Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1999. / Includes bibliographical references (p. 170-181). / by João Paulo Dantas Aumond. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 175-184). / Understanding the mechanisms that govern the structure and function of synthetic polymer thin films is of fundamental and practical significance for developing a diverse range of functional surfaces including antifogging coatings, switchable surfaces and stimuli-responsive hydrogels. The first part of this thesis is focused on extending hydrogen-bonding driven polymer thin film assembly by developing a novel systematic framework in which poly(vinyl alcohol) (PVA) can be incorporated into LbL assembled multilayer thin films. Incorporation of PVA into multilayer thin films is advantageous due to its biocompatibility and ease of chemical functionalization and cross-linking. The optimal assembly conditions of PVA multilayer films were discovered through extensive investigation on the degree of PVA hydrolysis, molecular weight and the type of weak polyacids. Subtle variations due to the prevalence of PVA acetate moieties, characterized by the degree of hydrolysis, were shown to cause drastic differences both in self-assembly with its hydrogen-bonding partners as well as its overall pH-stability. The library of materials that can be hydrogen-bonded with PVA was further extended by assembling films with biologically relevant molecules such as tannic acid. This leads to enhanced pH-stability as a result of the high pKa value of tannic acid. Multiple stacks of hydrogen-bonded LbL structures with differing composition and properties were also assembled resulting in complex heterostructured architectures that sequentially dissolve with an increase in local pH conditions. The abundance of free hydroxyl and carboxylic acid groups in the PVA/PAA multilayer allows for enhanced pH stability up to physiological conditions using thermal and chemical methods which offer numerous opportunities for post-assembly functionalization. This was demonstrated by functionalizing PVA/PAA multilayers with poly(ethylene glycol methyl ether) (PEG) to generate a novel antifogging coating with switchable surface properties. To facilitate the characterization of the antifogging coatings a new protocol was developed that enables quantitative analysis of antifogging performance via real-time monitoring of transmission levels as well as image distortion. The antifogging PVA/PAA multilayers were shown to exhibit "zwitter-wettable" behavior, whereby the multilayer film exhibited a facile, rapid absorption of molecular-level water into a film from the gas phase while simultaneously exhibiting very high contact angles for macroscopic liquid drops of water placed on the surface of the same film. An additional step of functionalizing this nano-blended PVA/PAA multilayer with PEG segments produced significantly enhanced antifog and even frost-resistant behavior which was due to the increase in the nonfreezing water capacity of the multilayer film. The PEG-functionalized PVA/PAA multilayers exhibited transient and reversible water contact angle behavior which was studied by both goniometry and dynamic tensiometry. The time-dependent wetting behavior of these coatings was attributed to the transient surface rearrangement of hydrophilic functional groups towards the surface in response to exposure to a liquid water environment. Using a simple first-order thermally-activated model, the kinetics of surface rearrangement was explored in detail. Finally, a model system was designed to study the zwitter-wettable phenomenon in more detail. The complex network of hydrophilic and hydrophobic moieties was decoupled into a heterostructured film consisting of a hydrophilic reservoir and a hydrophobic capping layer. Surface chemistry and roughness were previously believed to be the main factors controlling condensation of water on the film, however, the capacity of the film to transport water molecules was also found to be important for designing functional zwitter-wettable films. / by Hyomin Lee. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, February 2004. / Includes bibliographical references (p. 118-127). / The highly complex nature of developmental cell fate decisions is exemplified by murine embryonic stem cell (ES cell) differentiation, for which almost two decades of study has identified a small set of putative individual molecular cues which are difficult to generalize broadly or discern determinative signals from. Here we offer a combined experimental/computational investigation aimed at elucidating in a systematic manner important synergies between multiple extracellular cues, especially from cytokines and matrix proteins together, and consequent critical intracellular signals within a multi-pathway network governing mouse ES cell differentiation. A factorial design was used to evaluate responses of ES cells to combinations of leukemia inhibitory factor (LIF) and fibroblast growth factor-4 (FGF4) as soluble signals along with fibronectin (Fn) and laminin (Ln) as adhesion substrates. Factorial analysis revealed significant and unexpected cytokine/matrix synergistic effects. These results showed that the outcome elicited by a specific factor depends on the context in which that factor is presented to the cell. For example, LIF is known to completely inhibit the differentiation of ES cells. Its ability to prevent differentiation is unaffected by the presence of FGF4 or Fn. However, when LIF is present with both FGF4 and Fn, increased differentiation is observed. In order to understand underlying mechanistic regulatory causes for these kinds of complicated synergies, we developed a mathematical model capable of decomposing differentiation and proliferation cell fates from overall cell population dynamics. This decomposition showed that the various cue combinations governed one or another, or sometimes multiple, of these cell fates. / (cont.) Using this model as a framework for interpreting population-averaged differentiation data allowed us to follow sub-population dynamics in mixtures of differentiating cells and was critical for correctly interpreting subsequent signaling data. Finally, we applied partial least square analysis to proteomic data for 31 different intracellular kinases, determining network signals critically correlative with the cell fate decisions. Two significant predictions arising from this analysis were confirmed independently: (a) inhibition of translocation of PKCepsilon results in a decrease in the growth rate of differentiated cells; and, (b) inhibition of Rafl also leads to a decrease in the growth rate of differentiated cells. We believe that our quantitative, systems-oriented approach bears promise for further advances in understanding regulation of complex cell fate processes in development. / by Wendy A. Prudhomme. