Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1986. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 211-218. / by Michael Jeffrey Hegarty Snow. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2005. / Includes bibliographical references. / Pulsed plasma enhanced chemical vapor deposition has produced organosilicon thin films with the potential use as low dielectric constant interconnect materials in microelectronic circuits. Both diethylsilane and octamethylcyclotetrasiloxane precursors were used, with oxygen and hydrogen peroxides oxidants respectively, to deposit low-k organosilicon films. FTIR, nanoindentation, ellipsometry, and dielectric constant measurements were demonstrated as a valuable film characterization tools to understand structure-property-processing fundamentals by quantifying structural bonding environments and relating those to the film properties. Nanocomposites were also produced using two novel techniques. First, crystal colloidal templates of polystyrene nanospheres were fabricated using evaporation-induced self-assembly. OSG was then deposited throughout the templates to create composite materials. Subsequently the polystyrene was removed upon thermal annealing to create highly porous OSG thin films. Second, ultrasonic atomization was used to deliver particles into a vacuum chamber during plasma-enhanced CVD of the organosilicon matrix to create composite thin films using an all-CVD technique. This process could extend CVD to applications currently only possible using wet processing techniques or multi-step processing. / by April Denise Ross. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1987. / Bibliography: leaves 136-142. / by Steven D. Perry. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2005. / Includes bibliographical references (p. 173-182). / The oxidation of cyclohexadienyl radical (c-C₆H₇) and similar resonantly stabilized radicals are important in an astonishing array of processes in nature. Cyclohexadienyl radical has been postulated to be significant in a variety of processes that involve the atmospheric formation of benzene. In biology, there are specific enzymes that promote the formation of benzene-like intermediates from cyclohexadienyl radicals, called cyclohexadienyl dehydratases. In combustion processes, cyclohexadienyl radical is a possible link to the formation of soot and other large polyaromatic hydrocarbons (PAH's). Thus, the cyclohexadienyl radical moiety is important in many chemical processes, and its detailed study is of interest in many areas. In this work, cyclohexadienyl radical is studied both computationally and experimentally in the liquid and gas phases. The cyclohexadienyl radical is created using laser-flash photolysis. The UV absorption bands of the radical are probed and it's relative concentration over time measured in non-polar solvents in both the presence and absence of oxygen. Several analytical and numerical models of the chemistry were constructed to explain a puzzling discrepancy in the reported liquid and gas phase reaction rates. / (cont.) The models and data developed were then used in testing new software for finding the global optimum of dynamic systems. Optimized parameters for several key reaction pathways are reported, as well as a detailed description of the procedure. Finally, c-C₆H₇ was studied in the gas phase using an ultra-fast laser system. Preliminary results from those experiments are reported, as well as recommendations for future work. / by James Wagner Taylor. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, February 2007. / Includes bibliographical references. / In the initial investigation of this thesis, Fick's second law of diffusion was modified to describe both the transient, and the steady-state, transdermal transport of hydrophilic permeants through unbranched, aqueous pore channels. This new transport model, combined with dual radiolabeled diffusion experiments, was then used to separately evaluate how the porosity, the tortuosity, and the hindrance factor of the aqueous pore channels that exist in the skin varied as the extent of skin perturbation due to simultaneous treatment of the skin with low-frequency ultrasound (US) and a chemical enhancer, the surfactant sodium lauryl sulfate (SLS), and as the radius of the hydrophilic permeant delivered across the skin, were increased. This investigation revealed that the values of the hindrance factor and of the tortuosity decreased as the radius of the hydrophilic permeant increased, and that the value of the porosity of the aqueous pore channels increased as the extent of skin perturbation due to the application of US increased. This last result suggested that low-frequency US primarily enhances the transport of hydrophilic permeants by increasing the fraction of the skin surface occupied by the aqueous pore channels. / (cont.) This modeling approach was next applied to the passive delivery of hydrophobic permeants through the branched pathways located in the intercellular lipid bilayer domain of untreated stratum corneum (SC), the outermost layer of the skin. The existence of these branched pathways led to the development of a new theoretical model, the Two-Tortuosity Model, which requires two tortuosity factors to account for: 1) the effective diffusion path length, and 2) the total volume of the branched, intercellular transport pathways, both of which may be evaluated from known values of the SC structure. After validating the Two-Tortuosity model with simulated SC diffusion experiments in FEMLAB (a finite element software package), the vehicle-bilayer partition coefficient, Kb, and the lipid bilayer diffusion coefficient, Db, in untreated human SC were evaluated using this new model for two hydrophobic permeants, naphthol (Kb = 233 + 44, Db = 1.6*10-7 + 0.3*10-7 cm2/s) and testosterone (Kb = 100 + 14, Db = 1.8*10-8 + 0.2*10-8 cm2/s). This investigation demonstrated that the new proposed method to evaluate Kb and Db is more direct than previous methods, in which SC permeation experiments were combined with octanol-water partition experiments, or with SC solute release experiments, to evaluate Kb and Db. / (cont.) Previous studies on ultrasound-mediated transdermal drug delivery had hypothesized that the discrete regions which form on the surface of skin treated with low-frequency US in the presence of a colored permeant are regions of high permeability. To test this hypothesis, full-thickness pig skin was treated simultaneously with low-frequency US and SLS in the presence of a hydrophilic fluorescent permeant, sulforhodamine B (SRB), which was used to observe the location of the hypothesized localized transport regions (LTRs) and of the surrounding regions of US-treated skin (the non-LTRs). After US-pretreatment, diffusion masking experiments, a novel experimental method in which hydrophobic vacuum grease was selectively applied to the skin surface, demonstrated that the permeability of calcein, another hydrophilic fluorescent permeant, in the LTRs was -80-fold greater than in the non-LTRs. Furthermore, measurements of the skin electrical resistivity in both the LTRs and the non-LTRs revealed significant decreases relative to the skin electrical resistivity in untreated skin (-5000-fold and -170-fold, respectively), suggesting that two levels of significant structural perturbation exist in skin treated simultaneously with ultrasound and SLS. / (cont.) Finally, an analysis of the porosity-to-tortuosity ratio values suggested that transcellular transdermal transport pathways exist within the LTRs. To confirm the results of the previous investigation, the transdermal delivery of SRB and of rhodamine B hexyl ester (RBHE), a fluorescent hydrophobic permeant, in skin treated with low-frequency ultrasound (US) and/or a chemical enhancer (SLS) relative to untreated skin (the control) was analyzed with dual-channel two-photon microscopy (TPM). An analysis of the average fluorescence intensity profiles as a function of skin depth, obtained from the TPM images, revealed that SRB and RBHE penetrated beyond the stratum corneum and into the viable epidermis only in the LTRs of US-treated and of US/SLS-treated skin. Further analysis of the average fluorescence intensity profiles and of the enhancements in the vehicle-skin partition coefficient, the intensity gradient, and the effective diffusion path length confirmed that a chemical enhancer was required in the coupling medium during US-treatment to obtain two significant levels of increased penetration of SRB and RBHE into the skin. / (cont.) Finally, by comparing the heights and the widths of the fluorescence intensity peaks obtained from the dual-channel TPM images, the existence of transcellular pathways was confirmed in the LTRs of US-treated and of US/SLS-treated skin for SRB and RBHE, as well as in SLS-treated skin for SRB. In the final investigation of this thesis, the differences in the hindrance factor, the porosity, and the tortuosity of the aqueous pore channels located in the LTRs and in the non-LTRs were evaluated for the delivery of four hydrophilic permeants (urea, mannitol, raffinose, and inulin) using the transport model developed in the initial investigation of this thesis combined with dual radiolabeled diffusion masking experiments. In this analysis, three different idealized cases were examined. In the first case, where the porosity and the tortuosity were assumed to be independent of the permeant radius, the hindrance factor, and, therefore, the average pore radius, was found to be statistically larger in the LTRs than in the non-LTRs. In the second case, where a distribution of pore radii was assumed to exist in the skin, no meaningful results could be obtained due to the large variation in the shape of the distribution of pore radii used in the analysis. / (cont.) In the final case, where infinitely large aqueous pores were assumed to exist in the skin, the value of the porosity of the LTRs was found to be 3- to 8-fold larger than that of the non-LTRs, while there little difference was found in the values of the tortuosity of the LTRs and of the non-LTRs. / by Joseph Kushner, IV. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1997. / Includes bibliographical references (p. 57-58). / by Dimitrios M. Stratikopoulos. / M.S.

