Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1996. / Includes bibliographical references (p. 197-214). / by Pak K. Yuet. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1958. / Includes bibliographical references (leaf 49). / by William Francis Reilly. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2008. / Includes bibliographical references (p. 143-155). / Block copolymers in solution can self-assemble in to a variety of morphologies, with features on the nanometer length scale. This has lead to significant recent research into this assembly process and a wide range of potential applications. The exchange of block copolymer molecules between micelles and solution is very slow compared to the exchange kinetics observed for low molecular weight surfactant micelles. A favorable result of these slow exchange kinetics is the ability to retain a micellar morphology during casting from selective solvents onto solid substrates; this morphology becomes kinetically trapped in the final thin film upon solvent evaporation, even in cases for which the copolymer composition would suggest a transition to a different equilibrium heterogeneous phase. Control of the structural parameters of the micellar thin films, including micelle core size, micelle corona size and distance between adjacent micelle cores is important for thin film applications. Here we demonstrate the ability to control these structural parameters using polystyrene-block-poly(acrylic acid) (PS-b-PAA) as a model block copolymer system that assembles into spherical micelles in toluene. Several strategies were employed: varying the block copolymer molecular weight, adding PS homopolymer into the micellar solution, and also by the combination of different micellar solutions. Patterning of micelle films on the micron length scale is accomplished via two PDMS stamp-based soft lithographic techniques. PS-b-PAA spherical micelle thin films cast from toluene can undergo rearrangement upon exposure to solvents selective for the PAA block. The solvent swells the PAA micelle core and ruptures the glassy PS corona, a process we termed cavitation. Here we have investigated the conditions required for this cavitation process to occur and the end-state polymer morphology of close-packed films of PS-b-PAA micelles following treatment with a series of short alkyl chain alcohols or aqueous solutions of varying pH and ionic strength. In addition to the effects of solvent conditions, we show that the cavitation process is influenced by the molecular weight of the PS block and is thermally reversible. / (cont.) Following cavitation, the nanopatterned regions of exposed PAA are available for conjugation chemistry, demonstrated here through selective linking of a fluorescently labeled protein. Cavitation was also observed in polystyrene-block-poly(2vinyl pyridine) (PS-b-P2VP) spherical and cylindrical micelles. Biocompatible oils are used in a variety of medical applications ranging from vaccine adjuvants to vehicles for oral drug delivery. To enable such nonpolar organic phases to serve as reservoirs for delivery of hydrophilic compounds, we explored the ability of block copolymer micelles in organic solvents to sequester proteins for sustained release across an oil-water interface. Self-assembly of the block copolymer, poly (ecaprolactone)-block-poly(2-vinyl pyridine) (PCL-b-P2VP), was investigated in toluene and oleic acid, a biocompatible naturally- occurring fatty acid. Micelle formation in toluene was characterized by dynamic light scattering (DLS) and atomic force microscopy (AFM) imaging of micelles cast onto silicon substrates. Cryogenic transmission electron microscopy confirmed a spherical morphology in oleic acid. Studies of homopolymer solubility implied that micelles in oleic acid consist of a P2VP corona and a PCL core, while P2VP formed the core of micelles assembled in toluene. The loading of two model proteins (ovalbumin (ova) and bovine serum albumin (BSA)) into micelles was demonstrated with loadings as high as 7.8 % wt of protein per wt of P2VP in oleic acid. Characterization of block copolymer morphology in the two solvents after protein loading revealed spherical particles with similar size distributions to the asassembled micelles. Release of ova from micelles in oleic acid was sustained for 30 hours upon placing the oil phase in contact with an aqueous bath. Unique to the situation of micelle assembly in an oily phase, the data suggest protein is sequestered in the P2VP corona block of PCL-b-P2VP micelles in oleic acid. More conventionally, protein loading occurs in the P2VP core of micelles assembled in toluene. / by Andrew Craig Miller. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1938. / Includes bibliographical references (leaf 56). / by James Walton Wilson. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1994. / Includes bibliographical references (p. [441]-470). / by M. Reza Mehrabi. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 157-163). / Humans, like most other jawed vertebrates, are equipped with an adaptive immune system that can respond to diverse pathogens. Mature T cells, one of the most important immune cells generated from the thymus through a rigorous selection processes, are key orchestrators of the immune responses. Although many of the key signaling molecules in T cells have been discovered, the underlying mechanisms of how some of these signaling molecules interact with each other in space and time to trigger T cell activation have not yet been established. Furthermore, recent experimental results demonstrate that the membrane is a highly organized structure with some membrane proteins inhomogeneously distributed into clusters, which are often called protein islands or protein clusters. The roles of these clustered proteins remain to be established. For my thesis, to gain insights into the roles of protein islands in early T cell signaling, I have focused on important clustered proteins such as the T-cell receptor (TCR) and Linker of activated T cells (Lat). Active ZAP-70 molecules, which phosphorylate tyrosine residues of Lat molecules, are generated from the clustered TCR molecules. Using spatial Gillespie simulation and mathematical modeling, I found that clustered proteins may suppress the probability of spurious triggering of T cells. This finding may suggest an important role of clustered proteins, which may be relevant to other signaling networks and other cell types with spatially clustered proteins in the membrane. In addition, I have examined how the spatial organization of membrane proteins and the diffusivity of molecules affect the steady-state levels of key molecules required for T-cell activation: RasGTP and fully phosphorylated ITAM. I have also studied the correlation between the peptide repertoire presented by antigen-presenting cells in the thymus and the generation of autoreactive T cells as well as the TCR repertoire of peripheral T cells. / by Woo K. Chung. