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Large single crystals, as nearly perfect as possible, are required for magnetic resonance studies of the solid state. A limited number of substances occur naturally in crystals of sufficient size or purity for this type of experiment. Most of the nuclear magnetic resonance work done to date on single crystals has been performed using naturally occurring crystals. Section I of this thesis describes methods used to grow suitable crystals artificially, thus extending the scope of the magnetic resonance experiments. The orthorhombic sodium dihydrogen orthophosphate dehydrate has been produced in large single crystals which were used subsequently in the study of the nuclear magnetic resonance absorption spectrum of Na-23 in this crystal. The spectrum was observed as the crystal was rotated about the three crystallographic axes which are mutually perpendicular for the orthorhombic case. A maximum of twelve lines were observed when neither of the crystallographic axes were perpendicular to the external magnetic field. The number of lines was reduced to six when one of the axes was made perpendicular to the field, while only three lines were observed when two crystallographic axes were made perpendicular to the external magnetic field. These observed numbers of lines were interpreted by assuming four Na-23 sites, possessing identical eigenvalues and differing only in their orientation. These four sites are related by three mutually perpendicular two-fold rotation axes, each of which must be parallel to one of the three crystallographic axes. This interpretation is in complete accord with the space group P222 assigned to NaH2PO42H2O from morphological data. The complete set of properties of the quadruple coupling tensor was determined at each of the Na-23 sites. The value of the quadruple coupling constant (eQ Φzz)/h where Q is the nuclear quadruple moment and Φzz is the largest principle value of the electric field gradient tensor is: 1179.0 ± 0.5 kc/sec. The value of the asymmetry parameter η defined as (Φxx – Φyy)/Φzz is: 0.466 ± 0.005. The table of the direction cosines of the principle axes of the electric field gradient tensor with respect to the crystallographic axes appear in Table VII. / Thesis / Master of Science (MSc)

No / Pure anhydrous polymorphs of carbamazepine were prepared by solution-enhanced dispersion with supercritical fluids (SEDSTM). Crystallization of the polymorphs was studied. Mechanisms are proposed that consider the thermodynamics of carbamazepine, supersaturation in the SEDSTM process, and the binary phase equilibria of organic solvents and the carbon dioxide antisolvent. -Carbamazepine was crystallized at high supersaturations and low temperatures, -carbamazepine crystallized from a methanol-carbon dioxide phase split, and -carbamazepine crystallized via nucleation at high temperatures and low supersaturation.

Zhou, Xuechang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 51-53). / Abstracts in English and Chinese. / Abstract --- p.i / 摘要 --- p.ii / Acknowledgement --- p.iii / Table of contents --- p.iv / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Protein crystallization --- p.1 / Chapter 1.1.1 --- The principle of protein crystallization --- p.3 / Chapter 1.1.2 --- Protein crystallization approaches --- p.4 / Chapter 1.1.3 --- Screening strategies and approaches --- p.6 / Chapter 1.2 --- Microfluidic systems for protein crystallization --- p.7 / Chapter 1.2.1 --- Integrated valve-controlled microfluidic system --- p.8 / Chapter 1.2.2 --- Droplet-based microfluidic system --- p.9 / Chapter 1.2.3 --- Objective of the research --- p.10 / Chapter 2 --- Nanoliter Liquid Dispensing Method --- p.12 / Chapter 2.1 --- Introduction --- p.12 / Chapter 2.2 --- Experimental --- p.14 / Chapter 2.2.1 --- The fabrication of SU-8 master --- p.14 / Chapter 2.2.2 --- The fabrication of PDMS microfluidic device --- p.16 / Chapter 2.2.3 --- The fabrication of glass and PMMA microwells --- p.17 / Chapter 2.2.4 --- The liquid dispensing into microwells --- p.17 / Chapter 2.3 --- Results and discussions --- p.20 / Chapter 2.3.1 --- The internal vacuum pumping source --- p.20 / Chapter 2.3.2 --- The efficiency of the pumping --- p.23 / Chapter 2.3.3 --- The removal of PDMS channel patch --- p.26 / Chapter 2.4 --- Conclusion --- p.29 / Chapter 3 --- The Screening of Protein Crystallization Conditions --- p.30 / Chapter 3.1 --- Introduction --- p.30 / Chapter 3.2 --- Experimental --- p.31 / Chapter 3.2.1 --- The design and fabrication of the screening chip --- p.31 / Chapter 3.2.2 --- The screening of protein crystallization conditions --- p.32 / Chapter 3.2.3 --- Crystallization and X-ray diffraction of an unknown protein --- p.33 / Chapter 3.3 --- Results and discussions --- p.33 / Chapter 3.3.1 --- Sparse matrix screening strategy in microwell arrays --- p.33 / Chapter 3.3.2 --- The results of the sparse matrix screening --- p.39 / Chapter 3.3.3 --- Crystal extraction and X-ray diffraction --- p.40 / Chapter 3.4 --- Conclusion --- p.41 / Chapter 4 --- Conclusion --- p.43 / Chapter 4.1 --- Summary --- p.43 / Chapter 4.2 --- Discussions and future directions --- p.44 / Appendix Information --- p.47 / References --- p.51

