(6gk) Complex Nano-Architectures from Self-Assembly and Surface-Confined Chemistry for Energy Storage and Beyond

Self-assembly of amphiphilic molecules such as surfactants and block copolymers has enabled the fabrication of ordered morphologies with single to 10s of nanometers dimensions, including ordered three-dimensionally (3D) co-continuous network structures. The utilization of such self-assembling molecules to structure-direct inorganic, organic, and polymeric materials allowed the fabrication of nano- and mesoporous functional materials with structure-based performance enhancements in numerous applications, including energy storage and conversion. While the range of nanostructured materials between the sub-nanometer to mesoscale (<50 nm) is well explored, there exists a gap in characteristic length scales of structured and porous materials in the range of 100s of nanometers. This range is of particular interest to obtain well-defined architectures and assemblies of multiple functional materials layered on top and confined within each other for exploring solid interfacial phenomena and to obtain radically new device concepts and designs, such as folding all device components into a single hybrid architecture. In my research program, I aim to develop methods to obtain 3D structured functional materials and multicomponent architectures with pore sizes and characteristic dimensions beyond the mesoscale in the 100s of nanometers. To achieve such hybrid architectures and devices, my efforts will initially focus on three distinct directions:

(1) Self-assembled 3D structures beyond the mesoscale (100-1000 nm) through solution assembly, ultra-large self-assembling amphiphiles, and controlled phase-separation. In particular, initial focus will be put on the use of block copolymers as the interfacially active, amphiphilic molecule in microemulsions, lyotropic liquid crystals, bicontinuous interfacially jammed emulsion gels, and for the combination of macro- and microphase separation. Furthermore, I aim to develop and synthesize a new class of ultra-large soft amphiphiles such as colloid-like molecular Janus architectures. Since the parameter space of self-assembly and structuring methods is very large, we will employ droplet-based microfluidics to screen for optimal conditions and compositions using small amounts of materials at fast rates.

(2) Multilayered three-dimensionally inderdigitated nanostructures from surface confined syntheses methods on nanopore surfaces for rationally designed nano-integrated architectures. There exists a lack of syntheses and deposition techniques that can conformally coat nanoporous but macroscopic materials with high uniformity. In addition to gas-phase deposition processes, I aim to develop electrodeposition methods of inorganics and polymers, as well as layer-by-layer syntheses using surface sol-gel (SSG) and surface-initiated step-growth polymerizations, respectively, on high-surface area nanostructures. These efforts will be complimented with microfluidic reactors for fast screening of synthesis conditions.

(3) Three-dimensionally integrated battery architectures (“3D Batteries”). Our initial focus for applying multilayered 3D nanoarchitectures is the development of so-called 3D batteries, in which the anode and cathode are interpenetrating each other in three dimensions on the nano- or microscale. The integrated electrodes are fully separated by a 3D continuous solid electrolyte layer to prevent electrical contact between the electrodes while keeping electrode distances to a minimum for fast ion transport. The small distance between the electrodes conceptually allows very fast charging and discharging of the batteries, while the lack of porosity due to the integrated architecture is volumetrically efficient and enables high energy densities.

Another focus of my research program will be the development of novel dynamically responsive materials. We will utilize thiol-ene chemistry-derived polymer networks as ultra-durable hosts to attach dynamically responsive molecular moieties. These dynamic networks will also be synthesized in 3D nanotemplates to study the effect of nanostructuring in combination with molecular functionality and architecture on the dynamic bulk behavior and responsive properties. One particular class of material we will study are liquid crystal elastomers (LCEs), including the development of new LCE monomers from inexpensive precursors in simple syntheses and the alignment of LCE orientation in nanostructures and on liquid surfaces and interfaces.

Research Experience:

My research program will build on my experience in block copolymer structure direction of functional inorganic materials for energy applications that I obtained during my PhD under the supervision of Prof. Uli Wiesner at Cornell University, and expertise in emulsion templating of dynamically responsive polymeric materials from droplet microfluidics that I obtained during my current postdoctoral research position with Prof. David Weitz at Harvard University.

