Research

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The Kayser Laboratory is highly interdisciplinary, at the intersection of organic chemistry, polymer synthesis, and materials and device engineering. We develop innovative synthetic approaches and designs for polymeric materials, in particular organic electronics, that can address challenges in human health and sustainability.

Electronic materials integrated into biological systems have widespread potential in human health, including for fitness and health tracking, therapeutic electrostimulation to treat neurodegenerative diseases or nerve injuries, biosensing and electrophysiology, as instructive electrostimulation in tissue engineering, and for human-machine interfaces (actuators and prosthetics). But, the mechanical mismatch between “hard” electronics and “soft” biological tissues has prevented the widespread translation of bioelectronics due to discomfort, scarring, and/or device rejection in long-term applications. To solve this problem, we use organic electronics (π-conjugated polymers) because they have a higher flexibility and mechanical compliance than inorganic conducting (i.e., metals) and semiconducting materials (i.e., silicon). But, the use of organic electronics at biological interfaces brings additional challenges such as ionic conductivity, specificity, biodegradation, stability and adhesion under aqueous conditions, adaptability, and biocompatibility, that are often not considered. We therefore design materials for electronics, energy storage, and healthcare applications with these parameters as guiding principles.

We are using the toolbox of modern synthetic chemistry (photocatalysis, C-H activation, controlled radical polymerization, supramolecular chemistry) to control both the chemical structure and solid-state assembly of organic electronics from the molecular- to the macro-scale. Our group currently focuses on three main areas of research: (1) Electrically-conductive hydrogels; (2) Organic mixed ionic-electronic conductors; and (3) Upcycling plastic waste to functional polymeric materials.

hydrogels1. Electrically-conductive hydrogels. Electrically-conductive hydrogels could bridge the mechanical and electronic mismatch between biology and electronics. However, the composite approach taken to prepare them is inadequate for in vivo applications, because high conductivity can only be achieved at high loadings of conductive material, which significantly increases the elastic modulus and brittleness of the conductive hydrogel. To address this barrier to adoption, our group develops new conductive hydrogels with ultra-low elastic moduli and good conductivity. We are particularly interested in new approaches to process and pattern conductive hydrogels, such as by thermally-reversible gelation or photoprinting.

Representative publication: D. M. Nguyen, Y. Wu, A. Nolin, C.-Y. Lo, T. Guo, C. Dhong, D. C. Martin, L. V. Kayser*, “Electronically-Conductive Hydrogels by in-situ Polymerization of a Water-Soluble EDOT-Derived Monomer” Adv. Eng. Mater. 2022, 2200280.

PEDOTPSS rationale2. Organic mixed ionic-electronic conductors. Electrically-conductive polymers that can also transport and storage ionic charges (i.e., organic mixed ionic-electronic conductors, OMIECs) could play a major role in the study and treatment of human health conditions (electrophysiological and analyte sensing), in energy storage (batteries and capacitors), and flexible electronics (low power displays) by acting as transducers between ionic and electronic signals. However, current methods to functionalize these materials for specific applications and improved performance have been limited to blending with additives and side chain modification, which often decrease the electronic performance of the devices. Instead, we are working on a unique strategy which involves the self-assembly of block polyelectrolyte complexes to control the properties and functionality of OMIECs. In particular, our goal is to mimic key properties of biological systems, such as biodegradability (for transient electronics), specificity (for analyte-specific electronic biosensing), and adhesion in aqueous environments (for conductive tapes and improved stability of bioelectronics), while developing a better understanding of the fundamentals of OMIECs.

Representative publication: C.-Y. Lo, Y. Wu, E. Awuyah, D. Meli, D.M. Nguyen, R. Wu, B. Xu, J. Strzalka, J. Rivnay, D. Martin, L. Kayser*, “Influence of the Molecular Weight and Size Distribution of PSS on Mixed Ionic-Electronic Transport in PEDOT:PSS” Polym. Chem. 2022, 13, 2707.

upcycling3. Upcycling plastic waste to functional polymeric materials. The continuous production and accumulation of plastic waste poses a tremendous threat on the environment, society, and economy. With less than 10% of plastics being recycled, strategies to manage plastic waste and achieve a circular economy are critically needed. One of the most promising strategies is the upcycling of polymers to value-added polymeric materials by direct functionalization of the polymer backbone or side chains. Most reported chemical methods for upcycling plastics, however, are limited to energy-intensive processes with highly active reagents and a narrow scope of accessible products. Our group tackles these challenges by developing new catalytic reactions to functionalize aromatic plastic waste (e.g., polystyrene (PS), SEBS elastomers, PET). We have a particular expertise in the use of sulfonated/sulfinated polymers as reactive intermediates to “Click” new functional groups on the side chain of these polymers.

If you are interested in any of these projects and working in an interdisciplinary research team in a supportive and diverse environment, please visit this page or email Prof. Kayser directly for more details on available projects.

Funding

University of Delaware HensWEAR pilot project (completed) (PI: Kayser)

Center for Plastics Innovation EFRC seed grant (completed) (PI: Kayser)

University of Delaware – Argonne National Lab Seed Grant (June 2020 – May 2023) (PI: Kayser, co-PI: David Kaphan)

NIH COBRE Discovery of Chemical Probes and Therapeutic Leads supplement (August 2021 – July 2022) (PI: Kayser)

University of Delaware Research Foundation (UDRF) Award (June 2022 – May 2024) (PI: Kayser)

NIH COBRE Delaware Center for Musculoskeletal Research (DCMR) (May 2022 – Jan 2025) (PI: Charles Dhong, co-PI: Kayser)