(2km) Developing Approaches for Polymer Upcycling and Designing Sustainable Polymers

As is well-known, plastic waste is a growing environmental concern, with nearly 40% of end-of-life plastics ending up in landfills, and 20% being dispersed in the environment. Existing chemical recycling (depolymerization) strategies are energy-intensive and limited to only a fraction of the plastics in use. Mechanical recycling techniques often yield products with shorter lifetimes and deteriorated properties (‘down-cycling’). While significant progress has been made in the development of biodegradable materials, their widespread market adoption is impeded by their high cost and niche applications. In my independent research career, by I am to address these challenges by (i) developing energy-efficient depolymerization and upcycling strategies for plastics with notoriously low recycling rates (ii) adopting fundamental approaches to develop materials that are ‘designed to degrade’ under suitable environmental conditions.

In my Ph.D. research with Prof. Samanvaya Srivastava at the University of California, Los Angeles, I have been working on the fundamental and applied aspects of polymer science and chemical engineering. I worked on investigating the effect of non-idealities on polyelectrolyte (PE) complexation. It was revealed that the presence of divalent ions in solution leads to a reversal in phase composition, causing the selective retention of salt ions in the complex phase. Consequently, the retained divalent ions facilitate bridging between the PE chains thereby hindering chain relaxation. Further, length asymmetry between PE chains was shown to affect the salt resistance and viscoelastic properties of PE complexes. These studies have furthered our fundamental understanding of factors governing complexation in these systems, in addition to enabling tunability of PE complex composition and processability.

The second aspect of my graduate research has been focused on facilitating the circularity of one of the most used plastics in the world, polyurethane (PU) by adopting a dual approach–(i) reducing variability in recycling feedstock by a field-implementable, economic strategy (ii) upcycling chemolyzed PU products (polyols) into high-strength organic/inorganic composites. While this simple segregation strategy enables the development of recycling strategies tailored to each type of foam, engineering upcycled organic/inorganic composites provides an avenue for the complete utilization of polyols, which are otherwise employed as only a partial replacement to virgin feedstock. The covalently linked upcycled composites are lightweight and strong, as compared to ordinary Portland cement, while also demonstrating enhanced thermal insulation and acoustic attenuation than conventionally employed materials (e.g., gypsum). The physical (porosity, density), mechanical (flexural and compressive strengths), and functional properties (thermal and acoustic insulation) are strongly correlated with the nature of the polyol (OH-value, upcycled/virgin) and composition (inorganic and organic contents).

As an independent researcher, I aim to enable the development of (i) approaches for controlled mechano-chemical depolymerization and upcycling of plastics (ii) sustainable materials that are designed to degrade under suitable environmental conditions. In this dual pursuit, I look forward to harnessing my graduate research experience in the fundamental and applied domains of polymer systems. An understanding of the compositional and processing factors governing the properties of plastics will inform the design of depolymerization approaches and enable the prediction of the properties of upcycled products. The engineering of sustainable materials will be guided by a thorough investigation into degradable and cost-effective chemistries, without compromising the usable lifetime of these materials.

Selected Publications:

D. Iyer, M.T. Gallagher, D. A. Simonetti, G.N. Sant, S. Srivastava. “Hybrid Organic–Inorganic Composites Based on Glycolyzed Polyurethane.” ACS Sustain. Chem. Eng. 2022, 10 (51), 17116–17123.

D. Iyer, V. M. S. Syed, S. Srivastava. “Influence of Multivalent Cations on Phase Behavior and Rheology of Polyelectrolyte Complexes.” Journal of Polymer Science, 2021, 59 (22), 2895-2904.

D. V. Martínez Narváez, C. Wang, H. Sun, D. Iyer, S, Srivastava, Vivek Sharma. “Rheology of Particle Suspensions in Viscoelastic Fluid: Polymer Chemistry, Extensibility, and Particle-Polymer Interactions.” in preparation (as of July 2023).

D. Iyer, H. Senebandith, L. Willey, P. Goh, V. Huaco, S. Srivastava, “Effect of Length Asymmetry on Phase Composition and Viscoelasticity of Polyelectrolyte Complexes.” in preparation (as of July 2023).

Research Interests: Polymer upcycling, engineering degradable materials, designing and characterizing organic/inorganic composites.

Teaching Interests: Polymer science, characterization techniques for polymer and composite materials, transport phenomena