CAREER: Block Polyelectrolyte Complexes for Controlled Mixed Ionic-Electronic Conduction

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This project is jointly funded by the DMR Polymers Program and the Established Program to Stimulate Competitive Research (EPSCoR). PART 1: NON-TECHNICAL SUMMARYThe use of electronic materials and devices at biological interfaces (i.e., bioelectronics) enables important applications in human health, such as for electrostimulation (e.g., to treat Parkinson’s or Alzheimer’s disease), biosensing, nerve/wound healing, and electrophysiological measurements. But, most common electronics in everyday devices are made of precious metal conductors, such as gold or platinum. These materials are not ideal for applications related to human health because they are too rigid and brittle. They also use electrons for communication instead of ions like biological systems do (e.g., neurons communicate through differences in ion concentration); this makes it difficult to “translate” electronic signals to ionic ones for stimulation, or vice versa for sensing. To address these problems, new materials are needed that are much softer, biocompatible, and enable the conduction of both electrons and ions. This research will introduce a new class of polymers that fit these criteria and have properties inspired from biology. These electron- and ion-conducting polymers will be synthesized, characterized and integrated in devices, to provide design rules to optimize the efficiency of electronic materials specifically made for bioelectronics applications. This research will therefore have an impact in both fundamental research on materials and applications in healthcare. It will also provide educational activities, hands-on demonstrations, and a mentoring program designed to broadly educate about the uses of polymeric materials and trigger and nurture interest in materials science and engineering. These educational, outreach, and research activities will actively engage graduate and undergraduate students to help develop their capabilities as interdisciplinary researchers, and thereby also increase the participation and retention of marginalized students.PART 2: TECHNICAL SUMMARYElectrically-conductive polymers that can also transport ions (i.e., organic mixed ionic-electronic conductors) could play a major role in the study and treatment of neurological disorders by acting as transducers between ionic and electronic signals. However, current methods to functionalize these materials for bioelectronic applications have been limited to blending with additives and to side-chain modification, which often decrease the electronic performance of the devices. The goal of the planned research is therefore to access organic mixed ionic-electronic conductors that maintain or improve their electronic performance upon functionalization with an electronically-insulating polymer. To achieve this goal, the complexation between neutral-anionic diblock copolymers and positively-charged conductive polymers (i.e., block polyelectrolyte complexes) will be leveraged to control the ordering of otherwise disordered mixed conductors, and ultimately tailor their properties for applications specific to bioelectronics. These block polyelectrolyte complexes will mimic key properties of biological systems while precisely controlling the relative contribution of ionic and electronic transport and ionic-electronic coupling. The research will focus on mimicking three biological properties: (1) specificity, (2) dynamic and adaptable properties, and (3) biodegradability. The results of this research will enable new functionalities for bioelectronic devices (e.g., ion-selective sensors, injectable and conductive tissue scaffolds, and transient devices), and contribute to the establishment of fundamental molecular design rules for high performance organic mixed ionic-electronic conductors. This research will also integrate educational activities for students and parents about the positive societal impact of functional plastics, in particular plastic electronics. A laboratory module will be developed to introduce junior undergraduate students to authentic research in organic electronics. The samples produced during this laboratory will be used in an outreach module on plastic electronics for K-12 students. This grant will also support the creation of a mentoring and support network for high school girls interested in pursuing a college degree in materials science and engineering.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.