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1999. / Includes bibliographical references (p. 421-436). / The effective delivery of fragrances in consumer products is a challenging problem. For example, fragrances in commercial laundry detergents or fabric softeners may not adsorb efficiently onto clothes during the vigorous washing process. In addition, fragrances consist of volatile ingredients that may evaporate prematurely while clothes are being dried, thus leaving little fragrance remaining on the cleaned fabrics. In order to enhance fragrance delivery, controlled-delivery systems are beginning to be utilized in industry. However, the design of these systems in industry is often conducted by costly trial-and-error experimentation. The objective of this thesis was therefore to develop a fundamental understanding of how the physical characteristics of a controlled-delivery system could be rationally designed to enhance fragrance delivery. This thesis focused primarily on the design of a microparticle controlled-delivery system to enhance the delivery of fragrances in commercial laundry detergents and fabric softeners. The microparticle controlled-delivery system is conceptualized to possess the following three desirable features that enable it to enhance fragrance delivery in commercial laundry products: 1. Fragrance loading in microparticles can prevent premature release of the fragrance and adverse interactions between the fragrance and other ingredients in a product formulation both during storage and during the application process. 2. Fragrance adsorption onto a targeted surface can be improved through an optimization of the microparticle physical properties, such as size, hydrophobicity, and surface charge density. 3. Fragrance release can be sustained over prolonged periods of time because of the diffusional resistance provided by the microparticles. A feasibility analysis was initially conducted to demonstrate that the microparticles indeed possessed these three features. Experimental and theoretical studies were then conducted to understand how these three microparticle features could be rationally designed and optimized. In order to facilitate a rational design of fragrance loadings in microparticles, a molecular thermodynamic theory was developed to predict fragrance loadings in both polymeric microparticles that were prepared by a solvent evaporation process and wax microparticles that were prepared by a hot melt-freezing process. The developed theory provided reasonable predictions of experimentally measured fragrance loadings in both the polymeric and wax microparticle systems. Accordingly, the theory can be utilized to choose a material to load a given fragrance and to provide guidelines for optimizing the manufacturing process in order to produce microparticles with desired fragrance loadings. Since the theory does not require input of any experimentally measured fragrance loadings, use of the theory to rationally design and optimize a microparticle system for the loading of a given fragrance can significantly reduce the amount of time and resources required to conduct an experimental design and optimization. Fundamental studies were also conducted with unprotected fragrances to identify the mechanisms that inhibit fragrance adsorption onto fabrics in order to better design microparticles that could enhance fragrance adsorption. These studies were performed under simulated laundry conditions using well-characterized surfactants that were representative of those found in commercial laundry products. The adsorption of relatively hydrophilic fragrances onto fabrics was found to be limited by the relatively high solubility of these fragrances in the aqueous solutions utilized to wash the fabrics. On the other hand, the adsorption of relatively hydrophobic fragrances onto fabrics was found to be limited by fragrance solubilization in surfactant micelles that may be present in the commercial laundry solutions. These studies led to the development of a theoretical model to predict the composition of an adsorbed fragrance mixture from the composition of the mixture in the bulk washing solution. Since the aroma associated with a fragrance depends on the composition of the fragrance, the model enables a manufacturer to a priori manipulate the fragrance mixture composition in a laundry product in order to produce the desired aroma on the fabric surface. The developed molecular-level understanding of the mechanisms affecting fragrance adsorption onto fabrics was also extended to rationalize trends observed in fragrance adsorption onto both fabrics and hair that were washed using commercial laundry and hair care products, respectively. The mechanisms identified to inhibit the adsorption of unprotected fragrances onto fabrics can be circumvented by loading the fragrances into microparticles, and therefore, a preliminary study was conducted to determine the factors th.J.t influence microparticle adhesion onto a targeted surface. In particular, the effect of rnicroparticle size on microparticle adhesion onto cotton and polyester fabrics was investigated. The release of unprotected fragrances during the drying of fabrics was also investigated to determine a reference for comparing the release of fragrances from microparticles. Fragrances were most quickly released at the start of the drying process when the fabrics were relatively wet. This release was governed by the diffusional flux of the fragrance from the aqueous liquid film present on the wet fabrics. On the other hand, when the fabrics became relatively dry, direct interactions between the fragrance molecules and the fabric surface controlled the fragrance release behavior. In addition, preliminary studies were conducted to quantitatively characterize the ability of the microparticles to sustain fragrance release from fabrics over the course of three to seven days. / by Ginger Tse. