Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2018 / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 123-137). / Electroactive polymeric materials have garnered considerable interest due to their potential applications in advancing electrochemical energy storage, sensing, catalysis, and separations systems. Electroactive polymers include conducting polymers with a-conjugated backbones and redox polymers with localized redox-responsive moieties. The electro-responsive property of both conjugated and redox polymers is highly impacted by the efficient transport of counter-ions within polymers to maintain charge neutrality. The interactions at the molecular interface between the polymer and target entities ultimately dictate the performance of electroactive materials in the aforementioned applications. Nanostructures provide a shortened diffusion path for the transport of electrolyte ions or target molecules during a reversible redox process. The large interfacial area arising from an improved morphology allows efficient utilization of polymeric materials. / Consequently, the union of nanostructures and electro-responsiveness has proven to be a powerful strategy to enhance the merit of electroactive polymers in the design of next generation energy storage devices, sensors, catalysts and separation platforms. In this thesis, we focused on developing novel synthesis strategies for nanostructured electroactive polymeric composites. Two different synthesis approaches for the polymeric component were realized by exploiting the inter-molecular interactions between monomeric units and other entities during an electrochemical polymerization process. In the first approach, a nanostructured polyvinylferrocene /polypyrrole hybrid was fabricated via a co-deposition method as a result of the [pi]-[pi] stacking interactions between the aromatic pyrrole monomers and the metallocene moieties of polyvinylferrocene. The hybrid has a highly porous morphology with a significantly increased surface area compared to its bulk counterpart. / The synergistic effects between polyvinylferrocene and polypyrrole lead to enhanced ionic and electronic conductivity and, consequently, a higher specific capacitance as a supercapacitor electrode material. The second approach was a diffusion-controlled electrochemical method facilitated by the interactions between pyrrole monomers and the carbamate groups in CO₂-bound polyamines. As a result, a porous polypyrrole coating consisting of nanofibrous structures was synthesized and deposited on a carbon microfiber substrate. This composite material demonstrated enhanced electrochemical properties and adsorption capability towards aldehydes as a result of its porous morphology and high surface area. We later applied this composite material in achieving electrochemically modulated adsorption of polynucleotides. / The adsorption process was found to have a strong dependence on the oxidation states of the composite due to the electrostatic interactions between positively charged polypyrrole backbones and negatively charged phosphate groups in DNAs. / by Wenda Tian. / Ph. D. / Ph.D. Massachusetts Institute of Technology, Department of Chemical Engineering

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2018 / Cataloged from PDF version of thesis. Page 223 blank. / Includes bibliographical references. / This thesis focuses on the in-situ molecular engineering of chemical vapor deposition (CVD)-synthesized soft materials and device applications. High quality and large-scale synthesis of soft materials are the foundation of soft electronics. CVD approach has proved to be a low-cost and scalable technique to synthesize a wide variety of soft materials with desired properties. The first part (Chapter 2) will be dedicated to the record high electrical conductivity in CVD-grown poly(3,4-ethylenedioxythiophene) (PEDOT) thin films with controllable crystallization and morphology. The polymeric conducting thin film can be used as flexible and transparent electrodes in many electronic devices. Previously, the key problem limiting the electrical conductivity of PEDOT is the difficulty of maintaining a high carrier mobility simultaneously with a high carrier density in this polymer. / In order to solve this problem, we developed a facile CVD technology to effectively control the carrier mobility at high carrier density by controlling the crystallite configuration and morphology of PEDOT through molecular engineering. As a