Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1940. / MIT copy bound with: The use of a liquid model in studying the characteristics of non-premix flames / Judson M. Rogers. 1940. / Includes bibliographical references (leaf 48). / by William Rogers Stern. / B.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 163-175). / Pluripotent stem cells (PSC) hold promise for the study of embryonic development and the treatment of many diseases. Most pluripotent cell research is performed in incubators with a gas-phase oxygen partial pressure (p02) of 142 mmHg. However, embryonic cells in early development are exposed to a local P02 of 0-30 mmHg, and the effects of such conditions on differentiating PSC are poorly understood. Residual PSC within differentiated populations are problematic because of their potential to form tumors in vivo. This is a major safety issue that must be overcome before PSC-based therapies can be used in the clinic. In this study, we differentiated mouse and human embryonic stem cells and mouse induced pluripotent stem cells at different defined P02 on highly oxygen-permeable silicone rubber culture dishes and assessed differentiation to the three germ layers, endoderm, ectoderm, and mesoderm and to cardiomyocytes and assessed residual PSC within differentiated populations. Low P02 drastically affects differentiation of PSC to the three germ layers and cardiomyocytes. Overall, differentiation was higher to endoderm, lower to ectoderm, and higher or the same to mesoderm. Differentiation to cardiomyocytes was greatly enhanced without the need for purification, possibly by lineage selection via increased Mesp1 and Mesp2 expression. Understanding the effects of P02 during differentiation is an important step towards the development of protocols for regenerative medicine. Control of P02 to physiological levels typical of the developing embryo reduced the fraction of PSC within, and the tumorigenic potential of, differentiated populations. Culture under differentiating conditions at low PO2 reduced measured pluripotency markers by up to four orders of magnitude. Upon implantation into immunocompromised mice, low PO2-differentiated PSC either did not form tumors or formed tumors at a slower rate than high PO2 PSC. Low PO2 differentiation could be combined with cell sorting for improved benefits. Low PO2 culture alone or in combination with other methods is a potentially straightforward method that could be applied to future cell therapy protocols to minimize the possibility of tumor formation. / by Jeffrey Robert Millman. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references. / Crystallization is a separation process widely used in several important industries such as food, pharmaceuticals, and specialty chemicals, where crystallization serves as the final step of purification and isolation. Crystallization is a two-step process: nucleation (birth of crystals) and crystal growth. Nucleation can occur via several mechanisms, and the most industrially relevant ones are heterogeneous nucleation (nucleation on a foreign surface), and contact secondary nucleation (nucleation from an existing crystal due to a contact force). Despite the importance of the nucleation process and decades of research, nucleation mechanisms remain enigmatic. This thesis advanced the understanding of the mechanisms of two types of nucleation: contact secondary nucleation, and contact-induced heterogeneous nucleation. By taking advantage of the thermodynamic and kinetic characteristics of glycine system, it is concluded that contact secondary nuclei could originate from both the semi-ordered solute molecules at the interface layer on the surface of existing crystals and directly from parent crystals themselves via the mechanism of micro-attrition depending on the magnitude of the contact force. The contact experiments on functionalized gold plates further confirmed that micro-attrition is not the exclusive mechanism for contact secondary nucleation-contact can induce nucleation even in the presence of only appropriate functional groups. For contact-induced heterogeneous nucleation, by relating nucleation frequency and polymorph with the strength and type of interactions between solute molecules and the templates, it is concluded that contact-induced heterogeneous nucleation share similarities with undisturbed heterogeneous nucleation in terms of attracting and stabilizing pre-nucleation clusters, but they are also fundamentally different in that crystals generated by the former are not chemically interacting with the templates. This thesis also describes the rational design of two small-scale continuous crystallizers, which are taking on increasingly important roles in the next-generation pharmaceutical manufacturing. The first design is a tubular crystallizer that generates crystals of narrow sizes through contact secondary nucleation. The second design is a multi-stage mixed-suspension mixed-product removal (MSMPR) system with a small footprint that works robustly at suspension handling. When optimizing this design with antisolvent crystallization, it was discovered that crystallization kinetic parameters are affected by antisolvent composition independent from supersaturation levels. This thesis highlights, for the first time, that optimizing continuous antisolvent crystallization in MSMPR crystallizers must take into account the effects of antisolvent composition on crystallization kinetics. / by Yuqing Cui. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1985. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 193-199. / by Doros Nicolas Theodorou. