Rikukawa Masahiro

Abstract: Ruthenium-catalyzed olefin metathesis reactions were conducted in water with thermoresponsiveblock copolymers forming micelles. The block copolymers were prepared by living radicalpolymerization and consisted of a thermo-responsive and hydrophilic segments. The formersegment included poly(N-isopropylacrylamide) or poly(N,N-diethylacrylamide), and the latterpoly(sodium 4-styrene sulfonate), poly(sodium 2-acrylamido-2-methylpropanesulfonate) orpoly(ethylene glycol). Homometathesis, cross-metathesis and ring-closing metathesis reactions proceededto afford the products in moderate to good yields. Extraction efficiency from the reactionmixture was also studied.

S-6X multi-block copolymers can be developed by direct one-pot copolymerization via Ni(0) coupling reaction, allowing high conductivity and strength on a wide-range of IECs.

Rechargeable magnesium (Mg) batteries are envisioned as next generation batteries. The development of solid polymer electrolytes with high ionic conductivity will contribute to realize not only high performance Mg batteries but also reliable and safe devices. In this study, diblock copolymers (PPEGMA(m)-b-SPBn) with oligoether (PEGMA) and zwitterionic (SPB) side-chains are synthesized in order to develop novel Mg-ion electrolytes. PPEGMA(m)-b-SPBn copolymers with various unit ratios are synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. PPEGMA(m)-b-SPBn exhibited two distinct glass transition temperatures. Phase-separated structures are observed by atomic force microscope (AFM) measurements. PPEGMA(m)-b-SPBn/Mg-salt composites exhibited a glass transition temperature due to the mixture formation of PEGMA and SPB blocks. When the unit numbers of m and n are 44 and 75, respectively, PPEGMA(m)-b-SPBn/Mg-salt ([EO]: [Mg] = 6: 1) exhibits the highest ionic conductivity of over 10(-4) S cm(-1) at 60 degrees C among 11 composites prepared in this study.

A few kinds of thermoresponsive diblock copolymers have been synthesized and utilized for palladium-catalyzed coupling reactions in water. Poly(N-isopropylacrylamide) (PNIPAAm) and poly(N,N-diethylacrylamide) (PDEAAm) are employed for thermoresponsive segments and poly(sodium 4-styrenesulfonate) (PSSNa) and poly(sodium 2-acrylamido-methylpropanesulfonate) (PAMPSNa) are employed for hydrophilic segments. Palladium-catalyzed Mizoroki–Heck reactions are performed in water and the efficiency of the extraction process is studied. More efficient extraction was observed for the PDEAAm copolymers when compared with the PNIPAAm copolymers and conventional surfactants. In the study of the Sonogashira coupling reactions in water, aggregative precipitation of the products was observed. Washing the precipitate with water gave the product with satisfactory purity with a good yield.

Cellulose is the main component of biomass and is the most abundant biopolymer on earth; it is a non-toxic, low-cost material that is biocompatible and biodegradable. Cellulose gels are receiving increasing attention as medical products, e.g., as wound dressings. However, the preparation of cellulose hydrogels employing unmodified cellulose is scarcely reported because of the cumbersome dissolution of cellulose. In previous studies, we developed the new promising cellulose solvent N-butyl-N-methylpyrrolidinium hydroxide in an aqueous solution, which can dissolve up to 20 wt% cellulose within a short time at room temperature. In this study, we employed this solvent system and investigated the gelation behavior of cellulose after crosslinker addition. The swelling behavior in water (swelling ratio, water uptake), the mechanical properties under compression, and the antibacterial activity against Escherichia coli and Bacillus subtilis were investigated. We have developed a simple and fast one-pot method for the preparation of cellulose gels, in which aqueous pyrrolidinium hydroxide solution was acting as the solvent and as an antibacterial reagent. The pyrrolidinium hydroxide content of the gels was controlled by adjustment of the water volume employed for swelling. Simple recovery of the solvent system was also possible, which makes this preparation method environmentally benign.

A 2D perovskite incorporating an amine moiety with a carboxy group exhibited orientation changes as the amount of DMSO additive varied. The degree of perpendicular orientation was increased by optimizing the amount of DMSO additive, while using the bar-coating method. Moreover, film thickness and the ratio of perpendicular orientation exhibited a positive correlation.

