(2hk) Multi-Scale Processing of Architecturally Complex Polymer Materials | AIChE

(2hk) Multi-Scale Processing of Architecturally Complex Polymer Materials

Research Interests

There is a long-standing goal to connect the molecular-level structure and dynamics of polymers to bulk material behaviors. The structure and dynamics of polymer materials are dictated by molecular-level details such as their constituent chemistry, molecular size, chain architecture, and surrounding environment. However, polymer materials are frequently subjected to processing conditions (e.g., flow, temperature annealing, and/or electric fields), which can significantly alter their bulk properties due to changes in polymer microstructure. Despite this known interplay of microstructure and bulk properties, few characterization techniques facilitate the bridging of molecular to macroscopic properties during processing. I am interested in the design of precise polymer materials and development of in situ characterization tools to unify our understanding of polymers across the entire spectrum of length scales. Establishing this multi-scale understanding of polymer dynamics will inform molecular design strategies to meet the needs of areas such as sustainability, human health, and the environment.

As a faculty member, I will build upon my graduate training in experimental nonlinear rheology and constitutive modeling and my postdoctoral work on the molecular design of architecturally complex polymers to engineer polymer materials for sustainability, human health, and the environment. Initial areas of my research program include single-molecule rheology of entangled polymer mixtures, responsive bio-hybrid hydrogel materials, and gel polymer electrolytes for next-generation energy storage applications. Each of these focus areas will provide opportunities to design precise polymers, engineer their assembly, develop tools for multi-scale materials characterization, and refine the molecular design to tailor material properties.

Research Experience

Molecular engineering of complex polymer architectures for human health and sustainability, Department of Chemical Engineering, Stanford University (advised by Danielle J. Mai)

As an Arnold O. Beckman Postdoctoral Fellow, the general theme of my research is molecular-level design of architecturally complex polymers. In one project, I seek to understand how the “bottlebrush” shape of biopolymers (e.g., lubricin and mucin) results in the superior (bio)lubrication observed within the human body. To do this, I have developed a hybrid biosynthetic approach that combines “graft to” and “graft from” strategies used by synthetic polymer chemists to create bottlebrush polymers. This hybrid approach facilitates the preparation of model bottlebrush DNA polymers with precise backbone/side chain lengths and side chain grafting densities for direct single-molecule visualization in lubrication flows using fluorescence microscopy. In another project, I aim to significantly reduce single-use plastic waste by engineering reversible polymeric materials. I am studying how end-functionalized multi-arm star polymers can be leveraged for photochemistry-mediated recyclable 3D printing. As part of this work, I designed a rheo-optical setup which allows for dynamic rheological characterization during irradiation with light wavelengths that trigger either “printing” or “erasure”. By preparing star polymers of different molecular weights and numbers of arms per star, I discovered that fewer arms per star results in slower printing speeds, but faster erasure compared to star polymers with more arms. In using these well-defined polymers, I have advanced molecular design rules for polymer resins in sustainable 3D printing applications.

Flow-concentration coupling of entangled polymer liquids, Department of Chemical Engineering, UC Santa Barbara (advised by Matthew E. Helgeson and L. Gary Leal)

During my Ph.D., I developed an expertise in the flow-based processing of polymers. Entangled polymers are highly viscoelastic materials that exhibit shear rate dependent viscosities, which can vary by orders of magnitude depending on the applied shear rate. These changes to fluid viscosity are connected to a flow-induced fluid microstructure that standard rheological measurements alone cannot measure. To study the coupling of polymer microstructure and rheology, I developed rheo-optical methods to quantify the polymer concentration and flow fields, complementing standard rheological measurements. My work resulted in the first experimental measurements that confirmed a theoretically predicted flow instability, which arises from a coupling of flow to concentration. I discovered that strong departures from a uniform velocity profile develop across sheared entangled polymer solutions and coincide with macroscopic changes to the polymer concentration profile. In comparing experimental data with theoretical model predictions, I helped resolve a longstanding disagreement between the flow behavior of chemically disparate entangled polymer solutions. These advanced rheo-optical measurements revealed that macroscopic changes to polymer concentration develop in flow and underscored the importance of accounting for concentration heterogeneities in sheared polymeric liquids. This implied need to account for concentration heterogeneities represents a paradigm shift in the development of constitutive models and multi-faceted characterization methods for complex fluids.