A thermodynamical framework is presented that describes the solidification of molten polymers to an amorphous as well as to a semicrystalline solid-like state. This framework fits into a general structure developed for materials undergoing a large class of entropy producing processes. The molten polymers are usually isotropic in nature and certain polymers crystallize, with the exception of largely atactic polymers, which solidify to an amorphous solid, to an anisotropic solid. The symmetry of the crystalline structures in the semicrystalline polymers is dependent upon the thermomechanical process to which the polymer is subjected to. The framework presented takes into account that the natural configurations associated with the polymer melt (associated with the breaking and reforming of the polymer network) and the solid evolve in addition to the evolving material symmetry associated with these natural configurations. The functional form of the various primitives such as how the material stores, dissipates energy and produces entropy are prescribed. Entropy may be produced by a variety of mechanisms such as conduction, dissipation, solidification, rearragement of crystalline structures due to annealing and so forth. The manner in which the natural configurations evolve is dictated by the maximization of the rate of dissipation. Similarly, the crystallization and glass transition kinetics may be obtained by maximization of their corresponding entropy productions. The restrictions placed by the second law of thermodynamics, frame indiference, material symmetry and incompressibility allows for a class of constitutive equations and the maximization of the rate of entropy production is invoked to select a constitutive equation from an allowable class of constitutive equations. Using such an unified thermodynamic approach, the popular crystallization equations such as Avrami equation and its various modifications such as Nakamura and Hillier and Price equations are obtained. The predictions of the model obtained using this framework are compared with the spinline data for amorphous and semicrystalline polymers.

Thesis (Ph. D.)--Brandeis University, 2010. / "UMI:3390521." MICROFILM COPY ALSO AVAILABLE IN THE UNIVERSITY ARCHIVES. Includes bibliographical references.

Nature provides fascinating examples of functional materials with hierarchical structures. Nano and microscale materials have been prepared by synthetic approaches via the self-assembly of discrete building blocks with the aim to mimic nature’s materials in complexity and size. The solution-state self-assembly of block copolymers (BCPs) with crystallizable core-forming blocks has enabled access to low curvature morphologies such as 1D and 2D micelles via a spontaneous nucleation method termed crystallization-driven self-assembly (CDSA). Via a seeded growth method known as living CDSA, 1D and 2D micelles of controlled dimensions and low dispersity can easily be prepared. However, due to the challenges associated with the synthesis of high aspect ratio nanoparticles and the low number of noncytotoxic polymers known to undergo CDSA, their use for biomedical applications has been limited. The aim of the work described in this thesis is to develop nanofibers of precise dimensions, with nontoxic materials, for potential biomedical applications such as drug delivery, tissue engineering and materials reinforcement. Chapter 1 describes how nature makes superb functional hierarchical materials that serve as inspiration for the development of synthetic methods for the preparation of nano and microstructures. The principles regarding the solution-state self-assembly of BCPs with amorphous or crystalline core-forming blocks are discussed. The preparation of length-controlled nanostructures, segmented micelles, and supermicelles via living CDSA and micelle self-assembly are presented. An introduction to nanoparticle drug delivery, materials reinforcement, and tissue engineering with emphasis on the development and advantages of high aspect ratio nanofibers is given. Finally, a brief perspective on the development of nanofiber-based therapeutics is provided. Chapter 2 discusses the preparation of coaxial-core core nanofibers from the self-assembly of triBCPs. The nanofiber structure is comprised of a crystalline inner core, an amorphous hydrophobic outer core, and a water-soluble corona-forming block. Encapsulation of a model hydrophobic molecule was achieved by the outer amorphous core. This represents the first example of water-soluble, length-controlled, and low length-dispersity (Ð) nanofibers loaded via non-covalent interactions. In Chapter 2, preliminary studies suggested cargo uptake by diBCP nanofibers may be possible. Chapter 3 focusses on investigating the non-covalent loading of length controlled diBCP nanofibers with a hydrophobic cargo. The effect of the chemical identity and the length of the corona-forming blocks was also studied. Chapter 4 describes the self-assembly of B-A-B triBCPs with crystallizable hydrophobic ‘B’ terminal segments to yield fiber-like micelle networks and their potential applications. Conditions for the preparation of discrete crystalline core flower-like micelles and intermicellar fiber-like networks of crystalline core nanofibers were investigated. For the first time, crystalline core nanofiber networks are reported. Chapter 5 focuses on the proof-of-concept development of water-soluble length-controlled nanofibers with corona-forming blocks capable of targeting specific cancer tissue. Additionally, segmented nanofibers for drug delivery applications were prepared. Finally, the association of curcumin with the nanofiber corona-forming block was briefly investigated. Chapter 6 summarizes the work presented in this thesis which contributes towards the development of length-tunable nanofibers for biomedical applications and outlines future research directions of the work presented. / Graduate / 2023-04-20

