Kenjiro Onimura

Asymmetric anionic polymerization of maleimides bearing bulky substituents

Asymmetric anionic homopolymerizations of N-substituted maleimide (RMI) bearing bulky substituents [R = benzyl, diphenylmethyl (DPhMI), 9-fluorenyl (9-FlMI), triphenylmethyl, (diphenylmethyloxycarbonyl)methyl, (9-fluorenyloxycarbonyl)methyl] were carried out with complexes of organometal compounds (alkyllithium, diethylzinc) with six chiral ligands to obtain optically active polymers. The chiroptical properties of the polymers were affected strongly by the substituents on nitrogen in the maleimide ring, the organometal and chiral ligands. Poly(DPhMI) initiated by an n-butyllithium/(−)-sparteine (Sp) complex showed a positive specific rotation ([α] +60.3°). Poly(9-FlMI) prepared with a florenyllithium/Sp complex exhibited the highest specific rotation (+65.7°). The specific rotations of the poly(RMI) obtained were attributed to different contents between the stereogenic centers (S,S) and (R,R) based on threo-diisotactic structures of the main chain.

Asymmetric polymerization of N-substituted maleimides with chiral oxazolidine-organolithium

Asymmetric anionic homopolymerizations of achiral N-substituted maleimides (RMI) were performed with lithium 4-alkyl-2,2-dialkyloxazolidinylamide. All obtained polymers were optically active, exhibiting opposite optical rotation to that of a corresponding oxazolidinyl group at the terminal of the main chain. This suggests that opposite optical rotation to the corresponding chiral oxazolidine was induced to the polymer main chain. In the polymerization using a fluorenyllithium (FlLi)–oxazolidine complex, the obtained polymer with a fluorenyl group at the polymer end showed a negative specific rotation. This also suggests that asymmetric induction took place in the polymer main chain. The asymmetric induction was supported by the circular dichroism (CD) and GPC analysis with polarimetric detector. Optical activity of the polymer was attributed to different contents of (S,S) and (R,R) structures formed from threo-diisotactic additions, as supported by the 13C-NMR spectra of the polymers and the model compounds.

Synthesis and polymerization of Chiral methacrylates bearing a cholesteryl or menthyl group

Chiral methacrylates, that is, cholesteryl (ChMOC) and l-menthyl (MnMOC) N-(2-methacryloyloxyethyl)carbamates, were synthesized from 2-methacryloyloxyethyl isocyanate and cholesterol and l-menthol, respectively. Radical polymerizations of ChMOC and MnMOC gave number-average molecular weights for poly(ChMOC) and poly(MnMOC) of up to 3.74 × 104 and 9.39 × 104, respectively, and the specific rotations ([α]) were −43.1° to −47.7° and −87.6° to −89.0°, respectively. Temperature dependence of the specific optical rotation was observed for poly(ChMOC) but not for poly(MnMOC). The hydrogen bonds based on urethane segments for poly(ChMOC) were stronger than those for poly(MnMOC) according to IR spectra. In addition, the chiroptical properties of poly(ChMOC) were slightly affected by temperature in the presence of trifluoroacetic acid acting as an inhibitor for the formation of hydrogen bonds. Therefore, poly(ChMOC) may have a regular conformation due to hydrogen bonds and interaction between cholesteryl groups. Radical copolymerizations of ChMOC with styrene, methyl methacrylate, N-cyclohexylmaleimide, and N-phenylmaleimide were performed with 2,2′-azobisisobutyronitrile in tetrahydrofuran at 60 °C. Monomer reactivity ratios and Alfrey–Price Q–e were determined. Chiroptical properties of the copolymers were influenced by co-units. Thermal and X-ray diffraction analyses were performed for the homopolymers and copolymers.

Conductivity enhancement of polyacrylonitrile-based electrolytes by addition of cascade nitrile compounds