Selected Publications:

  • M. C. Burroughs, L. Nieman, L. X. Wang, D. J. Mai, (2023), in prep.
  • M. C. Burroughs, E. L. Quirk, B. M. Wirtz, T. H. Schloemer, D. N. Congreve, D. J. Mai, (2023), in prep.
  • Q. Zhou, B. M. Wirtz, T. H. Schloemer, M. C. Burroughs, M. Hu, P. Narayanan, J. Lyu, A. O. Gallegos, C. Layton, D. J. Mai, D. N. Congreve, “Spatially controlled UV light generation at depth by upconversion micelles”, (2023), in review.
  • M. C. Burroughs, T. H. Schloemer, D. N. Congreve, D. J. Mai, “Gelation dynamics during photocrosslinking of polymer nanocomposite hydrogels”, ACS Polymers Au, 3, 217–227, (2023).
  • M. C. Burroughs, Y. Zhang, A. M. Shetty, C. M. Bates, M.E. Helgeson, L. G. Leal, “Flow-concentration coupling determines features of nonhomogeneous flow and shear banding in entangled polymer solutions”, Journal of Rheology, 67, 219–239, (2023) *Featured article
  • M. C. Burroughs, Y. Zhang, A. M. Shetty, C. M. Bates, L. G. Leal, M. E. Helgeson, “Flow-induced concentration nonuniformity and shear banding in entangled polymer solutions”, Physical Review Letters, 126, 207801, (2021).
  • M. C. Burroughs, A. M. Shetty, L. G. Leal, M. E. Helgeson, “Coupled non-homogeneous flows and flow-enhanced concentration fluctuations during startup shear of entangled polymer solutions”, Physical Review Fluids, 5, 043301, (2020).
  • P. Cheng, M. C. Burroughs, L. G. Leal, M. E. Helgeson, “Distinguishing shear thinning from shear banding in flows with a stress gradient”, Rheologica Acta, 56, 1007–1032, (2017).
  • M. C. Burroughs*, S. M. Bhaway*, P. Tangvijitsakul, K. A. Cavicchi, M. D. Soucek, B. D. Vogt, “Cooperative Assembly of Metal Nitrate and Citric Acid with Block Copolymers: Role of Carbonate Conversion Temperature on the Mesostructure of Ordered Porous Oxides”, Journal of Physical Chemistry C, 22, 12138–12148, (2015). *indicates co-first author

Selected Awards:

  • Arnold O. Beckman Postdoctoral Fellowship in the Chemical Sciences (2022 – 2024)
  • University of Washington, Distinguished Young Scholars Seminar Speaker (2023)
  • ACS Polymeric Materials Science and Engineering Future Faculty Scholar (2023)
  • Stanford Bio-X Travel Award (2023)
  • APS Future Investigator Travel (FIT) Award (2023)
  • NSF Graduate Research Fellowship, Honorable Mention (2016, 2017)
  • Senior Award for Scholarly Achievement, NC State University Department of Chemical and Biomolecular Engineering (2015)

Teaching Interests

Given my educational background in chemical engineering, I am qualified to teach all chemical engineering undergraduate and graduate core courses. I especially look forward to teaching transport phenomena, material and energy balances, and thermodynamics. Beyond core chemical engineering courses, I am interested in developing two new elective courses: (i) a consumer products formulations course that introduces students to relevant material properties in the engineering of soft materials, and (ii) a rheology course focused on measurement techniques and characterization of functional materials.

My role as an educator extends beyond the classroom into the research lab. I am committed to training researchers from all career stages and backgrounds in an interdisciplinary research environment focused on polymer science and engineering. In fulfillment of this vision, projects in my group will utilize concepts from chemical engineering, materials science, physics, chemistry, and synthetic biology.

Teaching Experience

During graduate school, I served as a teaching assistant for several different chemical engineering courses including:

  • ChE 180 – Senior Unit Operations Lab
  • ChE 10 – Material and Energy Balances
  • ChE 220B – Graduate Transport Phenomena

Each of these experiences afforded me opportunities to grow as an educator. In addition to TA duties, I was given several opportunities to guest lecture ChE 10 classes. I also worked with John Wiley & Sons to develop and proofread a solutions manual for the 4th edition of “Elementary Principles of Chemical Processes” by Felder, Rousseau, and Bullard.

Service

I am committed to fostering a diverse, equitable, and inclusive environment in the classroom, research lab, and broader scientific community. This commitment has guided my continued participation in service and outreach activities for over a decade. At UC Santa Barbara, I co-founded a Graduate Student Association (GSA) for the Chemical Engineering department, which organized social and professional development activities for students. In graduate school, I chaired the planning of our department’s 12thannual Amgen-Clorox Graduate Student Symposium. At UC Santa Barbara and Stanford, I have organized a weekly seminar series for researchers and faculty in the chemical sciences to build on-campus community, provide scientific communication training opportunities, and catalyze interdisciplinary research activity. Since graduate school, I have continuously engaged in K-12 outreach at local elementary, middle, and high schools. I am a firm believer in the importance of early exposure to STEM in the recruitment of future students from diverse backgrounds and identities. As a faculty member, I will continue to engage in service and outreach activities on lab, university, and scientific community levels.