Solid polymer electrolytes mainly based on polyethers have been actively investigated for over 40 years to develop safe, light, and flexible rechargeable batteries. Here, we report novel supramolecular electrolytes (SMEs) composed of polyether derivatives and a two-dimensional boroxine skeleton synthesized by the dehydration condensation of 1,4-benzenediboronic acid in the presence of a polyether with amines on both chain ends. The formation of SMEs based on polyether derivatives and boroxine skeleton was confirmed by Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (PXRD), and thermogravimetric (TG) analysis. Linear sweep voltammetry (LSV) and cyclic voltammetry (CV) were performed to evaluate the electrochemical stability and lithium conductive properties of SMEs with given amounts of lithium bis(trifluoromethylsulfonyl)amide (LiTFSA). The ionic conductivity of SME/LiTFSA composites increased with increasing lithium-salt concentration and reached a maximum value at a higher concentration than those of simple polyether systems. The lithium-ion transference number (t(Li+)) of SME/LiTFSA was higher than those of polyether electrolytes. This tendency is unusual for a polyether matrix. SME/LiTFSA composite electrolytes exhibited a stable lithium plating/striping process even after 100 cycles. The current density increased with an increasing number of cycles. The combination of ion conductive polymers and a two-dimensional boroxine skeleton will be an interesting concept for developing solid electrolytes with good electrochemical properties.

Poly (ethylene oxide) (PEO) has been investigated as an ion-conductive matrix for several decades due to its excellent properties. However, further improvements are needed to enable a PEO-based ion-conductive matrix for practical applications. In order to develop novel solid polymer electrolytes based on zwitterions, we synthesized diblock copolymers (PPEGMA-b-SPBs) with oligoether and zwitterionic side-chains and evaluated their physico-chemical properties. PPEGMA-b-SPBs with various unit ratios were synthesized by RAFT polymerization. PPEGMA-b-SPBs with/without LiTFSA exhibited two distinct glass transition temperatures regardless of the unit ratio of PEGMA and SPB. AFM observations clearly revealed phase-separated structures. The ionic conductivity of PPEGMA-b-SPBs increased even at a high salt concentrations such as [EO]:[Li] = 6:1 and was over 10(-5) S cm(-1) at 25 degrees C. This tendency is unusual in a PEO matrix. The oxidation stability of PPEGMA-b-SPBs was about 5.0 V vs. Li/Li+, which is a higher value than that of PEO. The improvement of the electrochemical properties is attributed to the introduction of the SPB block into the block copolymers. PPEGMA-b-SPBs were evaluated as cathode-coating materials for Li batteries. The discharge capacity and coulombic efficiency of the cells employing the cathode (LiNi1/3Mn1/3Co1/3O2 (NMC)) coated with the block copolymers were much higher than those of the cell employing the pristine cathode at the 50th cycle in the cut-off voltage range of 3.0-4.6 V.

Calcium-phosphate cements (CPCs) have been used as bone filling materials in orthopaedic surgery. However, CPCs are set using an acid-base reaction, and then change into stable hydroxyapatite (HAp) in a living body. Therefore, we developed bioresorbable chelate-setting β-tricalcium phosphate (β-TCP) cements based on surface modifications of inositol phosphate (IP6). In order to improve the bioresorbability, we fabricated IP6/β-TCP cements hybridized with poly(lactic-co-glycolic acid) (PLGA) particles as a pore-forming agent. The compressive strengths of the cements with the amounts of 5 and 10 mass% PLGA particles were 23.2 and 22.8 MPa, respectively. There was no significant difference from cements without PLGA (23.4 MPa). The setting times of the cement specimens with PLGA particles (30 min) were a little longer than those without PLGA particles (26.3 min). The lack of cytotoxicity of the cement specimens was confirmed using osteoblast-like cells (MC3T3-E1). Cylindrical defects were made by drilling into the tibia of mini-pigs and injecting the prepared cement pastes into the defects. Twelve weeks after implantation the specimens were stained with toluidine blue and histologically evaluated. Histological evaluation of cement specimens with PLGA particles showed enhanced bioresorbability. Newly-formed bone was also observed inside cement specimens with PLGA particles. The IP6/β-TCP cement specimens with PLGA particles had excellent material properties, such as injectability, compressive strength, high porosity, no cytotoxicity in vitro, bioresorption and bone formation abilities in vivo. Organic-inorganic hybridized CPCs are expected to be valuable as novel biodegradable paste-like artificial bone fillers.

