Date of Award

12-15-2022

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biomedical and Chemical Engineering

Advisor(s)

Hosein, Ian

Keywords

Nanoparticles, Phase behavior, Polymer nanocomposites, Polymerization kinetics, Raman spectroscopy, Surface science

Subject Categories

Chemical Engineering

Abstract

Establishing processing–structure relationships is central to materials science. In this work, we seek answers to whether morphology can be controlled during Light–Induced Self–Writing (LISW) in polymer composite materials, and if yes, how? LISW is based on the ability of light to undergo divergence–free propagation in photoreactive media due to photopolymerization–induced rise in refractive index of the medium. Notably, LISW in polymeric materials has found use predominantly for the fabrication of optical waveguides but has not been explored in polymer–inorganic mixtures. Using through–mask projection which creates a spatially periodic array of optical beams, this work extends LISW to nanoparticle–monomer mixtures to develop functional polymer composite materials. In a model photoreactive system containing Si nanoparticles dispersed in triacrylate monomer mixture undergoing LISW, it is found that the extent of nanoparticle dynamics can be controlled by controlling the incident light intensity used for photopolymerization. LISW at high incident light intensity revealed arrested nanoparticle dynamics, whereas this effect was not observed at low incident light intensity. By controlling the exposure time and exposure intensity, Si–decorated carbon pillars were fabricated and their application as Li–ion battery anodes was evaluated. Extension to TiO2 nanoparticle–containing mixtures resulted in a conformal nanoparticle top coating on underlying bump–like polymer structures. Correlation between nanoparticle weight fraction and exposure time with water contact angles revealed an optimum beyond which superhydrophobicity decreased. Exemplary processability and anti–wetting behavior of these materials was demonstrated. Additionally, Fe3O4–containing polymer pillars were fabricated for stimuli–responsive materials. Although polymer core–nanoparticle shell morphologies were observed at the μm–scale, stimuli response was not detected most likely owing to the rigidity of the polymer. Lastly, superhydrophobic powders were synthesized via rapid maskless photopolymerization of chemically dissimilar mixtures that form droplets. Final morphology was found to be marginally correlated to initial composition but not to the initial state of the mixtures.

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Open Access

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