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 Cp*TiCl₃ (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*TiCl₃. 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

Epitaxial Phase Transition between Double Gyroid and Cylinder Phase in Diblock Copolymer Thin Film

The epitaxial relationship in the thermal phase transition between double gyroid (DG) and hexagonally packed cylinder (HEX) phases in polystyrene-<i>block</i>-polyisoprene thin films on Si wafer was investigated using transmission electron microtomography and grazing incidence small-angle X-ray scattering. Two different types of epitaxial transitions were observed, and they appeared to be selectively favored depending on the transition direction. One type of epitaxial relationship prevails in the phase transition from DG to HEX upon heating in which {121}_DG, {111}_DG, and {220}_DG are converted to {100}_HEX, {110}_HEX, and {001}_HEX, respectively. The interphase planes are {220}_DG and {001}_HEX, and the cylinders meet the {220}_DG plane perpendicularly (head-on, Type A) at the grain boundary between DG and HEX. Although there are small dimensional mismatch and distortion in the location of the cylinders in this epitaxial relationship, all cylinders are formed along the topologically equivalent DG skeletal path. On the other hand, in the transition from HEX to DG upon cooling, another epitaxial relationship as well as the head-on type epitaxy was observed, in which {100}_HEX, {110}_HEX, and {001}_HEX are converted to {121}_DG, {220}_DG, and {111}_DG, respectively. The interphase planes are {220}_DG and {110}_HEX, and the cylinders meet the {220}_DG plane in parallel (side-on, Type B) at the grain boundary between HEX and DG. The domain spacing and the symmetry of the two phases are matched near perfectly, but cylinders are converted to two different DG skeletal paths. The Type B epitaxy is hardly observed in the transition from DG to HEX

Morphological Control of Helical Structures of an ABC-Type Triblock Terpolymer by Distribution Control of a Blending Homopolymer in a Block Copolymer Microdomain

The control of microphase-separated structures in a poly­(styrene-<i>block</i>-butadiene-<i>block</i>-methyl methacrylate) (SBM) was investigated in three dimensions by transmission electron microtomography. Neat SBM self-assembled into a double-helical structure of polybutadiene (PB) domains around hexagonally packed core polystyrene (PS) cylinders in a poly­(methyl methacrylate) matrix. When PS homopolymer with a lower molecular weight than that of the PS block in SBM was added to the SBM, the PB domains transformed from double-helical structures to spherical domains, while maintaining the helical trajectories. In contrast, adding a higher molecular weight PS to the SBM changed the helical structures from double- to triple-stranded structures and even to four-stranded structures. The helical structures of the PB domains were strongly affected by the distribution of the blended polystyrenes in the core cylindrical PS domains