Nanostructure Formation Of Inorganic Materials From The Self-Assembly Of Highly Amphiphilic Block Copolymers
Song, Ju Ho
High performance catalysts or energy devices such as solar cells and batteries which involve reactions and transport problems require nanostructured functional materials that are highly ordered mesoporous and crystalline materials. The self-assembly based structure direction of functional inorganic materials by block copolymers (BCPs) is a promising route because it combines mesoporosity at the 2-50 nm length scale, high surface areas and full control over morphology. This work explored solubility design guidelines that facilitate the coassembly of titania and poly(isoprene-b-ethylene oxide) (PI-b-PEO) which is a highly amphiphilic block copolymer. This approach enabled the fabrication of highly ordered crystalline titania. The pore size control of mesoporous crystalline titania was also accomplished by applying different molecular weight PI-bPEOs, and the highly ordered titania with the largest cylindrical pores (>30 nm) was reported without the use of pore-expanders. Nanostructured titania membranes were developed for water purification applications based on the knowledge from the previous part because inorganic membranes have superior thermal and chemical stabilities over polymer membranes. The mesoporous titania membranes with different pore size were successfully fabricated on porous disc substrates from both large and small molar mass PI-b-PEOs and presented an excellent molecular weight cut-off performances with high permeability, which would provide a huge potential to be applied in many ultrafiltration areas due to its self-cleaning characteristics from the photocatalytic activity. Finally, an ABC triblock terpolymer system was studied as an extension of the BCP self-assembly based structure direction of inorganic materials because these terpolymers allow wider composition windows for ordered network structures that have advantages such as 3-D connectivity and enhanced mechanical properties. In this work, the ternary morphology map of PI-b-PS-b-PEO and aluminisolicate sols was successfully constructed, which reveals 10 distinct morphologies along with particularly wide composition windows (2-13 vol%) for ordered network morphologies. This morphology map could be used as a model to predict the structure direction of other functional inorganic materials and a highly ordered network titania composite with core-shell double gyroid structure (cs-GD) was demonstrated as an example.
block copolymer self-assembly; inorganic materials; nanostructures
Wiesner, Ulrich B.
Disalvo, Francis J; Joo, Yong L.
Ph. D., Chemical Engineering
Doctor of Philosophy
dissertation or thesis