NSF Award
2203340
With the support of the Macromolecular, Supramolecular and Nanochemistry program in the Division of Chemistry, Professor Graham Collier of Kennesaw State University is developing a new approach for synthesizing conjugated monomers that will participate in numerous polymerization strategies and access a diverse class of semiconducting recyclable polymers. Semiconducting polymers are organic macromolecules in which a backbone of alternating single and multiple bonds results in pi-conjugation. This enables overlapping of molecular orbitals, which in turn allows for the delocalization of electrons. Following the doping process, the delocalized electrons become free to move around, resulting in an electrical current as they pass along the conjugated polymer backbone. Currently, conjugated polymers are the most important class of plastics used for optoelectronic devices such as LED screens in mobile devices and computers, solar cells, energy storage, sensors, and many others. However, many of the conjugated systems that meet performance metrics for these applications have complex structures, require multiple synthetic steps and generate toxic waste during polymerization protocols. This work addresses these issues and will focus on the synthesis of conjugated monomers in fewer synthetic steps from commercially available aldehydes, anilines and other biobased starting materials. Furthermore, the synthesis will be performed in the air and will not require extensive purification. The polymerization will also bypass commonly required cryogenic air- and water-free conditions. Beyond fundamental insights into the influence of monomer design on the polymer properties, degradable/recyclable copolymers also will be prepared. The advances in the synthesis of conjugated polymers that will be enabled by this research broadly support energy security by lessening demand on fossil fuel resources and employing less energy-intensive processing methods. This project will provide graduate and undergraduate students with training in polymer synthesis and macromolecular characterization techniques. Laboratory research will be complimented by efforts to develop upper division organic/polymer curriculum that will enable students to become familiar with fundamental concepts of macromolecular science, academic research, and how these are connected to societal problems. Synergistic research and education initiatives will provide opportunities for under-represented groups, especially African Americans, women, and first-generation students from rural North Georgia.<br/><br/>This research will focus on the development of modular, simple, and efficient synthesis of electron-rich pyrrolopyrroles for novel and tailorable conjugated polymers. In the first thrust, dihalogenated pyrrolo[3,2-b]pyrroles (H2DPP) will be prepared and incorporated into the main chain of conjugated polymers using direct heteroarylation polymerization. A strong focus will be placed on fundamental design and structure-property relationships such as optical, electrochemical, and thermal properties. The second thrust will center on the synthesis of degradable and recyclable H2DPP-based conjugated copolymers. This will be achieved by acid-catalyzed step-growth copolymerization of dialdehyde H2DPP with various diamines. Such strategy will eliminate the need for transition metal catalysts. More importantly, the resulting azomethine functional groups in the polymer backbone can readily be degraded by acid to their respective monomers. Outcomes from this work have the potential to provide fundamental information regarding new monomeric building blocks, develop simple polymers for sustainable approaches in organic electronics, and demonstrate the viability of H2DPPs in redox-active applications. The designed processes have high atom economy, are energy efficient and more environmentally benign than currently utilized methodologies.<br/><br/>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.