result, we successfully synthesized wafer-scale PEDOT thin films with a conductivity of 6259 S/cm, which is comparable to the widely used expensive indium tin oxide (ITO). This is the record high conductivity for large-scale thin film PEDOT. In addition, we also analyzed the polymeric system with a detailed theoretical model based on Boltzmann transport in order to understand the charge carrier transport mechanism. As a wafer-scale demonstration, we directly synthesized the highly conductive PEDOT thin film on a 4-inch silicon wafer and successfully fabricated PEDOT-Si diode arrays operating at 13.56 MHz, which can be used as high frequency rectifiers for RFID readers. / The second part (Chapter 3) will be dedicated to the enhancement of thermal properties of conjugated polymers synthesized using CVD technology. We developed a self-assembling CVD growth method for intrinsic poly(3- hexylthiophene) (P3HT) thin films and successfully achieved record high cross-plane thermal conductivity (>10x common polymers) in soft materials. Such a unique CVD growth mechanism results in an extended chain structure with good [pi]-[pi] stacking in P3HT, which significantly enhances the thermal transport within the CVD P3HT thin films. The third part (Chapter 4-7) will be about the fabrication of chemical sensors based on various nanostructured PEDOT and related copolymers, taking advantage of their ultrahigh surface-to-volume ratio. / by Xiaoxue Wang. / Ph. D. / Ph.D. Massachusetts Institute of Technology, Department of Chemical Engineering

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2018 / Cataloged from PDF version of thesis. Page 157 blank. Vita. / Includes bibliographical references (pages 137-153). / Core-shell nanostructures represent a promising and versatile design platform for enhancing the performance of noble metal catalysts while reducing the cost. Early transition metal carbides (TMCs) and nitrides (TMNs) have been identified as ideal core materials for supporting noble metal shells owing to their earth-abundance, thermal and chemical stability, electrical conductivity, and their ability to bind strongly to noble metals while still being immiscible with them. Unfortunately, the formation of surface oxides or carbon on TMCs and TMNs presents a difficult synthetic challenge for the deposition of atomically thin, uniform noble metal layers. Recent advances have enabled the synthesis of TMC core nanoparticles with noble metal shells (denoted as NM/TMC), although applicability toward TMN cores has not been previously demonstrated. Furthermore, the complete properties of these unique materials are still unknown. / This thesis conducts a detailed investigation of the synthesis, characterization, and catalytic performance of NM/TMC and NM/TMN core-shell nanoparticles to provide a comprehensive understanding of their material properties and the underlying phenomena. First, in-situ studies yielded insight into the mechanism behind the high temperature self-assembly of NM/TMC particles, indicating the presence of a metallic alloy phase preceding the formation of the core-shell structure upon insertion of carbon into the lattice. Next, the synthesis of NM/TMN nanoparticles was demonstrated via nitridation of a parent NM/TMC, and the structural and electronic properties of both core-shell materials were examined through in-situ X-ray absorption spectroscopy (XAS). The analysis revealed significant alterations to the electronic structure of the noble metal shell due to bonding interactions with the TMC and TMN cores, which led to weakened adsorbate binding energies. / Finally, the materials displayed improved performance for the oxygen reduction reaction (ORR), a critical challenge for fuel cell technologies. Notably, particles with complete, uniform shells exhibited unprecedented stability during electrochemical ageing at highly oxidizing conditions, highlighting the great potential of core-shell architectures with earth-abundant TMC and TMN cores for future ORR applications. Overall, this work will provide new opportunities toward the design of enhanced noble metal catalysts and enable further optimization of their performance. / by Aaron R. Garg. / Ph. D. / Ph.D. Massachusetts Institute of Technology, Department of Chemical Engineering

