Dissertations, Theses, and Capstone Projects

Date of Degree

9-2020

Document Type

Dissertation

Degree Name

Ph.D.

Program

Chemistry

Advisor

Michal Kruk

Advisor

Nan-Loh Yang

Committee Members

Mark Kobrak

Subject Categories

Chemistry | Materials Chemistry | Polymer Chemistry

Keywords

mesoporous, nanomaterials, SBA-15, silicas, nanotubes

Abstract

The original research described herein concerns the synthesis of mesoporous silicas through a surfactant-templating method. The approach taken involved the use of a mixed surfactant system of two poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) surfactants, with one of the copolymers containing a much larger percentage of hydrophobic (PPO) blocks than the employed co-surfactant. Systematic adjustments of experimental parameters initially enabled the preparation of 2-D hexagonally ordered mesoporous silicas (SBA-15) of uncommonly large pore diameter at ambient temperature. Comparable silica was synthesized with and without temperature control. Additional adjustments to experimental parameters, including reduction of the relative amount of framework precursor used in the synthesis, led to the synthesis of counterpart single-micelle templated silica nanotubes of record pore size at ambient temperature. The pores sizes of the silica nanotubes were able to be tuned by adjustment of the volume of swelling agent added during synthesis, and synthesis was possible without temperature control and at several fixed temperatures around ambient temperature. A remarkable development in the described study of the mixed surfactant system was the discovery of a facile method for production of hollow helical silica structures with large inner pore spaces at considerable scale. These structures have only been attainable in the past at high expense, and presumably in limited quantities.

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