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2011. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student submitted PDF version of thesis. / Includes bibliographical references. / Nanotube arrays, composed of materials such as carbon, titania, and zinc oxide, have shown potential as conductors, energy conversion devices, actuators, and adhesives. Such nanoscale constructs are particularly novel for their high area-to-volume and length-to-diameter aspect ratios that lead to physical and chemical properties more interesting than their bulk counterparts. However, the stimuli-responsiveness of nanotube arrays has seldom been explored, mostly due to the inertness of the materials typically utilized to create them. Here I introduce a new concept of designing and synthesizing surface-bound stimuli-responsive polymer nanotubes with dynamic mechanical properties. Polyelectrolyte multilayers (PEMs) composed of poly(allylamine hydrochloride) and poly(acrylic acid) were chosen as the nanotube building blocks for their ability to undergo pH-triggered swelling-deswelling transitions. The swelling behavior was first demonstrated in the in situ synthesis of gold nanoparticles in the PEM; upon suitable post-assembly treatment, the PEM undergoes substantial molecular rearrangements that generate free amine groups available for gold salt binding. Characterization of the size and distribution of the gold nanoparticles as a function of assembly condition and post-assembly treatment, and in situ ellipsometry thickness measurement of the PEM film during the swelling transition provided further insights into the swelling behavior. These studies ultimately led to the design and synthesis of reversibly swellable PEM nanotube arrays via layer-by-layer assembly on porous templates. The template-based approach allows straightforward control over the length, diameter, orientation and lateral arrangement of the resultant tube array, which can be challenging with other synthesis methods. Activation of the swelling transition resulted in dramatic changes in the length and diameter of the tube arrays as characterized in situ via confocal laser scanning microscopy, and in the effective modulus of the nanotube arrays as measured by AFM-based nanoindentation. Parallel to experimental work, finite element analysis of simulated indentation on the nanotube arrays showed deformation mechanisms and a discontinuous stress-and-strain field different than that of a flat film. Template-based nanotube synthesis is further applied to the assembly of nanotubes with thermal- and magnetic-responsiveness, as well as incorporating cell-receptor-interacting biopolymers. / by Khek-Khiang Chia. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1983. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE / Includes bibliographical references. / by Hisham Mohamed Ettouney. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1998. / Includes bibliographical references. / by Diane Rintzler Yen. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1999. / Includes bibliographical references. / by Jeffrey J. Sperinde. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references. / The spray-assisted layer-by-layer (LbL) technique has been investigated for creating multi-walled carbon nanotube (MWNT) films on porous electrospun fiber mats via LbL assembly of surface-functionalized MWNTs. Negative and positive charges were introduced on outer walls of MWNTs by surface functionalization to enable the assembly of MWNTs into multilayer films without binder via the LbL technique. Conformal coating of MWNT films on individual electrospun fibers was achieved by applying a pressure gradient across the electrospun fiber mat to generate flow throughout the porous membrane during the spray-LbL deposition. The resulting MWNT films were shown to have interpenetrating network of unbundled MWNTs with nanoporous texture, which is well suited as electrode material for numerous applications. These LbLMWNT/ electrospun fiber electrodes were utilized for applications in chemical sensing and energy storage as described below. First, the LbL-MWNT/electrospun fiber electrodes were employed as flexible chemiresistive sensors for real-time detection of a nerve agent simulant (dimethyl methylphosphonate (DMMP)). Available functional groups (-NH2 and -COOH) on the MWNT films offer a direct route for covalently attaching a receptor of interest to the MWNTs, in order to tailor the chemical specificity in a modular fashion. Here, a thiourea-based receptor was covalently attached to the -NH 2 functional groups on the MWNT/ES fiber electrodes to enhance sensitivity toward DMMP via hydrogen bonding interaction, resulting in an up to 3-fold increase in sensing response. Chemiresistive sensors based on the engineered textiles displayed reversible responses and detection limits for DMMP as low as 10 ppb in the aqueous phase and 5 ppm in the vapor phase. Employing the LbL-MWNT/electrospun fiber electrodes described above, we created hierarchical porous (HP) MWNT electrodes by removing the electrospun fiber substrate. The resulting HP-MWNT electrodes, which were self-standing and tens of micron in thickness, contained 3D interconnected macropores and mesoporous network of LbL-MWNT films. HP-MWNT electrodes can deliver a high gravimetric energy of ~100 Wh kg-1 at a gravimetric power of -25 kW kg' in lithium nonaqueous cells. Compared to similar MWNT electrodes without macropores, HP-MWNT electrodes exhibited superior rate capability with an up to 10-fold increase in energy retention when the power was increased from ~100 W kg-1 to ~100 kW kg~1 . These HP-MWNT electrodes possess great potential as electrode materials for high-rate electrochemical energy storage applications such as electric vehicles. In summary, this thesis presents a versatile and easily scalable strategy for depositing functionalized MWNT films on 3D porous substrates to create tailored nanostructured electrodes with for various applications, including flexible chemical sensors and energy storage devices. / by Kittipong Saetia. / Ph. D.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1961. / Vita. / Includes bibliographical references (leaves 248-254). / by Frederick W. Tausch, Jr. / Sc.D.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1959. / Vita. / Includes bibliographical references (leaves 236-240). / by Chong Yong Yoon. / Sc.D.