(2ht) Molecularly Programmed Dynamic Polymers for Responsive Materials

Research Interests: Today’s commercial polymeric materials are commonly homopolymers, random copolymers, simple block copolymers, or polymer blends with non-specific interactions, where functional properties are predominantly dictated by molecular weight. This stands in contrast to natural biopolymers such as proteins whose function is not determined by their length but instead by the sequence of their monomers (i.e., amino acids). Moreover, nature uses different biopolymers in tandem, whose interactions are sequence-encoded. These discrepancies represent an exciting opportunity – the design, characterization, and combination of synthetic polymers with molecularly-programmed interactions into new functional materials. Dynamic polymers, which incorporate dynamic bonds (e.g., hydrogen-bonding, π-π stacking, metal-ligand coordination) into traditional synthetic backbones, are an ideal platform to achieve molecularly specific interactions. I am interested in studying these dynamic polymers to develop sequence-focused structure-property relationships and design responsive materials that adapt their internal structure and material properties with molecular-level precision. The resulting materials have applications including skin-like electronics, self-healing coatings and adhesives, selective membranes, solid-state battery electrolytes, and recyclable plastics.

Research Background:

As a faculty member, I will build upon the synthetic and characterization tools I developed in my doctoral research at Stanford University working with Prof. Zhenan Bao. This work focuses on periodic dynamic polymers, in which controlled periodicity along the chain backbone leads to ordered microstructures and enhanced material properties. The key accomplishments of this work include:

(i) We have shown that periodic placement of directional dynamic bonds along the chain backbone allows for spontaneous self-assembly into bundled supramolecular nanofibers. Moreover, through the synthesis and characterization of a range of molecular architectures, we identified key molecular design rules governing self-assembly in the melt state.

(ii) By using the above principles, we designed a new dynamic polymer that only assembles under strain. These strain-induced supramolecular structures temporarily stabilize the highly stretched chains, and their destabilization upon heating enables robust and high energy density shape memory behavior as the polymers return to their isotropic, disordered melt state. This polymer has the highest energy density for one-way shape memory reported to date.

In addition to my doctoral studies, my research background includes independent research conducted at the University of Cambridge with Prof. Jacqueline Cole on data-driven discovery of dye-sensitized solar cells and at North Carolina State University with Prof. Michael Dickey on liquid metal soft electronics.

Teaching Interests:

I strongly believe that the outcome of successful research is not only the creation of impactful knowledge, but also the conscientious training of independent scientific thinkers. This belief extends into the classroom, where exceptional instructors communicate important scientific concepts while also training students to think critically. This requires the intentional creation of an inclusive learning environment accessible to students of all backgrounds (where, above all, students feel comfortable expressing uncertainty and asking questions). I am committed to fostering this environment as well as attentively and fully supporting all students with whom I interact as a faculty member.

At Stanford, I have served as a teaching assistant for two quarters for the undergraduate senior design research capstone course. I received the Outstanding Chemical Engineering Teaching Assistant Award from the department both years (2020 and 2021) as well as the Centennial Teaching Assistant Award (2021) from the university. Outside of serving as a teaching assistant, I have sought out ways to mentor others and give back to communities around me including: serving as a mentor to first-time department teaching assistants, participating in DEI chats with prospective students, speaking multiple years as a summer REU volunteer for undergraduate chemical engineering, mentoring first-generation or low-income (FLI) and underrepresented minority (URM) incoming graduate students as a Stanford Summer First mentor, and guest lecturing for ENGR 50E (Introduction to Materials Science).

My background in chemical engineering has prepared me to teach any core course in the undergraduate or graduate curriculum.

Selected National Honors & Awards:

• National Defense Science and Engineering Graduate Fellow (2020-2023)
• National Science Foundation Graduate Research Fellowship (2017-2020)
• Churchill Scholarship (2017-2018)
• Barry Goldwater Scholarship (2016)
• Park Scholarship (2013-2017)

Selected Publications (5 of 12):

C.B. Cooper^†, S. Nikzad^†, H. Yan, Y. Ochiai, J. Lai, Z. Yu, G. Chen, J. Kang, Z. Bao, High-energy density shape memory polymers using strain-induced supramolecular nanostructures, ACS Cent. Sci., 7, 1657-1667 (2021). 10.1021/acscentsci.1c00829

C.B. Cooper^†, J. Kang^†, Y. Yin, Z. Yu, H.-C. Wu, S. Nikzad, Y. Ochiai, H. Yan, W. Cai, Z. Bao, Multivalent assembly of flexible polymer chains into supramolecular nanofibers. J. Am. Chem. Soc. 142, 16814-16824 (2020). 10.1021/jacs.0c076515

C.B. Cooper, E.J. Beard, A. Vazquez-Mayagoitia, L. Stan, G.B.G. Stenning, D.W. Nye, J.A. Vigil, T. Tomar, J. Jia, G.B. Bodedla, S. Chen, L. Gallego, S. Franco, A. Carella, K.R.J. Thomas, S. Xue, X. Zhu, J.M. Cole, Design-to-device approach affords panchromatic co-sensitized solar cells. Adv. Energy Mater. 9, 1802820 (2018). 10.1002/aenm.201802820

C.B. Cooper, I.D. Joshipura, D.P. Parekh, J. Norkett, R. Mailen, V.M. Miller, J. Genzer, M.D. Dickey, Toughening stretchable fibers via serial fracturing of a metallic core. Sci. Adv. 5, eaat4600 (2019). 10.1126/sciadv.aat4600

C.B. Cooper, K. Arutselvan, Y. Liu, D. Armstrong, Y. Lin, M.R. Khan, J. Genzer, M.D. Dickey, Stretchable capacitive sensors of torsion, strain, and touch using double helix liquid metal fibers. Adv. Funct. Mater. 27, 1605630 (2017). 10.1002/adfm.201605630

^† denotes equal contribution