Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2003. / Includes bibliographical references. / This work applies the processing technique of layer-by-layer (LBL) assembly to the creation and development of new electrochemically active materials. Elements of the thin-film electrochromic cell were chosen as a particular focus for LBL fabrication. Layer-by-layer assembly is the ideal processing tool to tailor the electrochemical systems within electrochromic cells because modulating processing conditions can greatly impact the nanoscale composition and morphology of the resultant films. For the first time, this control was used to: 1) intelligently design electrochromic LBL assembled composite films that facilitated ion motion for faster switching and exhibited enhanced or shifted coloration, 2) combine multiple electrochromic materials into novel LBL assembled composites with even higher contrast, faster switching, and multiple colored states, and finally 3) develop and optimize several LBL assembled polymer electrolyte films that display high ionic conductivity and sound mechanical integrity. Electrochromic cell elements were chosen not only for their undeveloped commercial potential, but also because they incorporate multifunctional material systems with alternative applications. Studies of LBL fabrication and the operation of electrochromic cells provide insight into intermolecular interactions, internal and external film interfaces, thin film electrochemistry, and charged species mobility in polymer solids. First investigated was the capability of LBL assembly to alter the properties of electrochromic films by varying molecular blending. / (cont.) The electrochromophores for this investigation were appropriated from all corners of the materials spectrum, including discrete electrochromic polymers, conjugated polymers, soft colloidal suspensions, and inorganic particle dispersions. In each system, the influence of assembly conditions and film composition was elucidated; in particular systems the hydrophobicity, acidity, and morphology of the films were found to impact the electrochemistry and optical character of the films, providing a means to modulate these properties by directing LBL assembly design choices. Because of the high uniformity and thickness control allowed by LBL assembly, the contrast and switching performance of all LBL assembled electrochromic films were in general superior to those of films containing the same electrochromophores fabricated by other methods. One particularly promising system involved novel LBL assembled films containing the same electrochromophores fabricated by other methods. One particularly promising system involved novel LBL assembled films containing electrochromic metal hexacyanoferrate nanocrystals of the Prussian blue family. These films displayed fast and deep coloration; synthetic nanocrystal variation extended absorbance over a broad spectral range so that these inorganic/polymer composite films could potentially be considered as elements in a full-color switchable CMYK display. The power of the LBL assembly technique was leveraged further with the successful fabrication of "dual electrochrome" electrodes ... / by Dean M. DeLongchamp. / Ph.D.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1998. / Includes bibliographical references (leaves 214-218). / by Matthew Michael DiPippo. / Sc.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1999. / Includes bibliographical references. / The objectives of this project are to understand the reaction mechanisms for oxide etching by both HF/H2 0 and HF/alcohol processes and to develop a vapor phase HF cleaning process to remove metallic contamination and native oxide on a silicon surface. Although the HF vapor process has been studied intensively for past several decades, the commercial application has not been very successful due to the unknown nature of the process. This study, performed at MIT, has emphasized on finding possible applications to the semiconductor industry as a replacement to the aqueous phase cleaning processes. The ultimate purpose of this project is to demonstrate feasibility of the HF vapor process for a vacuum compatible and clustered cleaning process. In this study, the etching experiments were carried out in a stainless steel vacuum chamber connected to a vacuum wafer transfer system. Samples were introduced through a load lock chamber and transferred to the HF vapor reaction chamber. The base pressure of the system was maintained under 10-7 Torr. The system can handle sample sizes between 1 cm square and 10 cm diameter silicon wafers. The etching rates were measured by an in situ ellipsometer installed on the HF vapor reactor. Ellipsometric measurements suggest that oxide etching can occur without a condensed layer or with a condensed layer on the oxide surface. The etching rates of oxide in the condensed regime were very high (3,000-12,000 A/min) compared to the gas phase regime (0-300 A/min). The etching regime in which a condensed layer is formed is a function