Project:	Chemical Upcycling of Polyolefins Into Functionalized Polyolefin
Disciplines:	Chemistry, Chemical Engineering, Materials Science
Mentor:	E. Bryan Coughlin, Professor, (CCE), coughlin@mail.pse.umass.edu, Phone: 413-577-1616
Mentor URL:	https://www.umass.edu/polymer-science/about/directory/e-bryan-coughlin  (opens in new window)
Background:	NOTE: This project is being offered by a Caltech alum and is open only to Caltech students. The project will be conducted at the University of Massachusetts Amherst in Amherst, Massachusetts. Multiple strategies are required to address the mounting issues of plastic waste and climate change. We propose to transform polyolefins, including polyethylenes with various chain architectures and isotactic polypropylene, into higher-value functionalized polyolefin copolymers. In contrast to polymer deconstruction into smaller molecules, this strategy aims to maintain high molecular weights during the chemical transformations. To attain commercial significance, specialty polyolefins often have just 2-6 mol% of monomeric units with hydroxyl, carboxylic acid, or ester functionalities. We are targeting functionalized polyolefins with similar compositions and a wider range of functionalities. By starting from polymer feedstocks rather than petroleum-based feedstocks, we intend to reduce the energy consumption and greenhouse gas emissions needed to deliver these valuable polymers.
Description:	We propose a variety of synthetic strategies to install functional groups onto polymers with minimal molecular weight change. Our team includes experts in homogeneous/heterogeneous catalysis, reactor design, organic and polymer chemistry, and polymer physics. In Aim 1, we propose partial dehydrogenation of the saturated polymers followed by functionalization of the C=C bonds. Building upon our recent findings, we will design and evaluate Ru and Os catalysts for dehydrogenation and will also initiate a new line of inquiry using tandem halogenation/elimination catalysis for dehydrogenation of polyolefins. Having recently demonstrated that thiol-ene click chemistry can install hydroxyl or carboxylic acid groups, we will extend this method to acetate, amine, and novel mixed functionalities. Additional strategies to functionalize the C=C bonds include epoxidation, dihydroxylation, hydrocarboxylation, and hydroesterification. In Aim 2 we focus on direct polymer-to-polymer conversion via metal C-H activation. We will design and build a high-pressure flow reactor to evaluate heterogeneous catalysts and work to understand how interfacial interactions and confinement effects impact polymer adsorption/desorption rates and reaction kinetics. Also, we will study homogeneous catalysts with oxygen for hydroxylation, and with carbon monoxide for carboxylation. Aim 3 explores photochemical methods for C-H cleavage for direct functionalization of polyolefins. Preliminary results using nickel catalysts are promising for carboxylation, and we will also investigate acrylation and Minisci reactions. Reaction pathways and kinetics will be studied, both computationally and experimentally, to inform our design of new catalysts and guide the reaction optimization. We will soon have a new high temperature GPC to evaluate the extent to which our synthetic methods maintain polymer architecture and molecular weight. We will characterize the physical properties of the functionalized polymers emphasizing the valueadded properties of toughness, adhesive strength, and oxygen permeability associated with functionalized polyethylene copolymers. Given the limitations of sorting post-consumer plastics and the inherent complexities of multilayer plastic packaging, we will develop our functionalization chemistries for single and mixed plastics. We will evaluate our hypothesis that the associating groups installed on the polyolefins will promote blend compatibilization for improved properties (Aim 4).
References:	“Incorporation of Thioacetate Pendants on a Polyalkenamer Enables High Extensibility” Roshni John Chethalen, Myounguk Kim, Juan Correa Ruiz, Chien-Hua Tu, Jordan Gray, Karen I. Winey, Alan J. Lesser, Alfred J. Crosby, E. Bryan Coughlin Macromolecules 2024, 2024, 57, 21, 10358–10367 https://doi.org/10.1021/acs.macromol.4c02110 “Modulating the Contact Angle between Nonpolar Polymers and SiO2 Nanoparticles” Anirban Majumder, Anne N. Radzanowski, Ching-Yu Wang, Yijiang Mu, E. Bryan Coughlin, Raymond J. Gorte, John M. Vohs, Daeyeon Lee Macromolecules 2024, 57, 8554–8561 https://doi.org/10.1021/acs.macromol.4c00823 “Coupling and Decoupling between Stickers and Backbones in Associating Polymers with Terminally Functionalized Side Chains” Chien-Hua Tu, Eli J. Fastow, Roshni John Chethalen, George V. Papamokos, E. Bryan Coughlin, Karen I. Winey Macromolecules 2024, 57, 8067–8081 https://doi.org/10.1021/acs.macromol.4c00983 “Hydrocarboxylation of C═ C Bonds in Polycyclooctene: Progress Toward Valorization of Waste Polyolefins” Ikechukwu Martin Ogbu, Eli J Fastow, Weihao Zhu, Lucille A Wells, Roshni J Chethalen, Vivek Nair, Zachary R Hinton, Alex H Balzer, Weiguo
Student Requirements:	First-year general chemistry, some organic chemistry knowledge is preferred but not required. Solid math skills, as all Caltech students have. No prior research experience required.
Programs:	This AO can be done under the following programs:   Program    Available To        SURF    Caltech students only  Click on a program name for program info and application requirements.