Exploration of Effective Catalysts for Diyne Polycyclotrimerization, Synthesis of an Ester-Functionalized Hyperbranched Polyphenylene, and Demonstration of Its Utility as a Molecular Container with Implication for Controlled Drug Delivery

We present the first examples of a group of effective ruthenium catalysts for polycyclotrimerization. The polymerization reactions of an arylene bipropiolate monomer initiated by the Ru(II−IV) complexes of CpRu(PPh3)2Cl, Cp*Ru(PPh3)2Cl, [Cp*RuCl2]n, and [Ru(η3:η3-C10H16)(μ-Cl)Cl]2 (Cp = cyclopentadienyl, Cp* = pentamethyl-Cp, and C10H16 = 2,7-dimethylocta-2,6-diene-1,8-diyl) produce ester-functionalized poly(aroxycarbonylphenylene) (PACP) with high molecular weights (Mw up to 200 × 103) in good yields (up to 90%). Topological structure of the polymer product can be hyperbranched or cross-linked, tunable by the extent of triple-bond conversion. The degree of branching (DB) of the PACP is ∼0.76, much higher than those of the “conventional” hyperbranched polymers (DB ∼ 0.5). The PACP exhibits high transparency in the visible spectral region. It works as a molecular container, effectively trapping small molecules in its cavities with the aid of hydrogen-bond interaction. The polymer undergoes a bursting hydro...