Polymer-patchy nanoparticles synthesis and self-assembly into reconfigurable networks

Kim, Ahyoung

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https://hdl.handle.net/2142/115923 Copy

Description

Title

Polymer-patchy nanoparticles synthesis and self-assembly into reconfigurable networks

Author(s)

Kim, Ahyoung

Issue Date

2022-07-15

Director of Research (if dissertation) or Advisor (if thesis)

Chen, Qian

Doctoral Committee Chair(s)

Chen, Qian

Committee Member(s)

• Schweizer, Kenneth S.
• Murphy, Catherine J.
• Shim, Moonsub

Department of Study

Materials Science & Engineerng

Discipline

Materials Science & Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

polymer, nanoparticle, patchy particle, patchy nanoparticle, self-assembly

Abstract

Living organisms assemble vital materials with high energy efficiency and structural complexity, simply by utilizing the surface “patches” and abundant thermal energy. In particular at the nanoscale, biomolecules such as proteins and viral particles have patches of distinct domains of surface chemistry, which encode rich phase behaviors and functions. Inspired by such, the goal of my Ph.D. studies is to emulate these two facets of biomolecules—nanoscale patchiness and encoded assembly behaviors—in colloidal nanoparticles (NPs), to understand fundamental self-organization rules at the nanoscale and to construct reconfigurable, open networks and lattices that are hard to achieve with conventional NPs with the homogeneous surface. Open lattices such as Kagome and diamond lattices that can interact in novel ways with incident light and have a negative Poisson ratio, thus used in mechanical and optical metamaterials applications in shielding structures, invisible cloaking, and high-gain antennas. However, until now, experimental efforts in making patchy NPs and directing their assembly into open structures have been limited due to three challenges: First, the synthetic challenge of making highly uniform patchy NPs, due to the difficulty in precisely controlling the patch size, shape, and patterns at the nanoscale; Second, a design challenge to encode directional multicomponent interactions due to their nonadditivity; and third an imaging challenge to observe and control the assembly kinetics of NPs in the liquid media at the single-particle level. All three challenges have been being addressed by three breakthroughs made during my Ph.D. study as detailed below. Precise patterning of polymer patches on NPs: As a first demonstration, gold nanoprisms having patches only on their highly-curved tips were achieved. Built upon this effort, on one hand, I utilized the handle of polymer–polymer attraction to induce single- and double-patched prisms at high yields (> 80%) via supramolecular “bandwagoning” effect. Our theory and simulation unveil the thermodynamic origin of asymmetric grafting and accurately predict experimental observations at all levels—from particle-level patterning to nanoscopic size and shape of patches. On the other hand, I developed a new mechanism of “atomic stencil” where ionic additives selectively mask certain facets of NPs to pattern polymer patches. The approaches are generalizable to various shapes and compositions of NPs aiding many different applications by site-specific chemistries and interactions (e.g. catalysis, delivery, and directed assembly). Controllable assembly of patchy NPs: I demonstrated two distinct strategies to assemble patchy NPs – by either their patches or non-patched surfaces. First, tip-patched prisms can assemble via interactions of their exposed gold surfaces into twisted, chiral structures (stars and slanting diamonds). Second, interpolymer complexation of patches connects prisms by their tips into “nano-bowties” and reconfigurable open networks. These strategies can be applied to a whole library of patchy NPs to assemble open structures with long-anticipated features (e.g., > 70% porosity, low thermal conductivity, and tailored photonic bandgaps). Direct visualization and in situ control of superstructures: a movie-taking platform of liquid-phase transmission electron microscopy (TEM) has been developed to acquire unprecedented knowledge of the assembly pathways at the single-particle level. Using gold nanospheres as a model system, I investigated the assembly pathways of NPs into defect-free face-centered cubic superlattices. The spatiotemporal expansion of supracrystalline domains is mapped via particle tracking, revealing remarkable atomic mimicry of layer-by-layer growth and memory effects. Furthermore, by flowing aqueous electrolytes in situ, we investigate the reconfiguration dynamics of open networks assembled from tip-patched nanoprisms, potentially aiding adaptable plasmonics and optics. Lastly, we demonstrated that highly polydisperse plates can form long-range hexagonal order due to a hierarchical assembly pathway, observed in optical microscopy. In summary, my thesis integrates polymer physics, nanocolloids, and liquid-phase TEM for the first time to connect nanoscale molecular chemistry all the way to micron-scale assembly kinetics. The novel synthetic strategies enable a priori design of morphologies and symmetry with nanoscale-precision towards functional polymer patterns for plasmonics, catalysis, sensors, actuators, and data storage devices. Furthermore, the direct manipulation of NPs assembly structures and pathways under liquid-phase TEM provides ways to achieve reconfigurable optoelectronic and mechanical properties for future applications in invisible cloaking coatings, high-gain antennas, and shielding structures.

Graduation Semester

2022-08

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Ahyoung Kim

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