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Doctor of Philosophy (PhD)
Polymer Science and Engineering
Year Degree Awarded
Month Degree Awarded
James J. Watkins
H. Henning Winter
Ceramic Materials | Materials Science and Engineering | Nanoscience and Nanotechnology | Polymer and Organic Materials | Polymer Chemistry | Polymer Science | Semiconductor and Optical Materials
The research in this dissertation is categorized into two parts. The first part is focused on investigation of order-to-disorder transitions (ODT) in nanocomposites of an amphiphilic block copolymer containing various hydrogen-bonded additives, and fabrication of novel mesoporous silica based materials by utilizing such nanocomposites as templates.
Disordered Pluronic®, poly(ethylene oxide) (PEO)−poly(propylene oxide) (PPO)−PEO triblock copolymer upon blending with small molecule additives containing hydrogen-bond-donating functional groups (carboxyl or hydroxyl) result into ordered nanoscale morphologies by preferentially interacting with the hydrophilic PEO chains in the Pluronic®. The dependence of ODT-temperature in these novel Pluronic®/small-molecule-additive complexes on composition, number and type of functional groups on the additive, and the phase behavior of complexes, is explored using rheology.
High loadings of metallic nanoparticles can be achieved in the hydrophilic PEO domain of the Pluronic® by taking the advantage of hydrogen bonding interactions. By utilizing Pluronic®/nanoparticle composites as templates, well-ordered mesoporous/nanoparticle composites (with up to 15 wt% nanoparticles) are fabricated using supercritical carbon dioxide (scCO2)assisted infusion and phase selective condensation of a silica-precursor within the PEO phase of the template. Well-ordered mesoporous silica with such high concentrations of uniformly distributed nanoparticles are advantageous in catalysis, but are elusive using synthetic routes explored in the literature.
Hierarchically porous silica monoliths with high surface area mesopores interconnected through macropores are fabricated using scCO2 assisted phase selective infusion and condensation of a silica-precursor in a Pluronic®/small-molecule-additive template coated on a macroporous template. The surface area of mesoporous silica prepared by the scCO2 infusion process is reported for the first time using nitrogen physisorption experiments. A systematic study of various parameters pertaining to the scCO2 infusion process on the final morphology and surface area of the mesoporous silica is carried out.
In the second part, a soft lithography technique is explored to fabricate nanostructures of inorganic oxides, for example ITO and TiO2,using inks containing crystalline nanoparticles. The technique is evaluated based on its ability to imprint dimensionally stable high-aspect-ratio nanostructures. Rapid imprinting, residual-layer free imprinting and imprinting of sub-200-nm structures is also demonstrated. A layer-by-layer imprinting strategy is developed to realize all-solution processable 3D inorganic nanostructures.
Kothari, Rohit, "(I) Polymer Nanocomposites: Rheology and Processing for Mesoporous Materials and (II) Nanopatterning of Metal Oxides Using Soft Lithography" (2016). Doctoral Dissertations. 584.