CONTROLLED EVAPORATION DRIVEN SYNTHESIS AND APPLICATIONS OF ORDERED NANOPOROUS CERAMIC FILMS

This dissertation addresses the synthesis of oriented mesoporous ceramic films by evaporation induced self-assembly of surfactants and ceramic precursors in films dip coated from ethanol-rich sols. First, the kinetics of silica polycondensation in surfactant templated sol-gel films is studied both before and after deposition using infrared spectroscopy. These observations reveal an induction time (with minimal condensation rate) before curing begins in certain surfactant-templated silica films, which can be utilized to perform post-synthesis modification. This induction time is maximized at high humidity, and by long nonionic surfactant headgroups (rather than, for instance, a trimethylammonium headgroup). The second part of the dissertation addresses lattice Monte Carlo (MC) simulation of the effects of confinement on the 2D hexagonally close packed (HCP) phase formed by 60 vol% surfactant in a polar solvent. The effects of size and type of confining geometry (slit, cylindrical and spherical cavities) and of surface chemistry are simulated. The HCP mesophase orients orthogonal to chemically neutral surfaces which attract both head and tail of the surfactant equally. Novel mesophase geometries are simulated including radially oriented micelles, concentric helices, and concentric porous shells. Utilizing fundamental insights from the kinetics and MC studies, the third part of the dissertation describes the synthesis of silica films with orthogonally tilted HCP mesophase on chemically neutral surfaces. Crosslinking a random copolymer of polyethylene oxide (PEO)-polyproplyene oxide (PPO) on glass slides results in chemically neutral surfaces for the PEO-PPO-PEO triblock copolymer template (P123) used here. The orthogonal orientation of the HCP channels is confirmed using advanced x-ray scattering techniques and electron microscopy. The final part of the dissertation discusses applications of ceramic films with orthogonally tilted (ortho-) HCP mesophase. Silica membranes with ortho-HCP pores are prepared on porous alumina supports, and show permeability of ethanol orders of magnitude greater than films with parallel-oriented HCP channels. Size-selective filtration of gold nanoparticles confirms the absence of any nanoscale cracks in the membranes. For a second application, we prepare titania films with ortho-HCP mesopores. Careful crystallization of the films followed by spinning on an organic hole conducting polymer (P3HT) leads to active bulk heterojunction solar cells

Investigation of Design Space for Freeze-Drying: Use of Modeling for Primary Drying Segment of a Freeze-Drying Cycle

In this work, we explore the idea of using mathematical models to build design space for the primary drying portion of freeze-drying process. We start by defining design space for freeze-drying, followed by defining critical quality attributes and critical process parameters. Then using mathematical model, we build an insilico design space. Input parameters to the model (heat transfer coefficient and mass transfer resistance) were obtained from separate experimental runs. Two lyophilization runs are conducted to verify the model predictions. This confirmation of the model predictions with experimental results added to the confidence in the insilico design space. This simple step-by-step approach allowed us to minimize the number of experimental runs (preliminary runs to calculate heat transfer coefficient and mass transfer resistance plus two additional experimental runs to verify model predictions) required to define the design space. The established design space can then be used to understand the influence of critical process parameters on the critical quality attributes for all future cycles