(7jn) Towards Stronger and Smarter Materials via the Hybridization and Engineering of Dimensionality and Topology

Macroscopic preparation of materials with precise structure control at the atomic and molecular level is an ultimate goal of chemical engineering, and this could lead to the production of materials with versatile properties and tangible technological applications. Despite our ability to synthesize molecules and nanoparticles, atomic control by introducing or compositing single atom defects or discontinuities in materials at a large scale remains a dream. However, the emergence of large-area, two-dimensional (2D) materials which have the thickness of a single atom or unit cell, such as graphene, molybdenum disulfide, or hexagonal boron nitride (hBN), may help to realize this dream. My research interests lie in the fundamental task of synthesizing 2D materials, polymers, nanoparticles, and their molecular composites and nanocomposites with precise structural control and the process of scaling up. The basic idea is to use material hybridization, dimension transformation, and topology optimization to achieve stronger and smarter materials. Hybridizing layers of 2D materials or intercalating/interfacing 2D layers with composite matrix materials such as polymers, is a simple, yet efficient, way to achieve atomic control, and can scale up to the macroscopic level. Simultaneously, these 2D materials are intriguing nanoinclusions that can be engineered to impart exotic mechanical reinforcements and various other functions as matrix composites. A further dimension transformation from 2D to 3D (i.e., by creating a 3D composite body comprised exclusively of 2D layers) can induce new and exotic functions that depend on the topology of the 3D object.

Postdoctoral Projects:

- Under supervision of Michael S. Strano, Chemical Engineering Department of MIT:

“Design And Synthesis Of Carbon-based Chainmaille Structures for Flexible, Ultra-lightweight Protection”, funded by U.S. Army Research Office (ARO);

A Conceptual Model of Ambient Armor and Issues Relating to Experimental Realization, funded by ARO;

“FATE: Foldable and adaptive Two-Dimensional Electronics”, Thrust II – Folding, MURI project, funded by Air Force Office of Scientific Research;

Thermal Management Technologies for Low Temperature Undersea Dive Persistence: a Novel Arctic Diving Suit, funded by U.S Navy.

Ph.D. Dissertation:

“Study on Tailoring Chain Topologies of Ethylene Copolymers and Their Functionalization”
- Under supervision of Wen-Jun Wang (College of Chemical and Biological Engineering, Zhejiang University, China), Shiping Zhu (Department of Chemical Engineering, McMaster University, Canada), and Zhibin Ye (Bharti School of Engineering of Laurentian University, Canada)

Fellowships:

2013 Fellowship for Outstanding Doctoral Dissertation of Zhejiang University, China;
2011 Fellowship for Excellent Doctoral Student granted by Ministry of Education, China;

Research Experience:

As a scientist trained with chemical engineering fundamentals, my research interfaces polymer science, nanotechnology, material mechanics, catalysis, and sensors. Specifically, I have focused on the precise synthesis and characterization of polymers, 2D materials, nanoparticles and their nanocomposites, and the experimental and theoretical study of their mechanical, electrical, optical, catalytic properties and sensing behaviors:

As a postdoc, I have worked on: (1) Layered and scrolled polymer nanocomposites with aligned semi-infinite 2D inclusions, which show substantial mechanical reinforcement and interesting electrical and optical properties at highly reduced volume fraction of 2D inclusions such as graphene. (2) Autoperforation of 2D materials for generating two terminal memresistive Janus particles. This autoperforation technique can guide Griffith facture of 2D materials, which provides a means of spontaneous assembly for surfaces comprised of 2D molecular surfaces. With this technology, I have created colloidal microparticles that can function as particulate electronic devices capable of collecting and storing digital information in their environment. (3) Ambient armor (AA) concept for stand-off projectile defense and its mathematical modeling. I have explored the theoretical possibility of new materials, particularly lightweight 2D nanocomposites with high toughness and elongation, for projectile protection in a stand-off way. (4) Collaborative work with other lab members. I have also involved in a diverse of projects including polymer-wrapped single-walled carbon nanotube sensors for carbohydrates detection, nitroaromatic detection with plant nanobionics, chemical doping of carbon nanotube fibers for electrical energy generation, 2D heterostructures and their photoresponse, strain engineering of 2D materials, thermal diodes, self-healing and growing hydrogels, synthetic state machine particles, and others.

As a PhD student, I mastered the synthesis of late transition metal catalysts, the catalytic polymerization of olefins, and “living”/controlled radical polymerization of functional monomers. Combining different polymerization techniques, I achieved a synergistic control of the chain sequences, topologies, and functionalities of ethylene polymers. I synthesized and characterized a library of functional polyethylenes (PEs) hybrids with various topologies including tree-like, hyperbranched star, miktoarm star and cross-linked mesh, and well-designed functionalities like tertiary amines, ethylene glycols, and amino acid groups. The characteristic chain architectures and functionalities endow the polymers with fascinating solution and melt properties and gas-sensitive behavior in aqueous solution, and I intensively characterized these properties with triple-detection gel permeation chromatography, rheometer, thermal analysis, and other techniques. I further demonstrated the new applications of these functional PEs as efficient supports for metal nanoparticles and organocatalysts to achieve a highly active and selective catalysis with good recyclability.

Teaching Interests:

Personally, I believe that one of the greatest pleasures of being a professor is teaching and mentoring students. During my Ph.D. and postdoc, I have mentored more than 17 students from different nations and cultural backgrounds with fruitful achievements, including 6 undergraduates, which have received awards and honors such as the “Excellent Graduation Thesis of Zhejiang University”, and the “National University Student Innovation Program” of China. In addition, one student’s work was highlighted by the newsletter of Material Processing Center of MIT. I have had valuable experience in teaching various courses in the fields of polymer science and reaction engineering, and I have been invited as a lecture in the Nano-Engineered Composite Aerospace Structures Consortium of MIT. With an interdisciplinary background, I can teach different curriculums in the field of polymer science, nanotechnology, nanocomposites, and catalysis and would like to develop new interdisciplinary courses and international teaching programs in the future.