of not only the partial pressures of HF and H 20 in the feed gas, but also a function of the mass transport of the products from the sample in the gas phase. We have categorized two different etching regimes: the gas phase regime and the condensed phase regime. In the gas phase etching regime, reactant molecules are adsorbed on the oxide surface in sub-monolayer, monolayer, or multilayer films. In the multilayer adsorption regime, the etching rate is usually low (typically 0-400 A/min) and is linearly proportional to the partial pressure of HF and H20. The etching rate in this regime is greatly affected by the temperature of the substrate. The mass transfer rate limits the etch rate of oxide in the multilayer adsorption regime. In the submonolayer or monolayer adsorption regime the etching rate is described by Langmuir- Hinshelwood kinetics. The etching rate is governed by surface kinetics in this regime. Advantages of this etching regime are: 1) smoother etched surface, 2) low selectivity to TEOS, 3) haze-free etched surface, 4) no metal attack, 5) perfect removal of native oxide, and 6) vacuum compatible process. The HF vapor process in this regime is an ideal process for contact cleaning and polymer removal after metal or via etching. Electrostatic charge on the wafer surface affects the etching reaction significantly in the non-condensed regimes. A positively charged surface enhanced the etching reaction in the submonolayer and monolayer etching regimes. Direct ionization of HF on the oxide surface is responsible for the enhancement in this regime. A negatively charged surface mainly enhanced the etching in the multilayer regime. A thicker multilayer, induced by the formation of fluorosilicate, is responsible for the etching enhancement in this regime. We have demonstrated a successful removal of sodium from both oxide and silicon surfaces using HF/H2 0, HF/IPA, and HF/H20/SiF4 processes in reduced pressure operation. All experiments were performed in a vacuum environment and in-situ XPS was used to measure the surface concentration of sodium. The sodium contamination on oxide surface was successfully removed by both HF/H 20 and HF/IPA processes. The HF/H 20 process could not remove all of sodium contamination on a silicon surface. The addition of SiF4 in the HF/H 20 process greatly enhances the cleaning effect, reducing Na contamination below the detection limit of our XPS, even on a silicon surface. Based on our study, we have reported a true gas phase and vacuum compatible HF vapor process, operated in the monolayer adsorption regime at elevated temperature. A successful removal of RIE residue was performed with a combined cleaning procedure of HF vapor and ashing process. This combined process is a perfect dry cleaning process for contact cleaning method. This process sequence is ideal for a vacuum cluster configuration in which a single wafer is processed at a time and is not exposed in the ambient. / by Yong-Pil Han. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 152-160). / This thesis work focuses on designing thin polyelectrolyte multilayer (PEM) films via layer-bylayer (LbL) deposition technique with the ability to kill pathogenic bacteria and inactivate human viruses, especially the influenza (flu) virus on contact. This work builds on four years of research at the Institute for Soldier Nanotechnologies (ISN) focusing on creating new, nonleaching microbicidal material; this film is envisioned to be used as permanent surface coatings for weapons, equipments, uniforms, personal items, etc. because a small reduction in the rate of infection will greatly enhance the readiness and performance of soldiers and other military personnel. Extending this application to everyday life, commonly handled objects such as doorknobs, computer keyboards, and touch screens can also be made sterile by coating them with these highly effective microbicidal PEM films. These films can also be used to prevent infections and long-term bacterial biofilms on implant surfaces. The ultimate aim of this thesis work is to create a broadly applicable multifunctional platform film technology that will satisfy various thin film surface coating applications; this film will impart a surface with long term antimicrobial / antifouling functionality via a permanent microbicidal base, and controlled delivery of a therapeutic agent via a hydrolytically degradable top film as needed. Efforts were focused on maximizing and understanding the factors that influence the microbicidal / antifouling property of the film; thus far, we successfully designed a set of contact-killing ionically cross-linked polymeric thin films; a hydrophobic polycation, linear NNdodecyl, methyl- poly(ethylenimine) (DMLPEI) with microbicidal activity was layered with a hydrophilic polyanion, such as poly(acrylic acid) (PAA), to create LbL films highly effective against Escherichia coli and Staphylococcus aureus (Gram negative and positive bacteria, respectively), as well as the influenza A/WSN (H1N1) virus. The microbicidal film was