Branched polyphenylenes have attracted interest because of their shape-persistance and because they serve as precursors of functional pi-electron systems with extensive conjugation. While para-linked polyphenylenes are typically accessed through Pd-catalyzed cross-coupling polymerizations, these reactions have shown low efficiency for forming ortho-linked polyphenylenes. Thus, ortho-polyphenylenes have been mostly limited to a few reports of oligomeric materials. We have developed a method to incorporate ortho-phenylene linkages into high molecular weight conjugated polymers through a benzannulation reaction at each carbon-carbon triple bond of poly(phenylene ethynylene)s (PPEs). This approach is particularly attractive because PPE polymerization is well established and offers significant structural versatility, and modifications of the PPE alkynes are relatively rare. We will show that this cycloaddition reaction occurs along the polymer backbone with high efficiency. The optical and electronic properties of the resulting poly(phenylenes) will be discussed, as well as preliminary results towards their oxidative planarization to graphene nanoribbons.

Highly efficient benzannulation of poly(phenylene ethynylene)s

244th National Meeting (2012)

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