Acute pancreatitis is a sudden, severe inflammation of the pancreas which may eventually lead to life-threatening complications associated with digestive necrosis of the gland. Premature, intracellular activation of zymogens is believed to be responsible for the onset of acute pancreatitis; however, the underlying mechanisms remain unidentified. Alcohol is one of the most common risk factors in the development of this condition and may promote its deleterious effects by directly sensitizing the pancreatic acini to CCK, an important gastrointestinal peptide hormone and a digestive enzyme regulator which physiologically activates Ca2+ channels, thus serving an integral role in the physiological regulation of digestive enzyme secretion by pancreatic acinar cells. Nicotine exposure presents an accessory agonist and predisposing factor which may render the pancreas more susceptible to the injurious effects of alcohol-induced gland deficiency. It is important to evaluate the possible cumulative effect of these two high-risk factors in the pathophysiology of acute pancreatitis. The present study addresses the modulatory effects of ethanol and/or nicotine on CCK-evoked Ca2+ alterations and premature intracellular trypsin activation in murine pancreatic acinar cells. Our results indicate that alterations in Ca2+ signaling are often associated with pH modifications and may occasionally complement the conversion of trypsinogen to active trypsin in a time- and concentration dependent manner. We found corroborative evidence that ethanol affects cell signaling and sensitizes cells to the effects of CCK stimulation. Moreover, we found that the initiation of premature trypsin activity does not always succeed changes in [Ca2+]i. We also found evidence to support one existing pathophysiological theory which states that changes in [Ca2+]i are not a necessary indicator of premature trypsin activation. This initiating mechanism pathway may serve to complicate the development of therapeutic treatment and would suggest that other intrinsic factors may play a role in premature intracellular trypsin activation. These results not only indicate that CCK, ethanol and/or nicotine can trigger Ca2+ and pH responses, which may lead to autoactivation of digestive enzymes, but more importantly, may provide further evidence that Ca2+ is not the only initiating indicator of acute pancreatitis. Understanding the underlying cellular mechanism(s) by which ethanol and nicotine modulate pancreatic acinar cell activity and lead to premature intracellular activation of zymogens is paramount in design considerations which would identify pharmaceuticals effective in preventative and therapeutic treatment for acute pancreatitis. / A Dissertation submitted to the Department of Chemical and Biomedical Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Degree Awarded: Fall Semester, 2007. / Date of Defense: November 2, 2007. / Acinar, Trypsin / Includes bibliographical references. / Prescott Bryant Chase, Professor Directing Dissertation; Kenneth Brummel-Smith, Outside Committee Member; Egwu Kalu, Committee Member; Bruce R. Locke, Committee Member.

Receptor trafficking such as endocytosis may decrease the number of surface receptors and hence down-regulate receptor-mediated functions. Previous studies showed that dynamic endocytosis of N-methyl-d-aspartate receptor/channels (NMDARs) inhibits the gating of remaining surface NMDARs characterized by a reduction in channel open duration. Surprisingly, the blockade of Na+ influx prevents the gating down-regulation of remaining surface NMDARs induced by NMDAR endocytosis. More importantly, if this gating down-regulation is prevented, NMDA channel endocytosis produces no change in NMDA channel-mediated whole-cell and synaptic responses. Here, I report that blocking Na+ influx only during (R,S)-3,5-dihydroxyphenylglycine (DHPG) application, which induces NMDA channel endocytosis, could effectively block the down-regulation of NMDA channel-mediated excitatory postsynaptic currents (EPSCs) induced by NMDA channel endocytosis in adult CA1 neurons. This finding provided the first evidence confirming that the Na+ influx blockade during DHPG application sufficiently prevents DHPG-induced down-regulation of NMDA channel-mediated synaptic responses in CA1 neurons. / A Thesis submitted to the Department of Chemical & Biomedical Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Degree Awarded: Summer Semester, 2008. / Date of Defense: June 30, 2008. / DHPG, Synaptic Responses, NMDA Receptor / Includes bibliographical references. / Chi-Kai (Kevin) Chen, Professor Directing Thesis; Xian-Min Yu, Committee Member; Sachin Shanbhag, Committee Member.

