Exploration of the Stille coupling reaction for the syntheses of functional polymers

The palladium-catalyzed Stille coupling reaction was used for preparing functionalized, conjugated polymers. This reaction has several advantages, two of which are that it requires mild reaction conditions and produces high yields. Several factors which affect the polymerization processes were investigated, such as the catalyst composition and concentration, different solvents and ligands, and structures of monomers. It was found that solvents that could keep the macromolecules in solution and stabilize the palladium(0) catalyst would yield polymers with high molecular weights. If a Pd(II) compound was used as the catalyst, a stoichiometric adjustment of the distannyl monomer was necessary to enhance the molecular weight of the resulting polymer. In general, it was found that a combination of an electron-rich distannyl monomer and an electron-deficient dihalide (ditriflate) monomer forms polymers with relatively high molecular weights. To further demonstrate the versatility of the Stille reaction for polycondensations, different types of conjugated polymers with different properties and applications, such as liquid crystalline conjugated polymers and conjugated photorefractive polymers, were synthesized.