Investigation of PEPPSI precatalysts for controlled polymerization of -conjugated polymers from cheap starting materials

Abstract

Since the discovery of catalyst-transfer polymerization in 2004 there has been significant research into expanding the scope from Kumada couplings of poly-thiophenes mediated by nickel initiators. This thesis presents an investigation toward the synthesis of -conjugated polymers by the elusive pseudo-living polymerization of chloroarene monomers. Chapter 1 sets the scene with an in-depth review of chain-growth polymerizations mediated by palladium catalysts. In chapter 2, we report the first examples of exhaustive substitution of poly-chloroarenes in the presence of a deficit of nucleophile in the sp3-sp2 Negishi coupling mediated by PEPPSI-IPr. These experiments demonstrated intramolecular transfer of the active catalyst which is essential for catalyst-transfer polymerization. Chapter 3 describes the synthesis of the highly active PEPPSI-IPent precatalyst from cheap commercially available starting materials with minimal purification. Subsequently in chapter 4, it was demonstrated that PEPPSI-IPent undergoes exhaustive substitution of poly-chloroarenes in the presence of a deficit of nucleophile in sp2-sp2 Kumada, Negishi and Suzuki cross-couplings. In chapter 5, optimization of current Kumada polymerization of bromo phenylene-based monomer mediated by PEPPSI-IPr is described. Direct comparison of model reactions and Kumada polycondensation confirmed high selectivity for exhaustive substitution is required to achieve polycondensation in a chain-growth manner. Initial research into catalyst-transfer polycondensation of chloroarene monomers did not achieve polymerization in a chain-growth manner using modified conditions from bromoarene monomers.