Three-Step Synthesis of a Less-Aggregated Water-Soluble Poly(<i>p</i>‑phenylene ethynylene) with <i>Meta</i> Side Chains via Palladium/Norbornene Cooperative Catalysis

A three-step preparation of a highly water-soluble poly­(p-phenylene ethynylene) (PPE) from commercially available starting materials is disclosed. The palladium/norbornene-catalyzed AB–C-type polymerization has been developed, which enables installation of two piperazine meta side chains concurrently with the construction of the PPE backbone. The capability for double protonation of the piperazine moiety improves water solubility of this material. Compared to the PPE containing para side chains, the meta side chains reduce interchain aggregation and significantly enhance solubility and fluorescent quantum yields of the polymer