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)(2)Cl, Cp*Ru(PPh3)(2)Cl, [Cp*RuCl2](n), and [Ru(eta(3):eta(3)-C10H16)(mu-Cl)Cl](2) (Cp = cyclopentadienyl, Cp* = pentamethyl-Cp, and C10H16 = 2,7-dimethylocta-2,6-dicne-1,8-diyl) produce ester-functionalized poly(aroxycarbonylphenylene) (PACP) with high molecular weights (M-w up to 200 x 10(3)) in good yields (up to 90%). Topological structure of the polymer product can be hyperbranched or crosslinked, tunable by the extent of triple-bond conversion. The degree of branching (DB) of the PACP is similar to 0.76, much higher than those of the conventional hyperbranched polymers (DB similar to 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 hydrolysis reaction, and the collapse of its hyperbranclied skeleton rapidly releases the loaded molecules, showing promise as a drug carrier for missile therapy.