vs. 153 CPU days for a 50000×50000 pairwise-distance matrix). This increased efficiency facilitates lower interpolation error through the use of significantly more input data. We demonstrate grain boundary energy (GBE) interpolation results for a non-smooth validation function and simulated bi-crystal datasets for Fe and Ni using four interpolation methods: barycentric interpolation, Gaussian process regression (GPR) or Kriging, inverse-distance weighting (IDW), and nearest neighbor (NN)interpolation. These are evaluated for 50000 random input GBs and 10000 random prediction GBs. The best performance was achieved with GPR, which resulted in a reduction of the root mean square error(RMSE) by 83.0% relative to RMSE of a constant, average model. Likewise, interpolation on a large, noisy, molecular statics (MS) Fe simulation dataset improves performance by 34.4 % compared to 21.2 %in prior work. Interpolation on a small, low-noise MS Ni simulation dataset is similar to interpolation results for the original octonion metric (57.6 % vs. 56.4 %). A vectorized, parallelized, MATLAB interpolation function (interp5DOF.m) and related routines are available in our VFZO repository (github.com/sgbaird-5dof/interp) which can be applied to any of the 32 crystallographic point groups1. The VFZO framework offers advantages for computing distances between GBs, estimating property values for arbitrary GBs, and modeling surrogates of computationally expensive 5DOF functions and simulations.

In this work we introduce the Voronoi fundamental zone octonion (VFZO) interpolation framework for grain boundary (GB) structure-property models and surrogates. The VFZO framework offers an advantage over other five degree-of-freedom (5DOF) based property interpolation methods because it is constructed as a point set in a Riemannian manifold. This means that directly computed Euclidean distances approximate the original octonion distance with significantly reduced computation runtime (∼7 CPU minutes vs. 153 CPU days for a 50000×50000 pairwise-distance matrix). This increased efficiency facilitates lower interpolation error through the use of significantly more input data. We demonstrate grain boundary energy (GBE) interpolation results for a non-smooth validation function and simulated bi-crystal datasets for Fe and Ni using four interpolation methods: barycentric interpolation, Gaussian process regression (GPR) or Kriging, inverse-distance weighting (IDW), and nearest neighbor (NN)interpolation. These are evaluated for 50000 random input GBs and 10000 random prediction GBs. The best performance was achieved with GPR, which resulted in a reduction of the root mean square error(RMSE) by 83.0% relative to RMSE of a constant, average model. Likewise, interpolation on a large, noisy, molecular statics (MS) Fe simulation dataset improves performance by 34.4 % compared to 21.2 %in prior work. Interpolation on a small, low-noise MS Ni simulation dataset is similar to interpolation results for the original octonion metric (57.6 % vs. 56.4 %). A vectorized, parallelized, MATLAB interpolation function (interp5DOF.m) and related routines are available in our VFZO repository (github.com/sgbaird-5dof/interp) which can be applied to any of the 32 crystallographic point groups1. The VFZO framework offers advantages for computing distances between GBs, estimating property values for arbitrary GBs, and modeling surrogates of computationally expensive 5DOF functions and simulations.

Polymers with intrinsic microporosity (PIMs) showed the potential to provide highly permeable and highly selective membranes for gas separation applications with the ability to fine-tune their properties for better performance. The concept of microporosity was extended to the polyimides by using kinked, contorted and stable structures to obtain high gas performance combined with excellent solution-processability, high thermal stability, and a unique platform for a wide range of possible modifications and tunability. Thus, studying the structure-property relationships is a critical key to develop advanced materials that can replace the commercially available membranes like cellulose acetate and Matrimid. Importantly, in the microporous polyimides (PIM-PIs) system, varying the type of the side chains appended to the diamines or dianhydrides impacts polymeric membrane properties, and in turn, gas separation performance. In this dissertation, we have examined the effect of ring substitutes, incorporated into novel polyimides backbones, on polymer properties and gas separation performance. The choice of side group can induce subtle changes in material properties and molecular interactions between the polymeric chains and affect the pore-size distribution, chain packing and yielding distinct combination between gas permeability and permselectivity. We have shown that the effect of tertiary amine groups, in polyimide structures, on the CO2 solubility is marginal but it can control the chain packing. However, introducing bromine groups on the polymer backbone can boost the O2 permeability and O2/N2 selectivity and perform better than the commercially available membranes. BCBr4-SBIDA demonstrated the same O2/N2 selectivity relative to cellulose acetate but approximately 10-fold higher gas permeability. Combining high selectivity with good permeability was achieved by a newly designed carboxyl-functionalized homopolymer (6FDA-TrMPD) with CO2 permeability of 144 barrer and CO2/CH4 selectivity of 45. The new W-shaped CANAL diamines, prepared by one-step synthesis, were used as microporosity generators in polyimides and revealed promising gas transport performance with the same selectivity relative to cellulose acetate by 23-fold higher permeability (CANAL-PI-3-MeNH2). Therefore, developing advanced polymers for membrane-based gas separation can be obtained by an ideal combination between kinked monomers, side chains, and stable materials.

