KSEF R&D Excellence: Highly Cost-Effective and Environmentally Benign Synthesis of Organic Materials for Consumer Micro-Electronics

Herein we propose to investigate the scope of novel carbon-carbon bond forming reaction which is particularly well-suited to the preparation of organic conjugated polymers. The coupling reaction occurs between silyl-functionalized monomers, in which the silicon group is attached to sp and Sp2 carbons, and highly fluorinated arenes. With each new bond-formation, the reagent which induces the reaction (fluoride ion) is regenerated. The reaction therefore proceeds to high yields producing high-molecular weight polymers, requiring only a minute (catalytic) amount of fluoride additive. Chemically pure polymers are produced with well-defined end-groups. High purity is also possible because the fluoride ion source and the sole side product (a gas) are very easily removed. The reaction is a highly attractive alternative to transition-metal catalyzed reactions which currently dominate the field. The viability of the method to prepare a number of classes of technologically relevant conjugated polymers will be investigated. These include alternating copolymers of thiophene derivatives, poly(arylene ethynylene)s, and poly(arylene vinylene)s. Practical syntheses of all requisite silane-functionalized monomers are outlined. To facilitate the delineation of the reactivity of each new monomer, model studies will be conducted to prepare small molecules which may more easily be characterized by standard techniques, thus gaining more reliable proof of the efficacy of the reaction. Since nearly all of the materials proposed herein are without precedent, structure-property studies will also be conducted to evaluate the effect of a perfectly-alternating structure on thermal, optical, and self-assembly properties. Methods to be used in these structure-property studies are wide-angle x-ray diffraction, thermal polarized optical microscopy, differential scanning calorimetry, thermo gravimetric analysis, and standard spectroscopic techniques including absorption and emission spectroscopy. In an iterative approach, new polymers will be designed with differing side-chains in order to engineer these properties. The materials chosen for this study all have promise as low-cost active components in consumer electronics. The presence of perfluoroarene groups has already been demonstrated to positively affect the properties of small molecule semiconductors. However, prior attempts at polymers similar to those proposed here failed to show any great benefit. In some cases, very poor solubility precluded evaluation, while others used synthetic methods leading to ill-defined structures. The cleanliness of the method proposed herein, together with a systematic plan to vary substituents until soluble polymers are obtained, guarantees that the study will provide materials leading to an understanding of the effect of fluorination on the properties of conjugated polymers. Given the broad interest in functionalized, highly fluorinated aromatics in such diverse fields as ligands for transition-metal catalysts and pharmaceuticals, the proposed research is expected to stimulate interdisciplinary progress.