Future Directions:

In future, I want to build an interdisciplinary research group in the fields of (I) lightweight and high-strength materials for protective and space applications and (II) active and intelligent materials for catalytic and sensing applications. In particular, I plan to work on: (1) The precise synthesis of large-area, high quality 2D materials and their molecular composites and nanocomposites via wet-chemistry methods. (2) The fundamental study of the reinforcing mechanism of these composites in aspects of mechanical, optical, electrical, and catalytic properties. (3) The topology design and optimization of the 3D composite body and the development of new methods and processes to realize the dimension transformation from 2D to 3D. An ultimate goal is to achieve a scalable production of 3D composite bodies with outstanding mechanical performance, chemical stability, and an integration of multiple functions such as energy generation and storage, sensing, memorizing, communicating, actuating, catalysis, and others. This composite can be a microparticle that can perform as a smart and autonomous device for biomedical and Internet of Things applications.

Selected Publications:

- 19 peer-reviewed journal articles (11 first-authored papers), 3 patents, 1 book chapter.

(1) Liu, P.; Jin, Z.; Katsukis, G.; Drahushuk, L. W.; Shimizu, S.; Shih, C.-J.; Wetzel, E. D.; Taggart-Scarff, J. K.; Qing, B.; Van Vliet, K. J., Layered and scrolled nanocomposites with aligned semi-infinite graphene inclusions at the platelet limit. Science 2016, 353, 364.

(2) Liu, P.; Liu, A. T.; Kozawa, D.; Dong, J.; Saccone, M.; Koman, V. B.; Wang, S.; Son, Y.; Wong, M. H.; Strano, M. S. Autoperforation of 2D Materials for Generating Two Terminal Memresistive Janus Particles. Submitted to Nat. Mater., out for review.

(3) Liu, P.; Cottrill, A. L.; Kozawa, D.; Koman, V. B.; Kaplan, Liu, A. T.; Tran, T.; Wong, M. H.; Strano, M. S. Emerging trends in 2D nanotechnology that are redefining our understanding of Nanocomposites. Nano Today, invited review, prepared.

(4) Liu, P.; Strano, M. S., Toward Ambient Armor: Can New Materials Change Longstanding Concepts of Projectile Protection? Adv. Funct. Mater. 2016, 26, 943.

(5) Wong, M. H.; Giraldo, J. P.; Kwak, S.-Y.; Koman, V. B.; Sinclair, R.; Lew, T. T. S.; Bisker, G.; Liu, P.; Strano, M. S., Nitroaromatic detection and infrared communication from wild-type plants using plant nanobionics. Nat. Mater. 2016, 16, 264.

(6) Liu, A. T.; Kunai, Y.; Liu, P.; Kaplan, A.; Cottrill, A. L.; Smith-Dell, J. S.; Strano, M. S. Electrical Energy Gene-ration via Reversible Chemical Doping on Carbon Nanotube Fibers. Adv. Mater. 2016, 28, 9752.

(7) Son, Y.; Li, M.-Y.; Cheng, C.-C.; Wei, K.-H.; Liu, P.; Wang, Q. H.; Li, L.-J.; Strano, M. S., Observation of switchable photoresponse of a monolayer WSe2–MoS2 lateral heterostructure via photocurrent spectral atomic force microscopic imaging. Nano Lett. 2016, 16, 3571.

(8) Wang, S.; Liu, P.; Wang, W.-J.; Zhang, Z.; Li, B.-G., Hyperbranched polyethylene-supported L-proline: a highly selective and recyclable organocatalyst for asymmetric aldol reactions. Catal. Sci. Technol. 2015, 5, 3798.

(9) Liu, P.; Lu, W.; Wang, W.-J.; Li, B.-G.; Zhu, S., Highly CO₂/N₂-switchable zwitterionic surfactant for Pickering emulsions at ambient temperature. Langmuir 2014, 30, 10248.

(10) Liu, P.; Dong, Z.; Ye, Z.; Wang, W.-J.; Li, B.-G., A conveniently synthesized polyethylene gel encapsulating palladium nanoparticles as a reusable high-performance catalyst for Heck and Suzuki coupling reactions. J. Mater. Chem. A 2013, 1, 15469.

(11) Liu, P.; Ye, Z.; Wang, W.-J.; Li, B.-G., Hyperbranched Polyethylenes Encapsulating Self-Supported Palladium (II) Species as Efficient and Recyclable Catalysts for Heck Reaction. Macromolecules 2012, 46, 72.

(12) Liu, P.; Lu, W.; Wang, W.-J.; Li, B.-G.; Ye, Z.; Zhu, S., Synthesis and Characterization of PE-b-POEGMA Copolymers Prepared by Linear/Hyperbranched Telechelic Polyethylene-Initiated ATRP of Oligo(ethylene glycol) Methacrylates. In Progress in controlled radical polymerization: mechanisms and techniques, American Chemical Society: 2012; Vol. 4, 39.

(13) Liu, P.; Landry, E.; Ye, Z.; Joly, H.; Wang, W.-J.; Li, B.-G., “Arm-first” synthesis of core-cross-linked multiarm star polyethylenes by coupling palladium-catalyzed ethylene “living” polymerization with atom-transfer radical polymerization. Macromolecules 2011, 44, 4125.