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2006. / Includes bibliographical references. / Magnetic fluids are colloidal dispersions of magnetic nanoparticles that are stable with respect to gravitational and moderate magnetic fields because of their small particle size, and to unbounded aggregation due to their surface coatings. The interaction between individual magnetic nanoparticles in a suspension is negligible even under applied magnetic fields. However, when they are incorporated into composite structures they act in concert to provide the desired magnetic response. The dynamic response of such composite structures can be exploited in a wide range of applications including high energy absorption scenarios. The goal of this thesis was to use magnetic nanoparticles as building blocks to create 3D magneto-responsive nanostructures and manipulate their behavior in the presence of an external magnetic field for various applications. Two approaches were followed to create composite structures. In the first approach, rigid magnetic chains composed of magnetic nanoparticles were synthesized. The layer-by-layer technique was used to coat polystyrene beads with magnetic nanoparticles to create novel core-shell structures. The behavior of these structures under an applied magnetic field was modeled and the results were verified experimentally. / (cont.) These magnetic polystyrene beads were then aligned within a microchannel by an external magnetic field and linked together using sol gel chemistry to yield rigid superparamagnetic chains. Linking the magnetically aligned beads with a flexible linker yielded flexible superparamagnetic chains. These permanently-linked magnetic chains can be used as micro-mixers in a microfluidic channel under a rotating magnetic field. The reorientation dynamics of these chains under an external magnetic field was modeled. Microcontact printing was employed to tether the flexible chains in a desired pattern on a glass surface. Tethered flexible magnetic chains have potential applications in microfluidics and separations. Rings and icosahedra shaped electrostatically charged templates were generated from the self-assembly of mixtures of surfactants in an aqueous solution and were investigated for their application in the synthesis of non-spherical magnetic structures. The magnetic response of the magnetic rings was modeled and the results were verified experimentally. "Templateless" aggregation of magnetic nanoparticles using radiation crosslinking was also investigated. / (cont.) Aqueous magnetic nanoparticles stabilized with a radiation crosslinkable polymer resulted in magnetic gels at high dosage amount of the ionizing radiation. Magnetic gels can have potential applications in biological areas. Different size monodisperse magnetic nanoparticles were synthesized via an organic synthesis route, and the effect of size on the Nel relaxation behavior of the fixed magnetic nanoparticles was investigated. Theoretical analysis suggested that incorporation of magnetic nanoparticles with high relaxation times in a matrix can be used to absorb energy. The energy penalty associated with the deflection of the magnetic dipole against the field should result in the stiffening of the matrix. This was demonstrated both experimentally and theoretically. Drop ball impact test was performed on foam embedded with infinite Nel relaxation nanoparticles and the deflection profile of the foam was monitored both in the presence and in the absence of a magnetic field. The deflection of the foam by the ball was modeled to calculate the strain profile developed by the foam, which was then converted into the equivalent amount of energy absorbed by the foam and the magnetic nanoparticles. / (cont.) A method of electrospinning was used to encapsulate magnetic nanoparticles in a polymeric matrix to create field responsive nanofibers for various applications. The magnetization properties of the nanofibers were also characterized and their behavior under an applied magnetic field was modeled. / by Harpreet Singh. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1989. / Title as it appeared in MIT Graduate list, June, 1989: Siloxane-nylon-6 diblock copolymers for emulsification and toughening of blends. / Includes bibliographical references. / Cary Alan Veith. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2002. / Includes bibliographical references (leaves 123-132). / Fullerenes are molecules comprised entirely of sp²-bonded carbon atoms arranged in pentagonal and hexagonal rings to form a hollow, closed-cage structure. Buckyballs, a subset which contains C₆₀ and C₇₀, are single-shell molecules while fullerenic nanostructures can contain many shells and over 300 carbon atoms. Both fullerenes and nanostructures have an array of applications in a wide variety of fields, including medical and consumer products. Fullerenes were discovered in 1985 and were first isolated from the products of a laminar low-pressure premixed benzene/oxygen/argon flame operating at fuel-rich conditions in 1991. Flame studies indicated that fullerene yields depend on operating parameters such as temperature, pressure, residence time, and equivalence ratio. High-resolution transmission electron microscopy (HRTEM) showed that the soot contains nanostructures, including onions and nanotubes. Although flame conditions for forming fullerenes have been identified, the process has not been optimized and many flame environments of potential interest are unstudied. Mechanistic characteristics of fullerene formation remain poorly understood and cost estimation of large-scale production has not been performed. Accordingly, this work focused on: 1) studying fullerene formation in diffusion and premixed flames under new conditions to identify optimal parameters; 2) investigating the reaction of fullerenes with soot; 3) positively identifying C₆₀ molecules in HRTEM by tethering them to carbon black; and 4) providing a cost estimation for industrial fullerenic soot production. / (cont.) Samples of condensable material from laminar low-pressure benzene/argon/oxygen diffusion flames were collected and analyzed by high-performance liquid chroma- tography (HPLC) and HRTEM. The highest concentration of fullerenes in