Abstract A cascade nitrile compound ([CH2N(CH2CH2CN)2]2, ED4CN) made by addition of acrylonitrile to alkyldiamine (1,2-diaminoethane), has been used as a plasticizer for solid polymer electrolytes. The ionic conductivity of a polymer electrolyte using this type of plasticizer in polyethylene oxide (PEO)– and polyacrylonitrile (PAN)–LiClO4 complex was measured. Addition of ED4CN to PEO-based electrolytes did not enhance the conductivity of them. However, interaction between ED4CN and lithium ions in the complex was confirmed by infrared spectroscopy. The peak assigned to the stretching vibration of nitrile group in ED4CN shifted to high-energy side. The shift indicated that the nitrile groups interacted with the lithium ions in the PEO-based electrolytes. Conductivity enhancement was observed in the PAN-based electrolytes containing ED4CN. Conductivity of the electrolyte containing ED4CN was about 10 or 23 times larger than that of the electrolyte without ED4CN. Addition of ED4CN to a PAN–LiClO4 electrolyte decreases the glass transition temperature of the complexes. Conductivity enhancement of the PAN-based electrolyte with ED4CN containing lithium salt in high concentration was also confirmed. Other low molecular weight additives, tetraethylsulfamide (TESA) and a cascade nitrile compound, ([CH2CH2N(CH2CH2CN)2]2, TE4CN) were also used and their possibility for a conducting enhancer of PAN-based electrolytes was tested. TESA was effective; however, TE4CN was inactive for a conductance enhancer of the PAN-based electrolytes.

Electrochemical behavior of polyaniline composite doped with poly [p-styrenesulfonate-co-methoxyoligo (ethyleneglycol) acrylate] in aqueous electrolyte and its application to the lithium ion concentration battery

Abstract Polyaniline-poly[ p -styrenesulfonate- co -methoxyoligo(ethyleneglycol)acrylate] composite, PANI-P(SS- co -MOEGA), was prepared from chemically synthesized PANI and P(SS- co -MOEGA). PANI-P(SS- co -MOEGA) composite film was cast onto an indium-tin oxide (ITO)-coated glass plate and electrochemical behavior of the modified electrode in 0.1 mol dm −3 LiClO 4 /0.1 mol dm −3 HClO 4 aqueous solution was investigated. XPS measurement of the composite film treated with potential cycling in the electrolyte solution indicated that cations (lithium ions) were doped from the electrolyte solution to PANI-P(SS- co -MOEGA) composite and dedoped from the composite film to the solution. The composite film is a pseudo n-dopable conducting polymer composite. A lithium ion concentration battery was constructed with PANI-P(SS- co -MOEGA) composite electrodes (anode and cathode) in 0.1 mol dm −3 LiClO 4 /0.1 mol dm −3 HClO 4 aqueous solution. The cell showed good cyclability (over 100 cycles) and high coulomb efficiency (about 100%).

Theoretical study on the polymerization mechanism of substituted maleimides by using a chiral catalyst with Zn2

Abstract It is possible to synthesize poly(N-substituted maleimide) by using a chiral complex consisting of a zinc and N -diphenylmethyl-1-benzyl-2-pyrrolidinoethanamine (DPhBP). The optical specific rotations [ α ] 435 25 in obtained polymers depend on the chirality of ligands in the catalysts. In the present study, density functional theory (DFT) calculations were adopted to investigate the polymerization mechanism in detail. The bulky diphenylmethyl group in the chiral ligand is effective to enhance the formation of the product in the initiation reaction. The geometry related to the pyrrolidine ring of the chiral ligand in the Zn catalyst is responsible for determining the configuration of polymers. It was also confirmed that the bulky substituent on the N atom of the N-substituted maleimide is another factor for obtaining polymers with high [ α ] 435 25 .

Synthesis of novel chiral poly(methacrylate)s bearing urethane and cinchona alkaloid moieties in side chain and their chiral recognition abilities

Abstract Two types of new chiral methacrylates, cinchoninyl(2-methacryloyloxyethyl)carbamate (CIMOC) and cinchonidinyl(2-methacryloyloxy-ethyl)carbamate (CDMOC) were synthesized from 2-methacryloyloxyethyl isocyanate (MOI) and cinchona alkaloid such as cinchonine and cinchonidine, respectively. Radical polymerizations of CIMOC and CDMOC were performed under several conditions to obtain the corresponding polymers whose specific optical rotations ([ α ] 435 25 ) were 84.0–89.0° and 0.39–0.72°, respectively. From the results of radical copolymerizations of RMOC (CIMOC and CDMOC, M 1 ) with styrene (ST, M 2 ) or methyl methacrylate (MMA, M 2 ), monomer reactivity ratios ( r 1 , r 2 ) and Alfrey–Price Q – e were determined: r 1 =0.18, r 2 =0.48, Q 1 =0.53, e 1 =0.92 for the CIMOC–ST system; r 1 =0.53, r 2 =0.26, Q 1 =4.91, e 1 =1.80 for the CIMOC–MMA system r 1 =0.59, r 2 =0.47, Q 1 =0.86, e 1 =0.33 for the CDMOC–ST system; r 1 =0.28, r 2 =0.59, Q 1 =2.15, e 1 =1.74 for the CDMOC–MMA system. The chiroptical properties of the copolymers were strongly influenced by co -units. Poly(RMOC)-bonded-silica gel as chiral stationary phase (CSP) was prepared for high performance liquid chromatography (HPLC). The CSPs resolved some racemates such as mandelic acid and trans -2-dibenzyl-4,5-di( o -hydroxyphenyl)-1,3-dioxolane by HPLC. The chiral recognition ability of poly(RMOC) may be due to the interaction between some cinchona alkaloid units and the racemates and/or to secondary and higher-ordered structures of the polymer.