The main theme of this research is to understand the structure-property evolution during crystallization of a semicrystalline thermoplastic polymer. A combination of techniques including rheology, small angle light scattering, differential scanning calorimetry and optical microscopy are applied to follow the mechanical and optical properties along with crystallinity and the morphology. Isothermal crystallization experiments on isotactic poly-1-butene at early stages of spherulite growth provide quantitative information about nucleation density, volume fraction of spherulites and their crystallinity, and the mechanism of connecting into a sample spanning structure. Optical microscopy near the fluid-to-solid transition suggests that the transition, as determined by time-resolved mechanical spectroscopy, is not caused by packing/jamming of spherulites but by the formation of a percolating network structure. The effect of strain, Weissenberg number (We) and specific mechanical work (w) on rate of crystallization (nucleation followed by growth) and on growth of anisotropy was studied for shear-induced crystallization of isotactic poly-1-butene. The samples were sheared for a finite strain at the beginning of the experiment and then crystallized without further flow (Janeschitz-Kriegl protocol). Strain requirements to attain steady state/ leveling off of the rate of crystallization were found to be much larger than the strain needed to achieve steady state of flow. The large strain and We >1 criteria were also observed for morphological transition from spherulitic growth to oriented growth. An apparatus for small angle light scattering (SALS) and light transmission measurements under shear was built and tested at the University of Massachusetts Amherst. As a new development, the polarization direction can be rotated by a liquid crystal polarization rotator (LCPR) with a short response time of 20 ms. The experiments were controlled and analyzed with a LabVIEWTM based code (LabVIEWTM 7.1) in real time. The SALS apparatus was custom built for ExxonMobil Research in Clinton NJ.

This study focuses on the evolving microstructure and its associated mechanical properties during each step of a seven step manufacturing process for 1010 steel tubing. For the microstructural analysis, we employed optical microscopy to quantify the ferrite grain size and pearlite grain size at each material step. To determine the mechanical properties, we used a Vickers hardness indenter and performed both tension and compression tests at varying strain rates and temperatures. Mechanical tests results indicate decreasing strength with increasing grain size, agreeing with the Hall-Petch relation and were used to correlate hardness and yield strength with grain size. Additionally, tensile and compression tests were performed at different strain rates to examine the effect of microstructural features on the mechanical properties of the steel tubing. Understanding the structure/property relationships of 1010 steel tubing during different processing conditions allows tubing to be manufactured more efficiently with desirable mechanical properties.

Gels are used in many applications ranging from bioengineering and pharmaceuticals to food technology and soft-robotics because of their tunable physical and mechanical properties. In many of these applications, the materials need to sustain large deformation. The microstructure of gels changes significantly at large strain values, causing a deviation in the stress responses from that at low strain. The desired mechanical responses of gels can be obtained by tuning their microstructure, therefore, the structure-property relationship for gels is required to be understood for their practical applications. This dissertation discusses two types of gels, one consists of chemical crosslinking and hydrophobic associations, and the other gel only consists of physical crosslinking. The microstructure of these two gel systems is investigated and related to their mechanical responses. The gel system with chemical and physical crosslinking mimics properties of biomaterials like resilin. Resilin is a protein-elastomer that enables biological species for power amplified activities by taking benefits of specific responses of hydrophilic and hydrophobic segments. Inspired by the microstructure and mechanical properties of resilin, a stretchable and resilient hydrogel was synthesized through a simple free radical polymerization technique. These gels retract from the stretched state to the original state with high speed over a short time, such behavior has not been frequently reported for synthetic hydrogels. This gel is also capable of performing a power-amplified activity like catapulting an object. In addition to retraction experiments, the mechanical properties of this gel were investigated in tensile and cyclic loading to determine their resilience. The hydrophobic polymer concentration affects the swelling behavior and mechanical responses such as stretchability and resilience. The second gel system considered here is a physically assembled ABA triblock copolymer dissolved in a B-selective solvent. Here, two different triblock copolymers with different concentrations were utilized. The real-time microstructural change was captured using a RheoSAXS setup with a high flux X-ray beam. The real-time microstructure of these gels subjected to temperature, varying oscillatory strain amplitude, and during relaxation after step strain was captured. This dissertation advances the understanding of the structure-property relationship of microstructurally complex gels towards their potential practical applications.