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Synthesis and Self-Assembly of Bottlebrush Block Polymers: Molecular Architecture and Materials Design

Citation

Chang, Alice B. (2018) Synthesis and Self-Assembly of Bottlebrush Block Polymers: Molecular Architecture and Materials Design. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/4xdv-9302. http://resolver.caltech.edu/CaltechTHESIS:05302018-104109274

Abstract

Bottlebrush polymers represent a unique molecular architecture and a modular platform for materials design. However, the properties and self-assembly of bottlebrush polymers remain relatively unexplored, in large part due to the synthetic challenges imposed by the sterically demanding architecture. This thesis describes our work to close this gap, connecting (1) the synthesis of polymers with precisely tailored molecular architectures, (2) the study of fundamental structure-property relationships, and (3) the design of functional materials.

Chapter 1 introduces key concepts related to polymer architecture and block polymer phase behavior. Recent developments in the synthesis and self-assembly of bottlebrush block polymers are highlighted in order to frame the work presented in Chapters 2–6.

Chapter 2 introduces a versatile strategy to design polymer architectures with arbitrary side chain chemistry and connectivity. Simultaneous control over the molecular weight, grafting density, and graft distribution can be achieved via living ring-opening metathesis polymerization (ROMP). Copolymerizing a macromonomer and a small-molecule co-monomer provides access to well-defined polymers spanning the linear, comb, and bottlebrush regimes. This design strategy creates new opportunities for molecular and materials design.

Chapter 3 explores the physical consequences of varying the grafting density and graft distribution in two contexts: block polymer self-assembly and linear rheological properties. The molecular architecture strongly influences packing demands and therefore the conformations of the backbone and side chains. Collectively, these studies represent progress toward a universal model connecting the chemistry and conformations of graft polymers.

Chapter 4 discusses the phase behavior of ABA' and ABC bottlebrush triblock terpolymers. Low-χ interactions between the end blocks promote organization into a unique mixed-domain lamellar morphology, LAMP. X-ray scattering experiments reveal an unusual trend: the domain spacing strongly decreases with increasing total molecular weight. Insights into this behavior provide new opportunities for block polymer design with potential consequences spanning all self-assembling soft materials.

Chapter 5 describes other physical consequences of low-χ block polymer design. The ternary phase diagrams for ABC, ACB, and BAC bottlebrush triblock terpolymers reveal the influences of low-χ A/C interactions, frustration, and the molecular architecture. Potential non-equilibrium effects and crystallization in these bottlebrush polymers will also be discussed.

Chapter 6 describes applications of bottlebrush polymers as functional materials. Self-assembly enables mesoscale structural control over many materials properties, such as reflectivity, conductivity, and modulus. The synthetic methods (Chapter 2) and physical insights (Chapters 3−5) provided in previous chapters illustrate opportunities for materials design. We will discuss AB brush diblock polymers that self-assemble to photonic crystals and ABA brush triblock copolymers in solid polymer electrolytes.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Polymer chemistry; polymer physics; bottlebrush; block copolymer; block polymer; self-assembly; olefin metathesis
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Awards:Herbert Newby McCoy Award, 2018.
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Grubbs, Robert H.
Thesis Committee:
  • Tirrell, David A. (chair)
  • Grubbs, Robert H.
  • Dougherty, Dennis A.
  • Wang, Zhen-Gang
Defense Date:25 May 2018
Non-Caltech Author Email:abchang0 (AT) gmail.com
Funders:
Funding AgencyGrant Number
National Defense Science and Engineering Graduate FellowshipUNSPECIFIED
National Science Foundation (NSF)CHE-1212767
National Science Foundation (NSF) CHE-1502616
Department of Energy (DOE)DE-AR0000683
Record Number:CaltechTHESIS:05302018-104109274
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:05302018-104109274
DOI:10.7907/4xdv-9302
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/jacs.7b00791DOIArticle adapted for Chapter 2.
http://dx.doi.org/10.1021/jacs.7b10525DOIArticle adapted for Chapter 2.
http://dx.doi.org/10.1021/acsnano.7b06664DOIArticle adapted for Chapter 3.
http://dx.doi.org/10.1021/acsmacrolett.8b00116DOIArticle adapted for Chapter 3.
http://dx.doi.org/10.13020/D6T97MDOIPrimary data for the previous article.
http://dx.doi.org/10.1073/pnas.1701386114DOIArticle adapted for Chapter 4.
http://dx.doi.org/10.1021/ja5093562DOIArticle adapted for Chapter 6.
http://dx.doi.org/10.1021/acs.macromol.5b00880DOIArticle adapted for Chapter 6.
http://dx.doi.org/10.1002/polb.23927DOIArticle adapted for Chapter 6.
http://dx.doi.org/10.1021/jacs.6b08795DOIArticle adapted for Chapter 6.
ORCID:
AuthorORCID
Chang, Alice B.0000-0001-5036-2681
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:10972
Collection:CaltechTHESIS
Deposited By: Alice Chang
Deposited On:12 Jun 2018 19:54
Last Modified:12 Dec 2018 18:17

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PDF (Chapter 1 - Introduction) - Final Version
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PDF (Chapter 2 - Control over Graft Polymer Architecture via ROMP) - Final Version
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PDF (Chapter 6 - Applications of Bottlebrush Polymers in Functional Materials) - Final Version
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