Preparation of new polymer electrolytes based on poly(acrylonitrile-co-vinylimidazoline) matrix and improvement of polarization behavior of lithium electrode in the electrolyte by using cascade nitrile compound

Abstract New polymer electrolytes based on poly(acrylonitrile- co -vinylimidazoline), P(AN-VI) were prepared and their chemical and physical properties were characterized by conductance, DSC, and solid state 7 Li- and 13 C NMR measurements. Conductivity for the P(AN-VI)-based electrolytes was about 10 −4 S cm −1 at 30 °C and 10 −3 S cm −1 at 60 °C. Addition of the cascade nitrile compound, ED4CN {–[–CH 2 N(CH 2 CH 2 CN) 2 ] 2 } which acts as a plasticizer for polyacrylonitrile-based electrolytes, to P(AN-VI)-based electrolytes reduced their conductivities. Polarization behavior of a lithium electrode in the P(AN-VI)-based electrolytes was improved by the addition of ED4CN. Exchange current density of the lithium electrode in the P(AN-VI)-based electrolyte with ED4CN was one order of magnitude higher than that in the ED4CN-free P(AN-VI) electrolyte. Addition of ED4CN to the P(AN-VI)-based electrolyte changed the environment of the lithium ions in the electrolyte. Dominant coordination of the ED4CN molecules to the lithium ions was confirmed by 7 Li NMR measurements and increased the effective concentration of the lithium ions in the electrolytes.

Preparation of photo-patterned polymer–hydroxyapatite composites

A polymer–hydroxyapatite (HAp) composite is useful as hard tissue engineering scaffold materials for bone and teeth, particularly. It is necessary to control the form of the composites precisely, because form of bone and teeth is unique and specific. We demonstrated that the shape of a base polymer film was controlled by a photo-pattering technique. Hybridization of the photo-patterned polymer film and HAp was performed by alternative soaking of the film into calcium chloride aqueous solution and phosphate buffer solution. Poly(vinyl alcohol) bearing trans-cinnamate moieties as chromophoric groups (P(VA-VCI)) was spin-coated on various substrates, glass, metals such as titanium, aluminum, stainless steel. The spin-coated film was covered with a patterned photo-mask, exposed by using UV lamp and finally developed by dipping into mixed organic solvent. The patterned P(VA-VCI) film was processed by the alternate soaking process for preparation of P(VA-VCI)–HAp composites. We confirmed that formation of HAp in the P(VA-VCI) film by infrared spectroscopy and X-ray diffraction technique. Microscopic observations of the photo-patterned P(VA-VCI)–HAp composites were also performed. The border line between the polymer–HAp composite film and the substrate is clearly observed even after the alternative soaking process. This method is a method for being very useful for producing the polymer–HAp composite with the form of thought way.

Conductivity enhancement of polyethylene oxide-based polymer electrolytes containing cascade nitriles

Abstract New polymer electrolyte films, polyethylene oxide (PEO)-LiClO 4 complex containing a cascade (branched) nitrile conductivity enhancer, C 6 H 5 CH 2 N(CH 2 CH 2 CN) 2 , 2CN, or C 6 H 5 CH 2 N[CH 2 CH 2 CH 2 N(CH 2 CH 2 CN) 2 ] 2 , 4CN, were prepared by casting acetonitrile solution containing PEO, LiClO 4 , and the enhancer, 2CN or 4CN. Conductivity increased from 4.94 × 10 −7 S cm −1 for (PEO) 20 (LiClO 4 ) at 30°C to 1.35 × 10 −5 S cm −1 with the addition of 2CN forming (PEO) 20 (LiClO 4 )(2CN) 2 , and to 4.69 × 10 −6 S cm −1 with the addition of 4CN forming (PEO) 20 (LiClO 4 )(4CN) 0.5 . Addition of the cascade nitriles, 2CN and 4CN, increased the conductivity of the PEO-LiClO 4 complex by dissolution of lithium salt with the terminal nitrile groups.