Shuhei Yamada

Concentration-driven phase control for low temperature synthesis of phase-pure anatase and rutile titanium oxide.

It is highly desirable to develop controlled synthetic methods at low temperature (<100 °C) for defined phases of titanium oxide nanoparticle. We present here a simple low temperature approach which is based on the peroxide route. This approach allows the preparation of phase-pure rutile and anatase without the use of any additives or surfactants or external acids. The formation of crystalline phases is found to be dependent on reaction temperature and highly dependent on concentration. Phase-pure rutile is obtained in two concentration zones while phase-pure anatase is obtained in one concentration zone. The relationship between phases and reaction conditions (concentration and temperature) fits well with the nucleation diffusion rate model.

Synthesis of block copolymers through umpolung or treatment of propagating end of living cationic polytetrahydrofuran

Block copolymers containing polytetrahydrofuran segments were synthesized by umpolung or propagating end of the cationic living polymer and successive anionic polymerization of methacrylates (RMAs) or radical polymerization of RMAs, acrylonitrile (AN), and styrene (St). Living polytetrahydrofuran (poly-THF) was prepared by cationic polymerization of tetrahydrofuran (THF), whose propagation end was reduced by samarium(II) iodide (SmI2). Anionic polymerizations of RMAs were conducted by addition of the monomers to the reduced poly-THF to obtain poly(THF-b-RMAs). On the other hand, the 2-bromoisobutyrate group, which can act as an initiator of radical polymerization, was introduced to the cationic propagating end of poly-THF by adding sodium 2-bromoisobutyrate. Block copolymers were synthesized by living radical polymerization of RMAs, St, or AN using the 2-bromoisobutyrate-capped poly-THF as a macroinitiator and copper(I) bromide (CuBr) as a catalyst.