Crystallization is a key unit operation in the fine chemical and pharmaceutical industries, many of which employ batch stirred vessels for crystallization. Although using stirred vessels for crystallization has advantages such as better mixing and faster cooling, one of the disadvantages is that due to the presence of mechanical parts in the vessel such as baffles, impeller etc., crystals break up while stirring and generate unwanted secondary nucleation. This process contributes to a wide crystal size distribution with a smaller than desired mean crystal size. For studying crystal breakage phenomenon, experimentalists choose to use nonsolvents for crystal breakage experiments to isolate breakage from simultaneously occurring phenomena such as Ostwald-ripening, aging and agglomeration. Although performing experiments in non-solvents eliminates other phenomena and helps isolate breakage, the results can not always be correlated to saturated solutions due to density and viscosity differences between the two conditions. In this research, the effects of Ostwald ripening, aging and agglomeration on the crystal size and shape distributions are quantitatively measured. Micro and macro scale experiments were performed in both non-solvents and saturated solutions and the results were compared to determine the effects. Both in situ focused beam reflectance method (FBRM) and off-line analyses were performed to characterize the crystal size distributions. Results from experiments show that there is significant difference between the breakage behavior of crystals in non-solvents and in saturated solutions, mplying significant impacts of Ostwald ripening, aging, agglomeration and dissolution in saturated solutions. Calculations using Zwietering correlation also show that the difference between the viscosities and densities in the two systems may also be a contributing factor to the difference in the breakage profiles. It was also found that growth rates of crystals can differ when they are subjected to stress and strain. In macroscale experiments, dissolution was found to have a significant impact on the crystal size distribution. Abrasion was found to be the dominating fracture mechanism for most systems. Extent of breakage and morphological changes were found to be dependent on stirring rates, suspension density, shape and hardness of crystals and the type of system.

It was the objective of this research to develop high temperature and high performance polyimides that also display (a) thermal stability; (b) crystallinity in the initial material and ability to crystallize from the melt; (c) fast crystallization kinetics and (d) melt processability. This unique combination of properties is presently unavailable in any other polyimide. In this regard, the present work investigates the crystallization, morphology and thermal stability of two novel semicrystalline polyimides based on the same diamine, 1,3-bis (4-aminophenoxy) benzene (TPER), but two different dianhydrides, 3,3',4',4'-biphenyltetracarboxylic dianhydride (BPDA) and 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA). Phthalic anhydride was used as an endcapper to improve the thermal stability of the polyimides. The BPDA based polyimide was also tested extensively as a structural adhesive using Ti-6Al-4V coupons. Additionally, these polyimides are based on monomers, that are presently commercially available. The bulk thermal stability of the polyimides was first evaluated using dynamic and isothermal thermogravimetric experiments. DSC was utilized to test the ability of the polyimides to crystallize from the melt after exposures to varying melt times and temperatures. Exceptional thermal stability was demonstrated by BPDA based polyimide with no change in the melting behavior after 40 min at 430°C or 30 min at 440°C. The semicrystalline morphology of the material was studied using hot stage polarized optical microscopy (OM) and atomic force microscopy. The spherulitic growth rates were determined as a function of crystallization temperature after quenching from various melt times and temperatures. The effect of crystallization temperature, previous melt time and melt temperature on the morphology was considered. The spherulitic growth rates increased with increasing undercooling in the temperature range studied (nucleation controlled), while the growth rate at a specific crystallization temperature decreased on increasing the previous melt time and temperature. The melting behavior was studied after different crystallization times and temperatures and also as a function of different heating rates. Crystallization kinetics was followed both isothermally and non-isothermally using DSC and OM. Avrami analysis was performed for TPER-BPDA and the obtained results were correlated with microscopic observations. Melt viscosity measurements were carried out as a function of melt temperature, melt time and frequency. The adhesive investigations for TPER-BTDA utilized lap-shear test, wedge test and double cantilever beam tests. The durability of the adhesive and the fracture surface was studied after exposure to various solvents and after high aging and testing temperatures. The polyimide demonstrated very high average room temperature lap-shear strengths (8400 psi or 59 MPa), excellent solvent resistance and durability of strengths at high aging and testing temperatures. / Ph. D.