(4n) From Tackling Plastics Waste to Designing Better Electric Cars: Engineering Transport Processes in Soft Materials to Advance the Sustainable Economy

Overview: I am interested in using chemical engineering principles to engineer technologies that will accelerate our path to a cleaner future. The success of many of these technologies and their ability to replace traditional fossil fuel-hungry options are limited by problems of dynamics. E.g. the motion of lithium ions through a polymer electrolyte is so slow that the electrolytes cannot be deployed in solid-state batteries despite offering safety and higher capacity benefits. Addressing such problems requires understanding the factors controlling the transport processes in these systems. I am interested in advancing our understanding of nanoscale transport processes in soft materials to improve the performance of sustainable technologies. With my expertise in nanoscale characterization, polymer physics, rheology, and interfacial sciences, I want to build a multidisciplinary research program that addresses rate-limiting transport processes in clean energy, upcycling, and additive manufacturing domains.

Research Interests

Many technologies we build to mitigate and adapt to climate change utilize a class of materials called soft matter. This diverse class includes colloids, polymers, liquid crystals, surfactants, etc. find use in many promising clean energy, human health, and additive manufacturing technologies. Addressing the climate crisis requires the development of not just high-performing soft materials but also the engineering of greener manufacturing processes and a consideration of their after-use life. The performance of these materials and the efficiency of their manufacturing and end-of-life disposal processes depend on nanoscale transport processes. For example, the rate of ion transport dictates the performance of polymer electrolytes, transfer of heat/sound through materials is controlled by molecular relaxation processes, dissipative processes dictate the mechanical properties of tissue-mimicking materials, and the rate of access of active sites limits the performance of heterogeneous catalysts in upcycling of plastics.

In addition to the chemical identity of materials, physicochemical aspects arising out of nanoscale processing such as capillarity, presence of interfaces, etc. modulate intermolecular interactions and therefore, serve as tools to control dynamics. Armed with the principles of nanoscale engineering and molecular design, I will develop a research program to ‘understand and control transport processes in soft materials’. The guiding approach of our research activities will be to probe soft matter dynamics to understand how molecular design and nanoscale processing control the dynamic properties and use this insight to design high-performing materials and sustainable processes. The questions we ask will be placed at the confluence of polymer physics, interfacial engineering, and rheology. Projects will involve a diverse range of activities such as nanomaterial/polymer synthesis and processing and utilizing/building nanoscale rheological characterization tools for measuring polymer motion, ion transport, and small molecule diffusion.

Specifically, I organize my research activities in these three thrusts:

1. Understanding transport limitations in reacting polymeric systems and developing ways to reduce mass transfer resistance for advancing catalytic upcycling of waste plastics
2. Studying ion transport in charged systems with the goal of achieving superior lithium transport rates in battery electrolyte applications
3. Elucidating molecular origins of rheological and interfacial properties of coacervates for developing bio-sourced inks for additive manufacturing

Postdoctoral research (Advisor: Rachel Segalman, University of California Santa Barbara)

Nanoscale characterization techniques are needed to evaluate the performance of upcycling catalysts as batch-scale measurements inflate the scission kinetics arising from unselective cleavage by mechanical forces in the reactors. I developed a method to track the scission rates of polymer inside pre-filled nanopores using dielectric spectroscopy. We demonstrated that the evolving segmental dynamics of polymers undergoing scission inside pores are indicative of the rate of scission processes inside catalytic pores. Additionally, I am also using electrochemical characterization techniques to evaluate zwitterionic chemistries for application as battery electrolytes.

Doctoral research (Advisor: Daeyeon Lee, University of Pennsylvania)

Thesis: Polymer dynamics in disordered nanoparticle packings – effect of confinement, interfaces, and humidity

I developed a room-temperature process to confine polymers in the pores of close-packed nanoparticle packing using capillary forces. Utilizing the tunability of pore size, I studied the effect of nanoconfinement on entangled polymer dynamics and showed that the chain motion and the segmental motion can be altered in conflicting ways by confinement. Additionally, the hydrophilic nature of the nanoparticles was utilized to examine the effect of condensed water on polymer dynamics in nanopores. This study highlighted that adsorbed water layers on particles can reduce the segmental friction experienced by the chain.

Teaching Interests

As a teaching assistant for two introductory courses in the chemical engineering curriculum (energy and mass balances & heat and mass transport) offered to sophomore undergraduate students, I got first-hand experience of the joys and challenges of teaching. These introductory courses can shape a student’s experience of the program and open their minds to the possibilities of a chemical engineering degree. The instructor and I designed the curriculum such that effective classroom teaching was complemented by real-world examples in recitation hours, problem sets that stressed on applications, and demo/lab activities that helped further illustrate the concepts taught. It was gratifying to see our activities benefit the class of 60+ students who not only fared well in the exams/problem sets but also reported in later years that they were continuing to use these concepts in their advanced courses at Penn.

During the pandemic, I also got an opportunity to teach high school students the ‘basics of surface sciences and capillarity’ over zoom. This was part of an outreach event to introduce local high schoolers in the Philadelphia area to the scientific concepts used in Penn’s labs involving activities that can be completed using items found around their house. It was illuminating to see advanced concepts like surface tension, intermolecular interactions, capillary rise, etc. be distilled down to the basics in a fun and informative way. This experience introduced me to the techniques involved in effective classroom teaching.

My experiences reinforce my beliefs on what the goals of an educator should be – to impart knowledge, teach students how to learn, and encourage them to think critically and creatively. Through my career as a professor, I would direct my activities to achieve these goals such that I can help create the next generation of thinkers and leaders. I plan to achieve this by: designing courses where learning goals are tied to real-world applications, fostering a learning classroom environment, and ensuring that learning barriers are removed to improve student engagement.

I am interested in teaching core courses on transport phenomena and thermodynamics at the graduate and undergraduate levels and electives in nanoscale engineering, polymer physics, soft matter, and interfacial phenomena. I am also keen on designing new experiential learning courses based on non-linear rheology of soft materials, sustainable consumer product development, and upcycling of general waste streams. To further the education mission, I will help recruit and train diverse scholars, organize professional development events for students, and contribute to the department’s outreach activities.

Select Publications (5 out of 11)

1. Venkatesh RB, Bingaman J, Scott S, Walker L, Segalman R. Dielectric spectroscopy as a tool to monitor pore-scale chain scission processes for upcycling catalyst design. In preparation
2. Venkatesh RB, Lee D. 2022. Interfacial Friction Controls the Motion of Confined Polymers in the Pores of Nanoparticle Packings. Macromolecules, 55(19), 8659-8667
3. Venkatesh RB, Lee D. 2022. Conflicting Effects of Extreme Nanoconfinement on the Translational and Segmental Motion of Entangled Polymers. Macromolecules, 55(11), 4492–4501
4. Venkatesh RB, Zhang T, Manohar N, Stebe KJ, Riggleman RA, Lee D. 2020. Effect of polymer-nanoparticle interactions on solvent-driven infiltration of polymer (SIP) into nanoparticle packings: A molecular dynamics study. Molecular Systems Design & Engineering, 5(3), 666–74
5. Venkatesh RB, Han SH, Lee D. 2019. Patterning polymer-filled nanoparticle films via leaching-enabled capillary rise infiltration (LeCaRI). Nanoscale Horizons, 4(4), 933–39