Synthesis of titanium-containing block, random, end-functionalized, and junction-functionalized polymers via ruthenium-catalyzed living radical polymerization and direct observation of titanium domains by electron microscopy

A series of well-defined titanium-containing random, diblock, and triblock copolymers were prepared by ruthenium-catalyzed living radical polymerization of glycidyl methacrylate followed by amination of the epoxy group with diethanolamine and titanium complex loading, which was achieved by reacting the resulting triethanolamine pendent group with CpTiCl₃ or CpTiCl ₃ (Cp: Cyclopentadienyl; Cp: pentamethylcyclopentadienyl). The titanium-containing unit obtained by this procedure possessed a discrete atrane structure, which contributed to the formation of soluble well-defined polymers without cross-linking via uncontrolled intermolecular multisite ligation to the titanium center. In addition, the Cp* derivatives were highly stable to moisture. The same strategy was used successfully to construct well-defined titanium end-functionalized polymers, and an epoxy-functionalized initiator was used in the ruthenium-catalyzed living radical polymerization of methyl methacrylate, followed by postreactions with diethanolamine and CpTiCl ₃. The titanium-containing block copolymers were analyzed by electron energy loss spectroscopy, transmission electron microscopy, and transmission electron microtomography to directly observe titanium-containing phases in the microphase-separated block copolymers.