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
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Abstract
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 CpTiCl<sub>3</sub> or Cp*TiCl<sub>3</sub> (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 Cp*TiCl<sub>3</sub>. 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