Date of Award

Fall 2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical and Environmental Engineering (ENAS)

First Advisor

Zhong, Mingjiang

Abstract

Bottom-up fabrication of hierarchically structured materials with precisely controlled molecular arrangements is desirable for numerous advanced applications, ranging from separations, microelectronics, photonics, to energy storage. However, the inability to synthesize hierarchical structures with independently tunable lattices across multiple length scales limits the discovery of next-generation multifunctional materials. This thesis aims to develop a molecular self-assembly strategy based on multicomponent mixed-graft block copolymers (mGBCPs) to fabricate nanostructured materials with a variety of phase-in-phase hierarchical morphologies that combine nano- and mesoscale features. In this thesis, mGBCPs containing sequence-defined side chains can phase-separate to form ordered hierarchical structures with intramolecularly defined interfaces and independently tailored lattices. The proof-of-principle self-assembly study was carried out using mGBCPs synthesized from block-copolymerization of a branched A/B-macromonomer and a linear C-macromonomer. Our findings demonstrated that the characteristic sizes of the superstructure and substructure in the hierarchically assembled nanostructures were governed by the backbone and side chain lengths, respectively. Subsequently, the structural complexity of the mGBCPs was increased by introducing two distinct branched macromonomers into one mGBCP molecule, affording alternatingly arranged lamellar and cylindrical substructures. We developed a theoretical model to quantitatively elucidate the molecular packing and related thermodynamics in the hetero-substructure containing system. These novel multicomponent hierarchical nanostructures were then scalably produced through a simplified synthetic route based only on a small set of linear macromonomers. Lastly, we leveraged our rationally designed mGBCPs to develop hierarchically structured materials with macroscopic long-range ordering. Rapid shear alignment at ambient temperature was employed to enable orientation control of the substructure lamellae or cylinders perpendicular to the shear plane.

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