The self-assembly of isotropic and anisotropic colloidal particles into higher-ordered structures has been of great interest recently due to the promise of creating metamaterials with novel macroscopic properties. The physicochemical properties of these metamaterials can be tailored to achieve composites with tunable functionalities. The formation of these metamaterials can be used as a pathway to emulating advanced biological systems. In particular, synthetically mimicking the surface of a moth’s eye, which consists of arrays of ellipsoidal protuberances, can be used as a strategy for fabricating antireflective coatings.
To enable this technology, it is necessary to design a synthesis scheme that produces micron-sized composite particles with tunable refractive index. In the future, the resulting composite microparticles can then undergo geometric and spatial modifications to form self-assemblies that have unique macroscopic material properties. This research work delineates a strategy of developing microparticles with a hybrid configuration that constitutes an inorganic and an organic part. The inorganic part comprises ~30 nm diameter titania (TiO2) nanoparticles, which are embedded within an organic polymer particle comprised of diethyl methylene malonate polymer [p(DEMM)]. Anionic polymerization is modified to controllably incorporate TiO2 nanoparticles into the polymer matrix. A design of experiments was identified and carried out to identify the major process variables that influence the final particle size. In particular, since DEMM polymerization may be initiated entirely by the presence of hydroxyl anions, pH was found to control the final overall particle diameter between 300 nm and 1 micrometer. The overall inorganic particle loading can be readily modified and is confirmed by thermogravimetric analysis, allowing for the desired macroscopic refractive index to be controlled. Light scattering, scanning electron microscopy and zeta potential analysis reveals that the colloidal stability of the hybrid microparticles is dependent on the ligand coating the inorganic constituent. In addition, this synthetic scheme is applied to different inorganic constituents that have interesting functionalities, such as fluorescent CdTe quantum dots, in order to show the methods versatility method to produce composite particles for a wide spectrum of applications. These initial investigations provide a the synthetic groundwork to evaluating the coating properties of the microparticles and their self-assembly into novel materials in the future.
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:masters_theses_2-2178 |
| Date | 20 October 2021 |
| Creators | Joshi, Shreyas |
| Publisher | ScholarWorks@UMass Amherst |
| Source Sets | University of Massachusetts, Amherst |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Masters Theses |
| Rights | http://creativecommons.org/licenses/by/4.0/ |
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