a flame was always detected just above the height where the fuel is consumed. The percentage of fullerenes in condensable material increases with decreasing pressure and the fullerene content of flames with similar cold gas velocities shows a strong dependence on length. A shorter flame, resulting from higher dilution or lower pressure, favors the formation of fullerenes rather than soot, exhibited by the lower amount of soot and precursors in such flames. This indicates a stronger correlation of fullerene consumption to soot levels than of fullerene formation to precursor concentration. The maximum flame temperature seems to be of minor importance in formation. The overall highest amount of fullerenes was found for a surprisingly high dilution of fuel with argon. The HRTEM analysis showed an increase of the curvature of the carbon layers, and hence increased fullerenic character, with increasing distance from the burner up to the point of maximum fullerene concentration, after which it decreases, consistent with the HPLC analysis. The soot shows highly ordered regions that appear to have been cells of fullerenic nanostructure formation. The samples also included fullerenic nanostructures such as tubes and spheroids including highly-ordered multilayered or onion-like structures. Studies of turbulent-like benzene/oxygen/argon diffusion flames showed that these flames produce fullerenes over a wider range of heights than laminar flames but with lower yields. / (cont.) No discernible trend could be detected in the data and the fullerene results were not easily reproducible indicating that such flames are not suitable for fullerene formation. Soot samples were also collected from a well-characterized laminar premixed benzene/oxygen/argon flat flame under new conditions and analyzed by HPLC and HRTEM. Flame studies using secondary injections of benzene or acetylene show that two-stage flames are unsuitable for fullerene production. It seems that secondary fuel has an adverse effect on the formation of fullerenes and creates conditions that are similar to the early stages of a single-stage flame prior to soot formation. This means that fuel must go through the combustion process to form fullerenes and that they cannot be formed simply by organic pyrolysis. Additionally, fullerene data collected in this study show significantly higher yields than in a previous study and the absence of a concentration drop-off. The coexistence of fullerenes and soot does not support but also does not rule out that fullerenes are consumed by soot, as was suggested by diffusion flame data. Given the discrepancy in the data, fullerene consumption was studied in experiments involving pure fullerenes being sublimated into a passing argon gas stream. This gas stream then passed through a carbon black bed. As the fullerenes passed through the bed, a certain percentage reacted with the surface of the particles and the non-reacted material was collected downstream. Experiments at different temperatures indicate that fullerenes are indeed consumed by soot particles but that the consumption is quite slow. / (cont.) The rate coefficient obtained resembles those seen for surface diffusion controlled reactions or for heterogeneous reactions. Extrapolation of the reaction coefficient to flame conditions would indicated that this type of fullerene consumption is not nearly enough to explain the consumption observed in fullerene-forming flames, meaning that fullerenes are consumed by other mechanisms. HRTEM analysis of carbon black with and without tethered fullerenes shows that fullerenes can in fact be observed in TEM micrographs. In this experiment, functionalized C₆₀ molecules were attached to the surface of carbon black particles with a chemical tether. The resulting compound was analyzed by HRTEM and compared with similar analysis of untreated carbon black. The post-treatment carbon black not only has an order of magnitude greater concentration of apparent fullerene structures but size distribution data shows a significant peak at the C₆₀ diameter for the treated sample whereas no peak is observed for the untreated sample. This indicates that the fullerenes have indeed been attached to the particle surface and that they can definitively be seen in images produced from HRTEM. Lastly, a model was built to estimate the cost of the large scale production of fullerenic soot. This model was based on current carbon black technology and takes into account operating parameters specific for fullerene production. Sensitivity analyses performed on the model indicate that soot yield and fuel price are the most important factors in determining production cost while electricity costs are minimally important. / (cont.) It was seen that operating pressure and equipment lifetime are negligible in the final cost. Overall, combustion holds immense promise to be a much cheaper and more efficient alternative to the current method of commercial fullerene production. / by Anish Goel. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2008. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references (p. [109]-122). / The quantification and manipulation of biological entities from a physiological sample is extremely important for a broad range of applications in medical diagnostics, therapeutics, and basic science research. From a diagnostics standpoint, the cells, proteins, and nucleic acids that compose our bodies contain an enormous amount of information that can indicate the presence of, progression of, or even susceptibility to a given disease. However, extracting this information is often quite challenging. New tools are constantly being developed to make diagnostic testing more accurate, less invasive, faster, and less expensive. To this end, this thesis describes that advent of technologies to (1) precisely pattern biologically- and magnetically-active beads in hydrogel substrates for cell sorting and pattering, (2) synthesize