(6gw) Materials Chemistry As Engineering Solutions: Metamaterials, Energy and Water

Future Research

My research is at the intersection of chemical engineering, chemistry and materials science, relying concepts from nanotechnology, plasmonics, mechanics and mathematics. I aspire to uncover multifarious technological holy grails by fully comprehending their underlying mechanisms and dynamics. My independent research will answer to the question of “how materials chemistry can be engineering solutions for optoelectronics, energy and environmental problems”.

Recently, chiroptical meta-materials have gained tremendous attention due to a wide range of advantageous applications from anomalous control of light to sensing of biomolecules. These have mostly been touched by top-down approaches (e.g. lithography), while bottom-up approach has been mostly left as untapped. Hence, to open new doors, I will synthesize optically active inorganic materials, and then assembled them with organic ligands/polymeric backbone for high-performing materials. Eventually, these materials will be used in fabrications of devices.

Efficient, clean energy production and environmental pollutions are constant critical issues of the sustainable future of humanity. I plan to leverage modern synthetic strategies to produce precisely controlled polymeric molecular structures which will be used for selective and efficient transport of various ions/phonons for fuel cells, thermal conduction, and air & water filtration applications. The expertise obtained during these studies can also be applied to water desalination and redox flow batteries.

Post-Doctoral Research

• "Designed Polymers for Energy (Fuel Cell Membranes) and Environment (Hg(II) Removal) Applications"
• Advisor: Prof. Timothy M. Swager, Massachusetts Institute of Technology, Chemistry

Postdoctoral research trained me to become a materials chemist. Through multiple projects, I have demonstrated how rationally designed polymeric systems can contribute remarkably to the development of new engineering tools that tackle environmental problems of our society, especially on energy and water.

First, I demonstrated how free volume promoting moieties and charge delocalized polymer backbone can help enhance the conductivity and stability of anion exchange membranes for fuel cell applications. The addition of unfunctionalized triptycene (free-volume promoting) copolymer into imidazolium poly (ether sulfone) had improved the membrane’s conductivity, minimized dimensional changes, and enhanced stability. These enhancements are the result of nanophase separation and internal free volume. Extremely stable pyrozolium type cations are also used as ion conducting moieties.

Another project showed how the use of redox active polyaniline can achieve the electrochemically controlled reversible capture and release of highly toxic Hg(II) in water. Polyaniline naturally adsorbs Hg(II), and a subsequent dose of oxidation potential induces the release. Nanofiber geometry of polyaniline offered faster adsorption kinetics. Additional sulfur chelating groups boosted its uptake capacity.

Graduate Research

• "Self-Organized Nanoparticles for Stretchable Conductors and Chiroptical Materials"
• Advisor: Prof. Nicholas A. Kotov, University of Michigan, Chemical Engineering

My graduate work, “Science and Engineering on Nanocomposites”, trained me to become a chemical engineer with interdisciplinary expertise in nanotechnology, materials science, electronics, mechanics and photonics. The projects demonstrated how external stress can re-organized nanoparticles in the composites, for discovering fundamental understandings of mechanisms and dynamics for unique electronic and optical properties.

An excellent stretchable conductors were demonstrated from self-organized gold nanoparticles using a highly stretchable polyurethane matrix. Macroscale free-standing samples were prepared using a layer-by-layer assembly of positively-charged polyurethanes and negatively-charged gold nanoparticles. The dynamic self-organization of polymer-nanoparticle assemblies produced composites with high conductivity and stretchability.

Self-organization of the assemblies also demonstrated chiroptical nanocomposites for applications of photonic metamaterials. The conformal layer-by-layer deposition on pre-twisted substrates offers a distinctive advantage when producing macroscale photonic materials. Chiroptical activity had increased up to ten fold upon stretching samples and was reversibly tunable. S-like chiroptical 3D patterns responsible for optical properties appeared as a consequence of buckling surface instabilities.