The focus of this research is to study the effects of static magnetic fields used alone or in combination with radiation or anti-cancer drugs on mammalian cells. Recent work on the effects of static magnetic fields and electromagnetic fields on mammalian cells was reviewed in this dissertation. Controversial results about the magnetic effects on cell proliferation and cell death have been reported. Different magnetic field interaction sites on cells were proposed but the mechanisms and models need to be further confirmed. At our biomagnetic engineering lab low magnetic fields (less than 1 T) were produced by Neodymium Iron Boron magnets, high magnetic fields (less than 12 T) were produced by 500 M Hz high resolution NMR magnet system. Animal and human cell lines, normal and neoplastic, were exposed to magnetic fields. After various periods of exposure the magnetic effects on cell survival, cell death, cell proliferation, cell viability, cell DNA synthesis and cell metabolic activity were evaluated. The results showed that static magnetic fields have no significant effects on cell death and cell survival. However, cell proliferation and cell DNA synthesis were inhibited up to 20%. Within a short time of exposure, metabolic activity was improved in exposed group compared to control group. The combination effects of magnetic field and radiation, anti-cancer drugs were investigated to seek indirectly magnetic field targeting sites on cells and the potential application of magnetic field to cancer therapy. The results showed that magnetic field could slow down slightly the cell death process and help cells survive after radiation treatments. The efficacy of anti-cancer drugs on cancer cell in vitro in terms of dehydrogenase activity was improved or reduced by magnetic field depending on drug type. The results implied potential benefits for combined magnetic exposure and chemotherapy. The results demonstrate free radicals were involved in the process of magnetic field interaction with cells. / A Dissertation submitted to the Department of Chemical and Biomedical Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Degree Awarded: Summer Semester, 2005. / Date of Defense: July 8, 2005. / Includes bibliographical references. / Ching-Jen Chen, Professor Co-Directing Dissertation; Yousef Haik, Professor Co-Directing Dissertation; Kurt G. Holer, Outside Committee Member; Wei-Chun Chin, Committee Member; Soonjo Kwon, Committee Member.

Photoinduced structural change (PSC) is a fundamental excited-state dynamic process in chemical and biological systems, e.g. photoinduced flattening distortion of Cu(II) complexes1, PSCs of binuclear Pt (II) complexes2, 3. This process is highly dependent on the configuration of molecular excited-state potential energy surfaces (PESs). However, due to the lack of guidelines and approaches for designing excited-state PESs, precise manipulation of PSC processes is still very challenging. In this project, a series of rationally designed butterfly-like phosphorescent binuclear platinum complexes were synthesized with well-controlled PESs and tunable dual emissions at room temperature. We demonstrated our capability to manipulate PESs in two ways. First, we introduce the steric bulkiness effect of both cyclometalated ligands and pyrazolate bridging ligands to control the transition energy barrier of PSC process. Based on the Bell-Evans-Polanyi principle, which describe a chemical reaction between two energy minima on the first triplet excited-state PES, we reveal a simple method to engineer the dual emission of molecular systems by manipulating PES and therefore PSC to achieve desired molecular properties. Second, we synthetically control the electronic structure of the cyclometallating ligand and the steric bulkiness of the pyrazolate bridging ligand at the same time to realize the precise manipulation of the PESs. Color tuning of dual emission from blue/red, to green/red and red/deep red have been achieved for these phosphorescent molecular butterflies, which have two well-controlled energy minima on the PESs. The environmentally dependent photoluminescence of these molecular butterflies enabled their application as self-referenced luminescent viscosity sensor. / A Thesis submitted to the Department of Chemical and Biomedical Engineering in partial fulfillment of the Master of Science. / Spring Semester 2017. / April 14, 2017. / Includes bibliographical references. / Biwu Ma, Professor Directing Thesis; Daniel T. Hallinan, Jr., Committee Member; Subramanian Ramakrishnan, Committee Member.

