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Author ORCID Identifier

https://orcid.org/0000-0003-2724-1202

AccessType

Campus-Only Access for Five (5) Years

Document Type

dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Polymer Science and Engineering

Year Degree Awarded

2020

Month Degree Awarded

May

First Advisor

Ryan C. Hayward

Second Advisor

Todd Emrick

Subject Categories

Mechanics of Materials | Polymer Chemistry | Semiconductor and Optical Materials

Abstract

Synthetic advances to prepare novel nanoparticles (NPs) have opened exciting opportunities to develop polymer nanocomposite materials with important functionalities that benefit from the inherent properties of the host polymer matrix. To fully harness the potential of nanocomposites, the NP-polymer interface must be designed to control the extent of NP association, or degree of aggregation, in the polymer matrix. The first part of this thesis (Chapters 2 and 3) focuses on dispersion of perovskite NPs in polymers, including insulating and semiconducting versions. Polymer ligands were designed with ammonium bromide or zwitterionic pendent groups, which passivate the NPs and aid their dispersion in the host polymer. This strategy produced optically clear nanocomposite films that proved resistant to rapid degradation in the presence of polar solvents and even water. Nanocomposites composed of perovskite NPs and functional polymers, such as benzophenone-containing insulating polymers, or aromatic conjugated polymers, proved amenable to photolithographic processing and represent optoelectronic structures of interest for light-emitting displays. The second part of this thesis (Chapters 4 and 5) focuses on gold nanoparticle (Au NP)-embedded hydrogel nanocomposite disks (HNDs) and their macroscopic behavior at the air-water interface. Au NPs impart plasmonic photothermal heating to the host polymer, and therefore a route to trigger a mechanical response in temperature-sensitive matrices. Specifically, Au NPs were patterned in hydrogels by photoreduction methods, yielding nanocomposites that exhibit non-uniform heating when illuminated. This strategy enabled light-induced differential swelling and wrinkling of hydrogel nanocomposite films at the air-water interface, providing a versatile route to control interfacial capillary forces and programmed materials assembly. Sustained active motion of HNDs under light-induced Marangoni confinement was also studied. Non-uniform temperature distribution around the HNDs, induced by photothermal heating, produced non-uniform surface tension and resultant motion at the air-water interface. A rational design of an optical trapping boundary enabled sustained oscillatory motion of HNDs, as well as thermally coupled multi-disk motion. By combining the illumination patterns and spatially distributed Au NPs in HNDs, more complex behaviors were discovered, such as coupled HND rotation and translation. This result provides a versatile experimental platform for studying active particles and their coupled motions as well as possible pathways towards realization of micro-robots that function at air-fluid interfaces.

DOI

https://doi.org/10.7275/17656295

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