Jun-ichi Oku

Piezoelectric activity in films of poly(1-bicyclobutanecarbonitrile)

We observed significant piezoelectric activity in cast films of poly(1-bicyclobutanecarbonitrile).

Asymmetric cyanohydrin synthesis catalysed by a synthetic cyclic dipeptide

Asymmetric addition of hydrogen cyanide to benzaldehyde catalysed by cyclo(L-phenylalanyl-L-histidine) gave the highest optical yield ever obtained.

Synthesis of a poly(vinylidene fluoride) macromonomer

SummaryMethacrylate-type poly(vinylidene fluoride) macromonomer was synthesized from vinylidene fluoride via hydroxy-ended poly(vinylidene fluoride). The macromonomer copolymerized easily with methyl methacrylate, but homopolymerization did not proceed completely.

ph-Induced Conformational Change in An A- Helical Coiled-Coil is Controlled by His Residues in the Hydrophobic Core

An alpha-helical coiled-coil structure is one of the basic structural units in proteins. Hydrophilic residues at the hydrophobic positions in the coiled-coil structure play important roles in structures and functions of natural proteins. We reported here a peptide that formed a triple stranded alpha-helical coiled-coil showing the pH-dependent structural change. The peptide was designed to have two His residues at the hydrophobic positions of the center of the coiled-coil structure. The peptide folded into a triple stranded coiled-coil at neutral pH, while it unfolded at acidic pH. This construct is useful to create a protein that the structure or function is controlled by pH.

Condensation of Triethoxysilyl-Terminated Polystyrene with Acid Catalysts.

トリエトキシシリル末端ポリスチレン (TESi-PS) の縮合反応をいろいろなアルカリ触媒を用いて行った. 縮合反応は, アミンのような弱アルカリを触媒とした場合にはほとんど起こらず, 水酸化アルカリなどの強アルカリの場合に進行した. 強アルカリによる縮合反応の時間一縮合物生成率曲線には極大値が存在し, 長時間の反応で縮合物の生成率はゼロとなった. 例えば, NaOH触媒では縮合物の生成率は, 60℃4時間の反応で62%に達するが, 24時間以内には見かけ上ゼロとなった. これは, いったん生成した縮合物からポリスチレン部が脱離する反応が副反応として起こるためであることがわかった. 縮合反応と脱離反応において, 反応速度は前者の方が大きく, 活性化エネルギーは後者の方が大きい値を示した. この縮合反応で得られる縮合生成物はLiOH触媒ではTEsi-PSの4量体, NaOHとKOHでは5量体相当のものであり, 単分散性に優れた (Mw/Mn<1.1) ものであった.

Concentration-resolved 2D correlation gel permeation chromatography study of aggregate-aggregate interactions in the polymerization products of triethoxysilyl-terminated polystyrene silane-coupling agent.

Concentration-resolved 2D correlation gel permeation chromatography (GPC) has been used to examine the intricate details of the HCl-catalyzed polymerization of a polymeric silane-coupling agent (SCA), triethoxysilyl-terminated polystyrene (TESiPS). The concentration-resolved 2D correlation GPC maps directly reflect the marked difference in the aggregate-aggregate interactions of dilute and concentrated monomeric units, which govern the differences in the polymerized products. There is an optimum concentration of SCA for the enhancement of interfacial strength and subsequent polymerization. Thus, the concentration-resolved 2D correlation GPC technique can be used as a powerful tool for elucidation of aggregate-aggregate interactions and reaction mechanisms in a surface- or interface-enhanced reaction system. It has been shown that the yield value of polymerization products can be improved to a marked extent by choosing a high initial monomer concentration, due to the increase in the production of oligomers. Multiple reaction processes are promoted by the self-assembly of the monomeric and oligomeric components.

Anionic polymerization of vinylsilanes

SummaryThe anionic polymerization of dimethylphenylvinylsilane with sec-butyllithium/N,N,N′,N′-tetramethylethylenediamine (TMEDA) was investigated. The polymerization proceeded up to 100% yield and afforded the polymer having isomerized-structure units. The polymerization was accompanied by chain transfer reaction to the monomer and the polymerization rate in the presence of TMEDA was much lower than in the absence of TMEDA.