also demonstrated to significantly resist adsorption of protein from blood plasma relative to an uncoated substrate. By generating PEM films assembled with the hydrophobic N-alkylated poly(ethylenimine) and the hydrophilic poly(acrylic acid), an ultrathin film that exhibited antifouling and antimicrobial properties was created. Results showed that a fine balance of hydrophobicity and hydrophilicity on the surface of the films was needed to create molecularlevel heterogeneities unfavorable to protein adsorption; due to the contrasting nature of the polymer making up the film, nanoscale segregation of the polymer segments into hydrophobic and hydrophilic moieties could occur on the surface. We then moved on to design a dual functional LbL film construct combining the permanent microbicidal / antifouling base film with a hydrolytically degradable PEM top film offering controlled and localized delivery of therapeutics (e.g. antibiotic, anti-inflammatory drug, etc.). When the degradable top film is completely eroded, the surface will be left with the permanent microbicidal film for long-term prevention of fouling by biomolecules and microorganisms (e.g., proteins and bacteria). / by Sze Yinn (Jessie) Wong. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1998. / Includes bibliographical references (v. 2, leaves [338]-355). / by Philip A. Marrone. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2012. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / "June 2012." Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (p. 100-108). / Photo-responsive liquid crystal polymers (LCP) which contain azobenzene moieties have gained interest for their ability to change properties by merely irradiating them with the correct wavelength of light in the appropriate temperature range. Furthermore, they have been crosslinked for elasticity and to translate this property change into photo-mechanical actuation, such as contraction, expansion, bending, or oscillation. However, a major drawback and hindrance to their actual use as actuators has been their need for elevated temperatures and their slow responses at room temperature. The work described in this thesis addresses this problem, and its solution has an impact on the field of functional elastomers in general. To produce a fast photo-response at room temperature, a new photo-responsive azobenzene nematic side chain (SC) LC polysiloxane was developed, characterized, and demonstrated to respond significantly, and reversibly from 0-50°C, which is the ambient temperature range in which we live, through its photo-induced nematic to isotropic transition. In particular, its nematic phase almost totally disappeared in 35 s, and its modulus decreased up to 35% in about 10 s. To turn this photo-response into photo-actuation, polystyrene (PS) end blocks were added to the poly(vinylmethylsiloxane) (PVMS) to produce PS-b-PVMS-b-PS, which is important in and of itself because the PVMS has a very low Tg and a functionalizable backbone and the PS end blocks make the material a thermoplastic elastomer. After attachment of the azobenzene LC, the resulting photo-responsive thermoplastic elastomer reversibly contracted 3.3% against 25.7 kPa of stress in about 6 s. / by Michael Thomas Petr. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1985. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 420-427. / by Pablo G. Debenedetti. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1997. / Includes bibliographical references. / by Andrew Soctt Lawing. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2002. / Includes bibliographical references (p. 38-39). / Micro-contact printing has emerged as a promising new technique for patterning micron scale features with a wide variety of materials. Most of the materials examined have been small, reactive molecules patterned on surfaces they are chemically attracted to, like thiols on metals or silanes on glass and metal oxides. Our group has introduced a new approach to surface patterning by using polymers to pattern polymeric surfaces. To further expand the options of charged surfaces, we decided to study strong polyelectrolytes, and their optimal stamping conditions when printed onto polymer platforms, particularly multilayer surfaces. The size of the features that could be produced was also examined. The success of printing strong polyelectrolytes onto polymer layers depends on the properties of the ink solution as well as the properties of the polyelectrolyte used. SPS is best printed from a concentrated aqueous solution including a large amount of salt. PDAC can be stamped from either concentrated ethanol based inks or from a dilute aqueous one. The more concentrated ink produces prints faster and more reliably, but causes more damage to the stamps used. PDAC can also be used to print nano-scale features, using a concentrated aqueous ink. / by Shoshana Ruth Gourdin. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1955. / Vita. / Includes bibliographical references (leaves 216-217). / by Edward S. Cohen. / M.S.