During my PhD, we developed and fabricated a trifunctional three-dimensionally integrated nanohybrid, a so-called 3D battery, featuring an ordered 3D networked (gyroidal) mesoporous carbon anode, coated with an ultra-thin polymer electrolyte, and backfilled with an inorganic-polymer cathode composite. We employed a combination of molecular self-assembly, electropolymerization, and nano-confined synthesis to obtain a final monolithic solid-state 3D architecture with each layer possessing a thickness below 20 nm. The synthesized 3D nanohybrid with macroscopic overall dimensions exhibited battery-like properties [1]. This first demonstration of a functional 3D battery with nanoscale dimensions and interdigitation was based on and only possible due to our development of highly stable gyroidal mesoporous carbon monoliths with an ultra-large pore size of 40 nm and high temperature stability up to 1600 ºC [2]. We employed these ordered mesoporous carbons to demonstrate their most influential structural and chemical properties on the electrochemical performance as sulfur hosts in lithium-sulfur batteries [3]. We further showed the limitations of atomic layer deposition (ALD) on coating nanoporous monolithic materials with macroscopic dimensions, with a maximum deposition depth of 10 microns into 40 nm 3D pores [4]. Furthermore, we synthesized hierarchically macro- and mesoporous inorganic structures with graded macroporosity using polymer phase separation on multiple length scales [5,6].

In my postdoctoral research in the soft condensed matter lab of Prof. David Weitz, I pioneered the synthesis of dynamically responsive microcapsules employing complex drops from microfluidic fabrication. In particular, I developed functional monomer systems with a controlled hydrophobic-to-hydrophilic transition for microfluidic emulsion processing. The highly uniform and tunable microcapsules reversibly change their size, shape, and permeability in response to stimuli such as pH, ionic environment, and light for controlled capture, trap, and release of cargo [7].

Teaching Interests:

During my education and research career I have been part of a variety departments giving me a diverse background in chemistry, materials science and engineering, and applied physics. I am interested and prepared to teach organic, solid state, polymer, physical and general chemistry, electrochemistry and thermodynamics on the introductory level, and polymer chemistry, polymer physics, materials chemistry, and materials characterization at an advanced undergraduate and graduate level. Furthermore, I am very interested in teaching interdisciplinary courses of interest to a wide variety of students such as nanomaterials, nanocharacterization, surface deposition and characterization techniques, electrochemical devices and materials, and materials phase behavior at any level.

During my undergraduate education in Germany, I learned to appreciate the importance of taking the classroom material into the lab to put it to practical use. In particular, the application of physical and chemical principles in experimental setups and projects that allow the students to explore and discover the utility and applicability of these concepts, but also to realize shortfalls and limits of certain models, are crucial to understand when and how to use them. Hence, I would teach most courses in combination with small projects where the students can apply analytical methods using a combination of characterization tools materials of interest to the students. This will give students an appreciation of the physical concepts, as well as the importance of exhaustive characterization with complementary techniques. In particular in polymer science, most courses are focused on the synthesis and the fundamental physics of polymers. I will develop a course that introduces the breadth of polymer characterization tools such as size exclusion chromatography, light scattering, rheology, X-ray scattering, osmolarity, and electron microscopy in a combined picture, and introduce them to students as complementary characterization tools in practical use.

Selected Publications:

[1] J. G. Werner, G. G. Rodríguez-Calero, H. D. Abruña, U. Wiesner, “Block copolymer derived 3-D interpenetrating multifunctional gyroidal nanohybrids for electrical energy storage” Energy Environ. Sci. 11, 1261-1270 (2018).

[2] J. G. Werner, T. N. Hoheisel, U. Wiesner, “Synthesis and Characterization of Gyroidal Mesoporous Carbons and Carbon Monoliths with Tunable Ultralarge Pore Size”, ACS Nano 8 (1), 731-743 (2014).

[3] J. G. Werner, S. S. Johnson, V. Vijay, U. Wiesner, “Carbon-Sulfur Composites from Cylindrical and Gyroidal Mesoporous Carbons with Tunable Properties in Lithium-Sulfur Batteries”, Chem. Mater. 27, 3349-3357 (2015).

[4] J. G. Werner, M. Scherer, U. Steiner, U. Wiesner, “Gyroidal Mesoporous Multifunctional Nanocomposites via Atomic Layer Deposition”, Nanoscale 6, 8736-8742 (2014).

[5] S. A. Hesse,* J. G. Werner,* U. Wiesner, “One-pot Synthesis of Hierarchically Macro and Mesoporous Carbon Materials with Graded Porosity”, Macroletters 4, 477-482 (2015). (*Contributed equally)

[6] Y. Gu, J. G. Werner, R. M. Dorin, S. W. Robbins, U. Wiesner, “Graded Porous Inorganic Materials Derived from Self-Assembled Block Copolymer Templates”, Nanoscale 7, 5826-5834 (2015).

[7] J. G. Werner, David A. Weitz et al., “Dynamic Microcapsules with Rapid and Reversible Permeability Switching “ Adv. Funct. Mater. 2018, in review; „Hydrogel Microcapsules with Dynamic pH-responsive Properties from Methacrylic Anhydride” Macromolecules 2018, in review.