Original Article in 2016

This is the first report on exopeptidase-catalyzed oligopeptide synthesis. Oligo(l-leucine) was synthesized using the exopeptidase carboxypeptidase Y while preventing enzymatic hydrolysis. A high yield of the polypeptide with a narrow polydispersity was successfully obtained by limiting polypeptide cleavage during aminolysis.

We have demonstrated nano-wood materials derived from wood are useful as reducing and supporting agents in the one-step preparation of monodisperse Au NPs. The average diameter of the Au NPs could be controlled by varying the concentration of the Au precursor, and the size distribution could be improved by the addition of NaOH. The obtained monodisperse Au NPs/wood composites exhibit high catalytic activities in the reduction of p-nitrophenol as a model reaction.

The local and global conformations of flower micelles and flower necklaces formed by the amphiphilic alternating copolymer of sodium maleate and dodecyl vinyl ether P(MAL/C12) in an aqueous solution were investigated using small-angle X-ray scattering and light scattering. Both local and global conformations for micelles of P(MAL/C12) with N₀₁ (the degree of polymerization) < 300 and N₀₁ >300 have been explained consistently by the flower micelle and flower necklace models with minimum-sized loops, respectively, as previously proposed.

Radical polymerization of a bisacrylate monomer trans-1,2-bisacryloyloxyethylcarbamoyloxycyclohexane proceeded via cyclopolymerization. The repeating unit consisted of a 19-membered ring structure. Notably, highly selective cyclopolymerization proceeded at a monomer concentration of 0.033 mol l⁻¹ and produced the corresponding polymer in high yield. The selectivity was validated by size-exclusion chromatography, and nuclear magnetic resonance and matrix-assisted laser desorption ionization time-of-flight mass spectroscopic analyses.

The assembly structure and the critical rod length for the disorder–order orientational transition in rod–coil diblock copolymer films depend on the property of the wall surface and the film thickness.

The liquid crystalline (LC) behavior of two lyotropic systems, poly(p-phenylene terephthalamide) solutions in sulfuric acid and hydroxypropyl cellulose (HPC) solutions in water, was compared on a dynamic rheological basis. Two systems showed similar behaviors in molecular stress relaxation but different orientation relaxation time behaviors. The helicoidal structure of the HPC systems is transformed to a nematic-like directional order via the damping process under very high shear.

To control contamination resistance of polymer surfaces, the surface hydrophobization and hydrophilization were attempted by atmospheric pressure plasma jet (APPJ)-coating with hexamethyldisiloxane (HMDSO) and APPJ-oxidation, respectively. The APPJ-coating remarkably prevented the deposition of the particulate contaminants in air. The granular morphology was observed on the film surfaces after the APPJ-coating, which resulted in superior contamination resistance via the decrease in the contact area with the contaminant. On the other hand, the APPJ-oxidation promoted the contamination removal in the aqueous detergent system.

The first-order perturbation calculation is carried out of the second virial coefficient A₂ of the phantom Gaussian and Kratky–Porod wormlike rings without inter- and intramolecular topological constraints with consideration of the ternary-cluster integral β₃ in addition to the binary-cluster integral β₂. From a comparison of the present theoretical result with experimental data, the residual contribution of β₃ to A₂ is shown to be negligibly small for ring atactic polystyrene in cyclohexane at Θ in the range of the molecular weight M from 1 × 10⁴ to 6 × 10⁵.

Cationic polymerization of p-methylstyrene (pMeSt) was examined using various metal chlorides as Lewis acid catalysts in dichloromethane. Polymerization using SnCl₄ and ZnCl₂ in conjunction with 2,6-di-tert-butylpyridine (DTBP) proceeded in a controlled manner in contrast to the reactions with metal trichlorides, including AlCl₃, FeCl₃ and GaCl₃. In addition, the combination of SnCl₄ and DTBP allowed the controlled polymerization of less reactive styrenes and the synthesis of star-shaped poly(pMeSt)s through the cross-linking reaction using an alkylstyrene-type divinyl compound.

The 1:1 mixtures of zinc diacrylate (ZDA) and zinc dialkanoate (ZDC_x) was found to start melting at lower temperature than the melting points of the original components and polymerization of acrylate portions progressed in the molten state at lower temperature than the polymerization temperature of ZDA, In this process, ion exchange between ZDA and ZDC_x was confirmed to accelerate the reaction.