Selected Publications

1. Kim, T.M. Swager, “Charge Delocalized Anion Exchange Membranes: Extreme Stability and High Conductivity” (Manuscript in Preparation)
2. Kim, Z. Lin, I. Jeon, T.V. Voorhis, T.M. Swager, “Polyaniline Nanofiber Electrodes for Capture and Release of Mercury(II)” (To be submitted)
3. Kim†, L. Moh†, T.M. Swager, “Anion Exchange Membranes: Enhancement by Addition of Unfunctionalized Triptycene Poly(Ether Sulfone)s” ACS Applied Materials & Interfaces, 2017, 9, 42409–42414.
4. Kim†, B. Yeom†, O. Arteaga, S.J. Yoo, S.G. Lee, J.G. Kim, N.A. Kotov, “Reconfigurable Chiroptical Nanocomposites with Chirality Transfer from the Macro- to the Nanoscale” Nature Materials, 2016, 15, 461-468.
5. Kim, J. Zhu, B. Yeom, M.D. Prima, X. Su, J.G. Kim, S.J. Yoo, C. Uher, N.A. Kotov, “Stretchable Nanoparticle Conductors with Self-Organized Conductive Pathways” Nature, 2013, 500, 59-63.
6. Kim, K. Koh, M.F. Roll, R.M. Laine, A.J. Matzger, “Porous Networks Assembled with Octa Phenyl Silsesquioxanes as Building Blocks”, Macromolecules, 2010, 43, 6995-7000.

† indicates equal contribution

Teaching Interests:

Teaching and Mentoring Experience

At the University of Michigan, I served as a graduate student instructor for CHE460 Chemical Engineering Laboratory II, a core senior lab class, which requires comprehensive chemical engineering knowledge for undergraduate students (student evaluation: 4.7 / 5.0). My course preferences are thermodynamics, chemical reaction engineering, transport processes, material/energy balances, organic chemistry, physical chemistry, polymer chemistry, and graduate classes for nanoscience and engineering. However, I am capable of teaching other graduate and undergraduate core courses as well. I also look forward to the opportunity to mentor students. During my PhD studies, I had mentored eight students (1 PhD, 2 masters, 4 undergraduates and 1 high school) for off-shoot projects of the electronic and optical nanocomposites. Their mentorship has allowed me to not only gain new technical skills, but also appreciate the positive effect that mentorship can have on a student's professional development.

Teaching Philosophy

My teaching philosophy is underpinned by competence, autonomy, connectedness and diversity. My goal as a teacher, as a mentor, is to inspire innovation, enhance performance and make lab life more enjoyable.

Competence is a prerequisite. I discovered that the best performance is often achieved at an intermediate difficulty task level. For example, for first year graduate students, a good starting project is the synthesis and characterization of nanoparticles. If the student succeeds, then we can move on to more advanced level tasks involving the optimization and assembly for device fabrications.

Autonomy is essential for motivation. Autonomy is the sense that the project emanates from the person and not from an external source. Using punishment or negative feedback will only stifle their enthusiasm. The optimal degree of autonomy is specific to each individual and changes over time. Thus, the advisor and his student need to determine and adjust this together.

Social connectedness. The need for connectedness encompasses the striving to care for others, to feel that others relate to you in mutually supportive ways, and to feel a satisfying involvement with the entire lab. Having an effective communication within the lab is a key to social connectedness. For example, in the Swager lab, we have a mentoring system to pair graduate students and postdocs. Also, we regularly have a dinner together and frequently play tennis or basketball together to build team bonding. These are good examples for lab members to be kept connected.

I am committed to promoting and supporting diversity in my classroom and in my lab. This includes diversity of experience, way of thinking, and ideas in addition to demographic diversity. During my PhD and postdoc programs, I have participated in many outreach activities such as serving as a mentor at alternative high school, volunteers for science day etc. I firmly believe that unparalleled performances can only be achieved with the collaborative efforts from a diverse group of people.

For more information, please visit my website: http://yoonseobkim.com/.