morphologically and chemically-complex microparticles in a high-throughput fashion, and (3) perform rapid and accurate multiplexed biomolecule quantification using such particles. Bead-Patterned Hydrogels are a class of materials developed in this thesis that consist of microbeads precisely patterned in poly(ethylene glycol) (PEG) matrices. Using microfluidics and projection lithography on a standard microscope, magnetically-active or protein-decorated beads were patterned in close-packed or disperse-bead patterns on glass substrates with high resolution over large areas. Using slight alterations to ... bio-inert PEG matrix, or exposed from the PEG surface. It was shown that bead-patterned hydrogels could be used for the phenotype-specific sorting or patterning of lymphocytes. As was observed in the synthesis of bead-patterned hydrogels, free-radical polymerization is inhibited near microfluidic channel walls due to oxygen diffusion through the porous polydimethoxysilane (PDMS) elastomer composing devices. / (cont.) By exploiting this phenomenon using ... an all-PDMS device, C graphy was developed. In stark contrast to traditional methods for anisotropic particle synthesis, this one-phase process provides a simple method to synthesize microparticles with complex morphologies and/or multiple adjacent chemistries in a high-throughput fashion. The processes is broadly applicable to any free-radical reacting monomer. For improved resolution and sharpened interfaces between adjacent chemistries ... / by Daniel Colin Pregibon. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2009. / Includes bibliographical references. / Since the first discovery of polymeric conductors in 1977, the research area of "organic electronics" has grown dramatically. However, methods for forming thin films comprised solely of conductive polymers are limited by the rigid nature of the conjugated backbone. Neither spin casting from solution nor melt processing can be used. To answer to this challenge, a solvent-free method of oxidative chemical vapor deposition (oCVD) to synthesize conductive poly (3, 4-ethylenedioxythiophene) (PEDOT) films was demonstrated. The substrate temperature systemically controls the conjugation length, resulting in films with conductivity of 9.1 x 10-4 to 348 S/cm. The highest conductivity was about 1000 S/cm. The doping level could also be tuned with substrate temperature. Consequently, the work function was varied from 5.1 to 5.4 eV. The polymerization rate could be modulated with various oxidants, which significantly affects the surface morphology of PEDOT film. With milder oxidant, the surface morphology was highly nano-porous. Conformal coverage of PEDOT was also observed on trench structures and paper mats. Furthermore, with this one-step method, PEDOT film could be grafted on various kinds of organic substrates. Huge increase in adhesion strength was consistently observed. With this grafting technique, nanometer-scale PEDOT pattern was firstly obtained on flexible substrates down to 60 nm. / (cont.) A click chemistry functionalizable poly (propargyl methacrylate) (PPMA) films also were prepared via initiated chemical vapor deposition (iCVD). PPMA itself exhibits e-beam sensitivity and hence can be directly patterned via electron beam (e-beam) lithography without requiring a conventional resist layer. With this PPMA layer, a nanopatterned multi-functional surface was also fabricated and we demonstrated the covalent functionalization of two independent components in a one-pot, self-sorted area-selective process, performed in an aqueous solution at room temperature, having conditions which are bioompatible. Finally, we report a novel nano-adhesive layer deposited by the iCVD process. An epoxy-containing polymer, poly (glycidyl methacrylate) (PGMA) was used as a nano-adhesive layer. No leakage was observed up to the test pressure of 50 psia from the resulting microfluidic devices. / by Sung Gap Im. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 136-143). / The increasing global levels of sulfur content in crude oil have motivated the development of alternate desulfurization technologies. Microbial desulfurization or biodesulfurization (BDS) has gained interest due to the ability of certain biocatalysts to desulfurize compounds that are recalcitrant to the currently employed hydrodesulfurization (HDS) technology. Two of the major obstacles to commercialization of BDS are mass transport limitations and the inability to maintain biocatalyst activity for long periods of time. In this work, the mass transport limitations were studied in a small-scale model system consisting of a resting cell suspension of Rhodococcus erythropolis IGTS8 mixed with hexadecane containing dibenzothiophene (DBT). DBT has become the model compound in BDS studies because its alkyalted derivatives are highly recalcitrant to HDS. Biocatalyst aggregation was found to be significant at cell densities higher than approximately 5 g DCW/L, with aggregates reaching mean diameters of over 100 gm. The diffusion of DBT through the aggregates was the major mass transport limitation in the system. Agitation at a power input per volume of over 10 W/L was estimated to be enough to overcome all mass transport limitations in the BDS system. 2-hydroxybiphenyl retention by the biocatalyst was correlated with the reduction in biocatalyst activity. The biocatalyst affinity for HBP is on par with that of the oil phase and about 60 times that of the aqueous phase. Inhibition of three of the four enzymes in the BDS pathway by HBP was determined to be the cause for the reduction in biocatalyst activity. This conclusion was reached from the finding that the concentrations of HBP that affect the enzymes are significantly lower than the estimated cytoplasmic HBP concentrations during BDS. A mathematical model based on enzyme inhibition predicted the reduction in BDS accurately. / by Andres Abin-Fuentes. / Ph.D.