The sandwich-like sulfonated polyimide/chitosan (SPI/CS) composite membranes were prepared and the SDs of the SPI were adjusted from 30 to 70%. Based on the proton/vanadium ion selectivity and chemical stability, the SPI40/CS and SPI50/CS membranes are selected as optimum candidates for all-vanadium redox flow battery (VRFB) applications. The 100-time cyclic charge–discharge testing (50 mA cm⁻²) results show that the SPI40/CS membrane possessed higher coulombic efficiency than Nafion 117. In addition, the SPI40/CS membrane exhibited more stable energy efficiency than pure SPI40 membrane.

The catalytic activities of basic and thermoresponsive microgel particles for the Knoevenagel condensation reaction in water at ambient temperature were evaluated. The catalytic activity of the basic gel particles depended on their base strength. The tertiary-aminated microgel particles had the higher activity than tertiary-aminated silica gel, bulk gel and trimethylamine. Because the base strength of the tertiary amines in the microgel particles decreased with increasing temperature, the catalysts and residual substrates were separated by dialysis with heating. The recovered microgel particle catalysts were recyclable for an additional Knoevenagel condensation.

Polyimide aerogel (PIA) was used to synthesize low-dielectric-constant polyimide composite films. Unlike silica aerogel composites, the polyimide aerogel composite films were synthesized solely based on polyimide. The films maintained the original thermal and chemical properties of polyimide contributing to their homogeneity. The presence of uniformly dispersed aerogel, the high-thermal decomposition and glass transition temperature of the PI–PIA sample films were confirmed by field emission scanning electron microscope, TGA and DSC analysis. The FE-SEM image of the PI–PIA film samples indicates that the PIA particles were well-dispersed in the film and retained their spherical shape.

Novel polymeric metal complex dyes with phenothiazine or carbazole derivative as donor and Zn(II) or Co(II) complexes as acceptors were synthesized for dye-sensitized solar cells. The dyes based on carbazole derivatives exhibited wider absorption spectra, and after replacement of the Co(II) coordinated ion with Zn(II), a bathochromic shift in the absorption spectrum was observed. The device sensitized by P3 exhibited the best photocurrent conversion efficiency (2.06%). Moreover, these dyes all exhibited excellent chemical and thermal stability.

Optically active polyurethane (OPU) derived from chiral tyrosine possesses a single-handed helical conformation and optical activity owing to the induced asymmetric force field in the chiral monomer. The regular secondary structure facilitates the formation of numerous interchain hydrogen bonds, which increases the crystallinity and thermal stability of OPU. The high-temperature infrared spectroscopy results indicate that the hydrogen bonding collapses before thermal decomposition. Both helical stereostructures and hydrogen bonding contribute to the decreasing of infrared emissivity for OPU.

Amorphous and flexible tri-branched poly(ricinoleic acid) was introduced to semi-crystalline and rigid trans-1,4-polyisoprene from Eucommia ulmoides Oliver to improve the processing ability.

The spatial distribution of bromine-labeled hydrophobic molecules—bromobenzene (BrBz) and 4-bromobenzylalcohol (BrBzOH)—incorporated in polymer micelles of poly(N,N-dimethylaminoethyl methacrylate)-block-poly(methyl methacrylate) (PDMAEMA-b-PMMA) was investigated using anomalous small-angle X-ray scattering (ASAXS) near the Br K-edge. ASAXS analyses revealed that BrBzOH was homogeneously dispersed in the hydrophobic PMMA core of the PDMAEMA-b-PMMA micelle, whereas BrBz was excluded from the vicinity of the core–shell interface of the PMMA core. The results indicate that the spatial distribution of hydrophobic molecules in polymer micelles strongly depend on the polarity of the encapsulated species.

Multivariate analysis of ¹³C nuclear magnetic resonance (NMR) spectra successfully evaluated chemical composition and degree of branching value of radically prepared branched copolymers without assigning individual signals, although signals became broadened with increase in branching unit.

Triptycene-based porous organic frameworks (POFs) with high BET (Brunauer–Emmett–Teller) surface and tailored micropore environments were prepared through a facile external knitting strategy. The functionalized POFs exhibited very high aliphatic amine vapor uptakes of up to 5 times of their own weight, and more than 30 times selectivity for aliphatic amines over n-hexane, and thus they open up new opportunities for environment-related applications.

Magnetic-field-induced alignment of low-molecular-weight syndiotactic polystyrene (sPS) has achieved. Isothermal crystallization from the melting state containing local ordered domains under the 2 or 10 T of the magnetic-field-induced alignment of sPS crystals. The crystalized sPS samples formed the β phase, and the b-axis was aligned parallel to the magnetic field. Low molecular weight of sPS and high magnetic field were effective for high alignment degree. A stepwise crystallization attained higher alignment of sPS compared with an isothermal crystallization.