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

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references. / This thesis discusses my work to design, build, troubleshoot, and utilize a novel experimental apparatus that is capable of quantitatively measuring the concentrations of reacting gas-phase species and their reactive intermediates with sufficient time-resolution and sensitivity to determine both the kinetics and the product distributions of these systems. The apparatus uses laser absorption spectrometry to probe a radical of interest and thus measure its transient concentration quasi-continuously to precisely determine the kinetics of the reaction. At the same time, the apparatus samples the reactive mixture at various reaction times after the start of reaction to determine the time-resolved product distribution of the chemical system. This combination of techniques was used to study the reactions of vinyl radicals with alkenes, which are important reactions in incipient soot formation in combustion systems. Revised chemical kinetic rate coefficients and, for the first time, temperature- and pressure-dependent product branching fractions were experimentally measured for these reactions. In addition, a new potential energy surface for the vinyl + ethene reaction was calculated using state-of-the-art F12 quantum chemistry calculations, and the master equation for this reactive system was solved using various methods to determine the temperature- and pressure-dependent rate coefficients and product branching fractions. / by Joshua E. Middaugh. / Ph. D.

Thesis (Sc.D.) Massachusetts Institute of Technology. Dept. of Chemical Engineering, 1948. / Vita. Appendix contains numerous pamphlets. / Includes bibliographies. / by Arthur Spragens Collins. / Sc.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1937. / Includes bibliographical references (leaves 53-54). / by Herbert M. Borden and Walter Squires, Jr. / M.S.