<p>Poly(<italic>p</italic>-phenylene)-based sulfonated polymers with well-controlled IECs were synthesized <italic>via</italic> a three-step procedure including preceding sulfonation of precursor monomers.</p>

Organic ionic plastic crystals (OIPCs) have been studied as solid-state electrolytes owing to their desirable properties such as plasticity, non-flammability, and high ionic conductivity. However, the relationship between the ion structures and the properties of OIPCs are poorly understood. To supplement our previous work on the effects of the side chain structure of pyrrolidinium salts on their properties, this study examined the effects of the anion structure. For this purpose, five N,N-diethylpyrrolidinium ([C(2)epyr]) salts with various sulfonylamide anions were synthesized. The [C(2)epyr] salts with bis(fluorosulfonyl)amide ([FSA]) and bis(pentafluoroethanesulfonyl)amide ([BETA]) exhibited higher ionic conductivity values at room temperature than the other [C(2)epyr] salts. The H-1 and F-19 solid-state NMR results indicated that the component ions in [C(2)epyr][FSA] and [C(2)epyr][BETA] exhibited high rotational mobility, even in the solid state. Thus, rotational mobility is likely important for achieving high ionic conductivity.

Cellulose processing remains a challenge as it is insoluble in water and common organic solvents. Ionic liquids (ILs) are organic salts with a melting point below 100 degrees C and are known for their excellent solvent properties. Unlike common organic solvents, which can form toxic or flammable vapours due to their high volatility, ILs can be considered as more environmentally friendly due to their negligible vapour pressure and flame retardant properties. We found that N-butyl-N-methylpyrrolidinium hydroxide enables rapid dissolution of up to 20 wt% Avicel (R) cellulose at 25 degrees C in aqueous solution (50 wt% water), making it the first pyrrolidinium-based salt capable of dissolving cellulose. Furthermore, solubility studies are currently carried out mainly with the naked eye, microscopy or spectroscopy. The former is a subjective method because it depends on the observer, and particles at the micro-level cannot be seen with the human eye. Microscopic and spectroscopic analyses are suitable for the verification of solubility; however, the acquisition costs of the instruments are high, and sample preparation is time-consuming. We propose that turbidity is a suitable measure for solubility, and investigated a simple and fast method to evaluate cellulose solubility in aqueous N-butyl-N-methylpyrrolidinium hydroxide by employing a turbidimeter which was compared with microscopy and ocular (eye) observation. In this study, we have not only found a promising new solvent for cellulose processing, but also offer a reliable solubility analysis.

Organic-inorganic perovskites are composed of organic cations and [PbX6](4-) octahedra, and the properties change depending on the type of organic cations. To identify the effect of organic cations and control the properties of the perovskite, thin films were prepared using quaternary alkylammonium and quaternary alkylphosphonium cations, which have big steric effects. A big steric effect can generate the distortion of [PbX6](4-) octahedra leading to changes in properties. A thin film of a Pb-based organic-inorganic perovskite having quaternary alkylphosphonium cations was prepared for the first time. An exciton absorption was observed at a lower wavelength than other perovskites prepared from primary and quaternary ammonium salts. The perovskite with phosphonium groups was thermally stable compared with ammonium groups.

A two-dimensional perovskite incorporating an amine moiety with a carboxyl group exhibited variations in orientation with changes in the ambient humidity. It was possible to increase the degree of vertical orientation by optimizing the film thickness and promoting crystallization at the interface between the film and the film-forming atmosphere.