Lignin can be an important source of synthetic commodity materials owing to its abundance in nature and low production cost. The current main usage of lignin, however, is very limited to cheap and poorly defined nonfunctional materials, because of undefined chemical structure of lignin and difficulties in chemical modification. This dissertation presents fundamental studies of chemical modifications for natural lignin, leading to advanced functional lignin-based polymers that contains covalently linked natural lignin and synthetic polymers (or other natural biopolymers). The presented graft copolymerization methods of lignin emphasis on 1) natural lignin modification to possess alkyne or alkene groups, 2) synthesis of well-defined functional polymer grafts, 3) covalent bond linkages between lignin and polymers, and 4) mechanical and thermal property studies for material applications. Based on the fundamental method to produce lignin-based polymers, a new lignin-based self-healing polymer, lignin-graft-poly(5-acetylaminopentyl acrylate) (lignin-graft-PAA) was synthesized. The natural lignin and PAA was covalently integrated by a copper catalyzed azide-alkyne cycloaddition using graft-onto method. Prior to the click reaction, lignin was modified to convert abundant hydroxyl groups to alkyne groups. The PAA was synthesized by reversible addition fragmentation-chain transfer (RAFT) polymerization that produces low molecular weight distribution polymers containing chemically active terminal, azide end groups. The synthesized lignin-graft-PAA showed excellent automatic self-healing function which was achieved by hydrogen bonding from the acetylamino groups in PAA. In this lignin-graft-PAA, lignin functioned to strengthen the mechanical strength. The mechanical properties of Young's modulus, energy, maximum strength, and ultimate elongation were enhanced with more lignin content. After using click chemistry as a graft method, a visible light induced thiol-ene reaction was applied to lignin polymeric modification. This is the first time that lignin is modified by Ru(bpy)3Cl2 photoredox catalyzed reaction. Among photoredox catalysts and UV initiators for thiol-ene reaction, including Eosin Y, Ru(bpy)3Cl2, and 2,2-Dimethoxy-2-phenylacetophenone, Ru(bpy)3Cl2 was found to be the most efficient on lignin modification. This modification was efficient between lignin and various thiol compounds, even with a polymer example, poly(ethylene glycol). This new modification method is an important synthetic tool for the further materials applications because of its features of low energy consumption, high efficiency, temporal and spatial control, and no need of special reaction facilities. Using this thiol-ene reaction, a new lignin-based shape memory polymer, crosslinked lignin-polycaprolactone (PCL) was synthesized. Lignin was modified from abundant hydroxyl groups to alkene groups to prepare for the thiol-ene reaction. PCL was synthesized by ring opening polymerization with a 4-arm architecture, which was designed for a dense crosslinking. The hydroxyl end groups from PCL was easily modified to thiol group through an esterification reaction. The alkene groups functioned lignin and thiol groups ended PCL were densely crosslinked by the thiol-ene reaction. The crosslinked lignin-PCL possessed an advanced shape memory function by the crosslinking structure with lignin as netpoints and PCL as switching segments. During the shape memory process, lignin netpoints hold the permanent structure and PCL switching segments allowed shape change. In this system, the role of lignin was a crosslinker additive. Moreover, the content of lignin crosslinker provided adjustment to melting temperature of the crosslinked lignin-PCL. More lignin content lowered the melting temperature by introducing defect to the PCL crystalline structure. Overall, lignin was integrated with polymers by precisely synthesis in this dissertation. The role of lignin was used as an important base polymer that occupies large portion, as well as a small amount additive. Both of the two roles can significantly change polymer properties to strengthen mechanical property and tune thermal property. The overall lignin-based polymer research in the dissertation may be very useful for advanced levels of material applications such as self-healing and shape memory polymers. / A Dissertation submitted to the Department of Chemical and Biomedical Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Fall Semester 2018. / November 8, 2018. / Includes bibliographical references. / Hoyong Chung, Professor Directing Dissertation; Joseph B. Schlenoff, University Representative; Daniel T. Hallinan, Jr., Committee Member; Jingjiao Guan, Committee Member.