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, February 2017. / "October 2016." Cataloged from PDF version of thesis. / Includes bibliographical references (pages 255-295). / Electrochemical separation methods are promising due to their modularity, fast kinetics and potential integration with renewable sources. However, they are still limited in application due to high energetic costs and lack of chemical selectivity. This work explores redox-electrodes as a platform for targeting aqueous and organic contaminants with high separation factors, in the contexts of environmental water remediation, chemical product purification in organic synthesis, metal-recovery and bio-separations. The design of selective stimuli-responsive interfaces is a crucial challenge for advanced electrochemical processes. Whereas redox-electrodes are well known in sensing, catalysis and energy storage, here we focus on their unique potential for selective ion removal - cases in which one dilute compound is targeted in the presence of large excess of competing electrolyte. In particular, organometallics and associated metalcomplexes offer an attractive material platform, due to their flexible metal-ligand design and as a consequence, extensive control allowed of their electronic properties. The first major thrust is the molecular design of various organometallic species for specific interactions with charged compounds in solution. We developed a series of heterogeneous, nano-structured metallocene interfaces to control the selective sorption and release of anions, cations, and even proteins, based on electrochemical potential. In parallel, through a combination of electronic structure calculations and spectroscopy, we unraveled the unique binding mechanism between ferrocenium and organic ions demonstrating an unusual redox-mediated hydrogen-bonding between cyclopentadienyl and carboxylates; and utilize this knowledge to further tune our redox-systems to enhance chemical selectivity. We expanded our organometallic set to various bi-pyridines and functionalized metallocenes, and studied various problems ranging from reactive separations to catalytic remediation of contaminants of emerging concern. A second major thrust consists in utilizing asymmetric pseudo capacitors as the next generation configuration for electrochemical separation devices. Asymmetric systems were shown to have much higher energy storage capabilities as well as separation efficiencies. We focused on counter-electrode design, in which the redox reaction at the cathode works in tandem with the anode, thus maintaining the water chemistry by suppressing parasitic reactions which otherwise lower current efficiency. From a fundamental perspective, the novel interaction mechanisms explored in this thesis were shown to have broader implications in deionization, sensing, catalysis and energy storage. For chemical engineering, this work demonstrated redox-based electrochemical methods as an energy-efficient and sustainable route to process intensification, and paved their way for practical implementation in industry. / by Xiao Su. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2003. / Includes bibliographical references (leaves 120-123). / Composites of polymer matrix and filler particles constitute an important class of materials. Filler particles are used to reduce overall cost and to improve the mechanical properties of the polymer matrix. Until recently, there exists a trade-off between stiffness and toughness in using filler particles in polymer composites. This thesis studies the mechanisms whereby both stiffness and toughness can be enhanced using rigid mineral filler particles. The mechanisms of deformation and fracture of isotactic polypropylene filled with CaCO3 particles were studied. In slow tension, addition of fillers increased the modulus and decreased the yield stress independent of filler type. An optimum size of particles was found to improve Izod impact energy up to four times that of the unfilled matrix. The toughening mechanisms at work were plastic deformation of interparticle ligaments following particle-matrix debonding with additional contribution coming from crack deflection toughening. The failure of too large or too small particles to toughen the matrix was attributed to poor dispersion. A study on the volume evolution of these composites during deformation revealed that measurement of volume strain can be used to identify the onset of debonding. It also provided a new evidence for the existence of an interphase layer between the filler particles and the polymer matrix. This layer is comprised of polypropylene chains strongly bound to the surface of the particles. The thickness of this layer was estimated to be 20 nm. The effect of particle-matrix interaction was investigated in a study of composites of isotactic polypropylene and glass spheres. / (cont.) Silane treatment was used to modify the surface energy of glass. A model study performed on bulk polypropylene and glass samples demonstrated that the use of mixtures of silanes - one with a perfluoro-alkane endgroup and one with an alkane endgroup - can be used to vary the surface energy of the glass and also the adhesion strength between the glass and polypropylene. The debonding process in composites of polypropylene and surface-treated glass particles was investigated by measuring the local volumetric strain during deformation. Weaker particle-matrix interaction was demonstrated to result in earlier debonding, which in turn produces higher fracture toughness. In a given mineral filler-polymer matrix system, the mechanical properties of the matrix polymer are expected to determine whether the mechanism outlined here is applicable. Based on this and previous studies, the most important parameter in the improvement in toughening is the plasticity of the matrix as indicated by the glass transition temperature and the yield stress. / by Yonathan Setioputra Thio. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1992. / Includes bibliographical references (leaves 160-175). / by Victoria Sluzky. / Ph.D.