Palladium-catalyzed Mizoroki-Heck reactions were carried out in water using thermoresponsive polymer micelles. The micelles were generated from thermoresponsive block copolymers consisting of a poly(N-isopropylacrylamide) (PNIPAAm) segment and a hydrophilic segment such as nonionic poly(ethylene glycol) (PEG) (2) and anionic poly(sodium p-styrenesulfonate) (PSSNa) (9). These copolymers exhibited lower critical solution temperature (LCST) behavior at ca. 40-50 deg and showed thermal stimuli-induced formation and dissociation of micelles. The copolymers formed micelles in aqueous solution at higher temperature, where catalytic reactions proceeded. At lower temperature, the micelles dissociated to form a clear solution, enabling efficient extraction of the products from aqueous reaction mixture. In the presence of these copolymers, palladium complexes catalyzed the coupling reactions between aryl iodides and alkene compounds inside the hydrophobic micelle cores in water under relatively milder conditions. Extraction of the products from the aqueous solution of 2 or 9 was found to be efficient enough in comparison with conventional surfactants.

Ionic liquids (Ls) are promising electrolyte materials for developing next-generation rechargeable batteries. In order to improve their properties, several kinds of additives have been investigated. In this study, beta-cyclodextrin (beta-CD) was chosen as a new additive in IL electrolytes because it can form an inclusion complex with bis(trifluoromethylsulfonyl)amide (TFSA) anions. We prepared the composites by mixing N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfony)amide/LiTFSA and a given amount of triacetyl-beta-cyclodextrin (Ac beta-CD). The thermal behaviors and electrochemical properties of the composites were analyzed by several techniques. In addition, pulse field gradient NMR measurements were conducted to determine the self- diffusion coefficients of the component ions. The addition of Ac beta-CD to the IL electrolytes results in the decrease in the conductivity value and the increase in the viscosity value. In contrast, the addition of Ac beta-CD to the IL electrolytes induced an improvement in the anodic stability because of the formation of an inclusion complex between the Ac beta-CD and TFSA anions. CDs are potential candidates as additives in IL electrolytes for electrochemical applications.

Five kinds of protic ionic liquids (PILs) were synthesized by the neutralization reaction of amidine and carboxylic acid (acetic acid, propionic acid, or butyric acid), and the esterification reaction of cellulose, using acetic anhydride, was carried out in PILs. The obtained cellulose derivatives were soluble in DMSO. In the H-1 NMR spectra of the cellulose derivatives, not only the chemical shift of acetyl group derived from acetic anhydride, but also the chemical shift, based on the anion of PILs, were observed. The degree of substitution (DS) of the produced cellulose derivatives varied depending on the structure of PILs. The obtained cellulose derivatives showed a thermal decomposition temperature above 270 degrees C and a glass transition temperature below 170 degrees C.

This study demonstrates the supramolecular chirality control of a conjugated polymer via solvent polarity. We designed and synthesized a chiral polyfluorene-thiophene copolymer having two different chiral side chains at the 9-position of the fluorene unit. Chiral cyclic and alkyl ethers with different polarities were selected as the chiral side chains. The sign of the circular dichroism spectra in the visible wavelength region was affected by the solvent system, resulting from the change of supramolecular structure. The estimation of the solubility parameter revealed that the solubility difference of the side chains contributed to the change of the circular dichroism sign, which was also observed in spin-coated films prepared from good solvents having different polarities.

Cellulose acetate (CA) is a resin derived from biomass. In addition to its various superior properties, CA is preferable to existing petroleum-derived resins from the viewpoint of green chemistry. Therefore, the acetylation of cellulose is one of the most important subjects in cellulose research. In this study, we found that the acetylation of cellulose could proceed in some protic ionic liquids (PILs) composed of amidine and acetic acid with ΔpKa = ca. 8.4-8.7 under mild conditions without any catalyst. The degree of substitution (DS) of the produced CA was above 1.84, and the maximum DS was 2.87 when the ΔpKa of the PIL was about 8.5. In propionate-based PILs, cellulose was not only acetylated but also propionated however, the cellulose acetylation did not occur in formate-based PILs. It was revealed that the esterification of cellulose proceeded through the anion exchange between carboxylic anhydride and anion species of the PIL.