As fuel costs continue to increase, novel methods to produce energy are becoming very important. Methods to generate hydrogen from organic material for utilization in fuel cells have been the source of much research over recent decades. One method to generate hydrogen is through microbial treatment of waste streams. The microbial treatment of wastes has great potential due to the mild conditions required to maintain biological systems, and other benefits such as removal of waste during the reaction process. The purpose of this research was to determine conditions in a bioreactor that would lead to the optimum rate of hydrogen production by manipulating process parameters. This was done by studying the affects of pH, temperature, organic loading rate, and hydraulic retention time in batch and continuous flow mixed bacterial culture reactors. The bacterial culture used in these experiments was able to generate the maximum amount of hydrogen from two different substrates in a reactor with a pH 5.2-5.7. The bacterial culture was able to convert substrates with the highest generation rate of hydrogen at 30 oC with a maximum of 0.25±0.01 mg H2/g COD h, while still being able to produce hydrogen at 40 oC with a maximum of 0.09±0.004 mg H2/g COD h. The optimum hydraulic retention time was found to be between 18 and 20 hours. Tests were conducted using loading rates between 55 and 450 mg COD/L and showed the maximum conversion of substrate occurred at 55 mg COD/L. These results indicate that hydrogen generation in a bacterial reactor will not be a sufficient method to generate power for further use, but could be feasible if used in conjunction with other sources of energy production. / A Thesis submitted to the Department of Chemical and Biomedical Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Degree Awarded: Fall Semester, 2006. / Date of Defense: November 8, 2006. / Mixed Culture, Biohydrogen, Acidogenesis / Includes bibliographical references. / Bruce R. Locke, Professor Directing Thesis; Teng Ma, Committee Member; Robert Reeves, Committee Member.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, February 2005. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references. / "September 2004." / The homogeneous-charge compression-ignition (HCCI) engine is a novel engine technology with the potential to substantially lower emissions from automotive sources. HCCI engines use lean-premixed combustion to achieve good fuel economy and low emissions of nitrogen-oxides and particulate matter. However, experimentally these engines have demonstrated a viable operating range that is too narrow for vehicular applications. Incomplete combustion or misfire can occur under fuel-lean conditions imposing a minimum load at which the engine can operate. At high loads, HCCI engines are often extremely loud and measured cylinder pressures show strong acoustic oscillations resembling those for a knocking sparkignited engine. The goal of this research was to understand the factors limiting the HCCI range of operability and propose ways of broadening that range. An engine simulation tool was developed to model the combustion process in the engine and predict HCCI knock and incomplete combustion. Predicting HCCI engine knock is particularly important because knock limits the maximum engine torque, and this limitation is a major obstacle to commercialization. A fundamentally-based criterion was developed and shown to give good predictions of the experimental knock limit. Our engine simulation tool was then used to explore the effect of various engine design parameters and operating conditions on the HCCI viable operating range. Performance maps, which show the response of the engine during a normal driving cycle, were constructed to compare these engine designs. The simulations showed that an acceptably broad operating range can be achieved by using a low compression ratio, low octane fuel, and moderate boost pressure. An explanation of why this choice of parameters gives a broad operating window is discussed. Our prediction of the HCCI knock limit is based on the autoignition theory of knock, which asserts that local overpressures in the engine are caused by extremely rapid chemical energy release. A competing theory asserts that knock is caused by the formation of detonation waves initiated at autoignition centers ('hot-spots') in the engine. No conclusive experimental evidence exists for the detonation theory, but many numerical simulations in the literature show that detonation formation is possible; however, some of the assumptions made in these simulations warrant re-examination. In particular, the effect of curvature on small (quasispherical) hot-spots has often been overlooked. We first examined the well-studied case of gasoline spark-ignited engine knock and observed that the size of the hot-spot needed to initiate a detonation is larger than the end-gas region where knock occurs. Subsequent studies of HCCI engine knock predicted that detonations would not form regardless of the hot-spot size because of the low energy content of fuel-lean mixtures typically used in these engines. Our predictions of the HCCI viable operating range were shown to be quite sensitive to details of the ignition chemistry. Therefore, an attempt was made to build an improved chemistry model for HCCI combustion using automatic mechanism-generation software developed in our research group. Extensions to the software were made to allow chemistry model construction for engine conditions. Model predictions for n-heptane/air combustion were compared to literature data from a jet-stirred reactor and rapid-compression machine. We conclude that automatic mechanism generation gives fair predictions without the tuning of rate parameters or other efforts to improve agreement. However, some tuning of the automatically-generated chemistry models is necessary to give the accurate predictions of HCCI combustion needed for our design calculations. / by Paul E. Yelvington. / Ph.D.