Abstract:

Conjugated polymers are traditionally synthesized with targeted properties in mind while sustainable considerations or green chemistry principles can be overlooked. As a means to minimize waste, reduce the number of synthetic steps, and use safer reagents, pyrrolo[3,2-b]pyrroles (DHPPs) are explored as novel building blocks for synthesizing conjugated polymers. DHPPs are excellent candidates for this because monomers are accessible in one synthetic step from commercially relevant starting materials (anilines and aldehydes), monomer synthesis is performed in air, and purification does not require chromatography. Dihalogenated DHPP comonomers are easily synthesized and readily participate in metal-catalyzed cross-coupling reactions and polymerizations to obtain a family of highly tailorable chromophores and polymers. Fundamental design-structure-property relationships are established by studying synthesized polymers with optical, electrochemical, and thermal characterization techniques. Beyond fundamental studies, this family of polymers demonstrates their utility in redox and solid-state applications, evident by functioning as high-contrast electrochromes or active-layer material in organic photovoltaics. The synthetic complexity of resulting polymers also is determined and utilizing DHPPs yields alternating copolymers with synthetic complexities lower than more commonly studied analogues. Outcomes from this work provide a simpler approach for synthesizing conjugated polymers while maintaining tailorability and functionality in device-inspired measurements and motivates further utilization of electron-rich pyrrolopyrroles in organic electronics.

Bio:

Graham, originally from Fayetteville, NC, received his B.S. in chemistry in 2011 from the University of North Carolina Wilmington. Upon graduation, Graham enrolled in the Master of Science program at the University of North Carolina at Charlotte and studied porphyrin chromophores under the direction of Dr. Michael Walter. After graduating in 2013, Graham enrolled in the chemistry Ph.D. program at the University of Tennessee-Knoxville with a concentration in polymer chemistry. Graham’s dissertation entailed studying structure-property relationships of purine-based polymers and chromophores under the guidance of Dr. Mike Kilbey. Graham received his Ph.D. in 2017 and began his position as Postdoctoral Research Associate at Georgia Tech studying conjugated polymers for electrochromism under the mentorship of Dr. John Reynolds. Graham joined the faculty at Kennesaw State University as an Assistant Professor in the Fall of 2020.