Organic Conjugated Polymers composed of Alternating Non-Fluorinated and Fluorinated Units: Novel Syntheses and Structure-Property Studies

This proposal describes plans to build on the recently established groundwork for the PI's long term goals of synthetic method development towards novel organic conjugated polymers and small molecules, structure-property relationships, molecular electronics, and environmentally benign processes. Intellectual Merit: (Liquid) crystalline and amorphous polymeric organic materials with defined arrangements of highly fluorinated (nF) and non-fluorinated (n) pi-electron-systems will be synthesized and subjected to structureproperty studies. The synthetic building blocks are chosen based on the well-known "soft" interactions between n and nF units as powerful supramolecular synthons, the ability to strongly alter bulk and molecular electronic properties through fluorine substitution, and clean (green) bond-forming reactions afforded by nF units. We have recently developed a transition-metal-free methodology to prepare alternating 1t-1tF conjugated polymers using only catalytic amounts of water-extractable additives. We will investigate the scope of this reaction to prepare other n-nF (het)arylene, (het)arylene-ethynylene, and (het)arylene-vinylene copolymers. The utility of the related Hiyama-type palladium-catalyzed coupling, which has seen few applications in polymer chemistry, will be investigated for the preparation of non-flourinated polymer analogues. The effect of regio-defined fluorine substitution will be delineated from the proposed library of polymers via structure-property studies using X-ray diffraction, optical microscopy, calorimetry, spectrophotometry, and simple electronic devices (e.g. LEDs). Broader Impact. The proposed study offers another step closer to the goal shared by burgeoning global R&D efforts towards low-cost organic electronics. Current potential market predictions for this class of materials continually inflate with each year. n-Type organic semiconductors are much more rare than their p-type counterparts, and there is much room for improvement of both types in terms of synthetic accessibility, performance, processability, stability, and purity in order to establish broad commercial viability. All of these points will be addressed by the projects proposed herein. Fluorination of arene units is shown to enhance electron injection from electrodes and subsequent transport while increasing oxidative stability, and alternating electon-rich and -poor repeating units can augment favorable (opto)electronic properties by increasing the quinoidal character of polymer chains. Two types of polymer reactions, including one as-yet undisclosed, will produce highly structurally pure polymers, minimalizing difficult-to-remove additives which can limit performance of final products. Choice and development of methodologies find their roots in the growing momentum of "Green Chemistry" in manufacturing processes. The technical contribution of this program will largely be in preparing the materials, determining structure-property relationships, and initial opto(electronic) characterization. These results will be disseminated widely via publications and presentations at interdisciplinary meetings, and collaboration from physicists and other materials chemists, both domestic and international (e.g. the PI's established European network) will be solicited, in order to establish cross-disciplinary ties and foster further development. The new synthetic methodology should find application is such other diverse fields as pharmaceuticals and catalyst ligands built from fluorinated arenes. Education. The University of Kentucky is ideally located to share in NSF's goal of increasing the participation of underrepresented peoples, in this case, the residents of Appalachia. The program proposed herein contributes to well-rounded education that empowers young scientists to take their next professional step, regardless of their chosen direction. Graduate and undergraduate students will develop technical proficiency in materials chemistry, and in communications and networking via written dissemination and presentation of results at interdisciplinary meetings. The PI will continue his contributions to the goal of the UK Dept of Chemistry to recruit young citizens of Appalachia by regularly visiting regional institutions to meet with the students and present the results of this work. The PI will partner with the Explorium of Lexington, a children's museum, to develop and implement handson activities and exhibits which convey basic chemistry/physics of polymers, organic electronic materials, and nanoscience. These activities will also be incorporated into the Explorium's "Trunk Shows", which are conducted away from the facility to reach the underprivileged that may not be able to visit the museum site. To convey to children that research leading to positive impacts on society and the environment can originate from them, the PI will also compile a "low-tech" rotating exhibit of simply written anecdotal biographical sketches of UK