The conversion of cellulose into valuable chemicals has attracted much attention, due to the concern about depletion of fossil fuels. The hydrolysis of cellulose is a key step in this conversion, for which Brønsted acidic ionic liquids (BAILs) have been considered promising acid catalysts. In this study, using BAILs with various structures, their acidic catalytic activity for cellulose hydrolysis assisted by microwave irradiation was assessed using the Hammett acidity function (H0) and theoretical calculations. The glucose yields exceeded 10% when the H0 values of the BAIL aqueous solutions were below 1.5. The highest glucose yield was about 36% in 1-(1-octyl-3-imidazolio)propane-3-sulfonate (Oimps)/sulfuric acid (H2SO4) aqueous solution. A long alkyl side chain on the imidazolium cation, which increased the hydrophobicity of the BAILs, enhanced the glucose yield.

Colorless and transparent polybetainetype ion gels (PEG100CL2BTx (x = 0, 1, 3, 5, and 10)(the numbers indicate mole percent)) composed of poly(ethylene glycol) methyl ether methacrylate (PEGMA), [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide (BT) as the polymer matrix, N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)amide/lithium bis(trifluoromethylsulfonyl)amide (IL/Li) as the electrolyte, and a cross-linker (CL) were synthesized by in situ polymerization. These ion gels exhibited a glass transition temperature (Tg) at approximately -70°C, and their ionic conductivity was almost the same regardless of the x value. On the other hand, the oxidation stability of ion gels increased with increasing BT content. All ion gels exhibited a reduction peak for Li+ and an oxidation peak for Li. The current density and coulombic efficiency of PEG100CL2BT5 were higher than those of PEG100CL2BT0.

Polyphenylene-based hydrophilic-hydrophobic diblock copolymers were developed and used as ionomers in the catalyst layers (CLs) of polymer electrolyte membrane fuel cells. The introduction of aliphatic side chains into the polymer backbone provided high oxygen transport properties in the CLs and high overall performance of the fuel cells.

Two-dimensional perovskite compounds, (RNH3)2PbX4, have attracted much attention as quantum confinement materials. To achieve suitable orientation and exciton properties for optical applications, carboxy groups were introduced into the ammonium cations of two-dimensional perovskite compounds, which formed dimer structures based on the hydrogen bonding by the carboxy moieties. This structural organization allowed control of the layer orientation for favorable solar cells and thermal stability of the perovskites, while maintaining quantum confinement effects.

Formamidine (FA) and cesium (Cs) cations were introduced into quasi-two-dimensional (2D) perovskites as B site cations. The unique crystalline growth of the resulting (n-C6H13NH3)(2)FAPb(2)I(7), which promotes charge transport in photovoltaic solar cells, was confirmed, as was the stability of this material. The photovoltaic properties of (n-C6H13NH3)(2)FAPb(2)I(7) were found to be superior to those of other homologous quasi-2D perovskite compounds.

Geranial [(E)-3,7-dimethyl-2,6-octadienal], neral [(Z)-3,7-dimethyl-2,6-octadienal] and geraniol [(E)-3,7-dimethyl-2,6-octadien-1-ol] are found in lemon grass and are attractive essential oils with potential medicinal applications. In this study, a new method for extracting these natural flavour substances from lemon grass using co-solvent systems consisting of methanol or ethyl acetate and the ionic liquids 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) or 1-ethyl-3-methylimidazolium methylphosphonate ([C2mim][(MeO)(H)PO2]) is described.

Lemon myrtle is the richest natural source of citral, which has potential medicinal applications. In this study, citral was extracted from lemon myrtle using cellulose-dissolving ionic liquids (ILs), 1-ethyl-3-methylimidazolium methylphosphonate ([C(2)mim][(MeO)(H)PO2]), N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium chloride ([DEME]Cl), and N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium 2-methoxyacetate ([DEME][MOAc]). The extraction yield of citral obtained using ILs was up to 2.1 times higher than that obtained using ethanol. The ILs could be recycled and reused nine times for the extraction of citral. The present method provides a greener process when compared with conventional approaches and may be applicable for the extraction of other natural products.

The aldol reaction of 4-nitrobenzylaldehyde and cyclohexanone was catalyzed with the copolymer micelles, and the product was obtained in good yield with excellent diastereo- and enantioselectivity. Both the yield and stereoselectivity were superior to those obtained by using our previously developed proline-immobilized “broom”-type PNIPAAm-b- PEG copolymer catalysts. The Michael reaction was also catalyzed by the “linear”-type PNIPAAm-b-PEG catalyst and resulted in moderate yields with good stereoselectivity.