Research articles

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  • The real-time structural changes of thermoresponsive polymer vesicles upon cooling were investigated by small-angle X-ray scattering and confocal laser scanning microscopy. The disassembly process of the vesicles consists of multiple steps: 1) pore formation, 2) opening and shrinkage of the membrane, and 3) dissolving in the solvent. We also demonstrated that the vesicles can be used as compartments for the controlled release of proteins. This study provides the basis for the mechanism of the disassembly process of thermoresponsive vesicles and a guideline for their use as controlled-release medical devices.

    • Tomoki Nishimura
    • Yoshihiro Sasaki
    • Kazunari Akiyoshi
    Original Article
  • The polymerization of divalent acyl-1,2,4-triazoles and diols/bisphenols afforded a series of aromatic, semiaromatic, and aliphatic polyesters. Compared with polymerization by transesterification, this polymerization proceeded irreversibly at relatively low temperature (<100 °C) without a metal catalyst. The reactivities of acyl-1,2,4-triazoles were thus comparable to acyl chlorides. On the other hand, higher crystallinity and lager masses of acyl-1,2,4-triazole caused technical problems, particularly for the synthesis of polyarylates. Nevertheless, solution polymerization was effective to prepare polyacrylates, particularly which could not be synthesized by interfacial polymerization.

    • Yasuhiro Kohsaka
    • Ichiro Mori
    • Yoshikazu Kimura
    Original Article
  • The microwave heating technique has been widely used in various organic and inorganic syntheses, and it has been reported that this technique provides the desired compounds quickly and easily. In this work, we applied microwave heating to synthesize redox-active organic nanoparticles consisting of hyperbranched viologen units. By the precise temperature control afforded by use of microwave irradiation, we succeeded in controlling the growth and termination reactions kinetically and preparing viologen nanoparticles in one-pot. We also demonstrated that the size of the nanoparticles can be controlled by varying the temperature program.

    • Kenya Komoda
    • Takehiro Kawauchi
    Rapid Communication
  • Amphiphilic diblock copolymers (M98En) composed of hydrophilic poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) and hydrophobic poly(2-methoxyethyl acrylate) were synthesized via controlled radical polymerization. M98En formed micelles in water, which can encapsulate hydrophobic guest molecules into the core. The micelles did not interact with proteins in an aqueous solution due to the PMPC shells.

    • Alisa Tsuji
    • Thi Lien Nguyen
    • Shin-ichi Yusa
    Original Article
  • Polymeric hydrogen carrier with high thermal stability was prepared by incorporating isopropanol and acetone units into polymers via a facile reaction process. Reversible hydrogen fixing and releasing were achieved with full conversion under mild conditions. Temperature-dependent facile hydrogenation and dehydrogenation cycle that operated at temperatures higher than the boiling points of isopropanol and acetone, in the presence of an iridium complex catalyst, was established by virtue of having these groups as pendants of the vinyl chain, with a compact repeating unit to maximize the mass hydrogen storage density of 2.8 wt%.

    • Kouki Oka
    • Yuka Tobita
    • Kenichi Oyaizu
    Original Article
  • In this Note, the heat-proofing and anti-plasticizing nature of poly(ethylene carbonate) by the addition of a defibered plant (DP) is presented. The DP was obtained via simple wet-milling treatment for water-dispersed Japanese cedar. The presented results encourage us to use plants as functional fillers without a special chemical/biological reaction.

    • Kazuhiro Shikinaka
    • Ai Tsukidate
    • Yuichiro Otsuka
  • The mechanical stretching behavior of poly(styrene-b-ethylene-co-butylene-b-styrene) (SEBS) was investigated under three different stretching modes and through in situ SAXS analysis. SEBS exhibited smaller hysteresis during cyclic equi-biaxial stretching than that of uniaxial stretching. SAXS measurement revealed that affine deformation occurred in the smaller stretching ratio (λ) region for both uniaxial and equi-biaxial stretching modes and deviation from affine deformation occurred for uniaxial stretching mode at the larger λ region. This is because entangled loops of poly(ethylene-co-butylene) chains serves as cross-linking points when films are stretched under equi-biaxial stretching mode.

    • Nattanee Dechnarong
    • Kazutaka Kamitani
    • Atsushi Takahara
    Original Article
  • Poly(trimethylene carbonate) (PTMC) based polymers were blended with N,N,N-trimethylchitosan (TM-CS). The tensile strength of the chitosan (CS) and TM-CS films blended with PTMC was found to cause brittleness, but a PTMC derivative copolymer bearing carboxylic acid improved the elongation properties of TM-CS. A softer film was obtained for a blend film composed of TM-CS with 25% consisting of an added PTMC derivative copolymer bearing a 10% carboxylic acid moiety on the side chain. This is the first report of the modification of CS using polymers with a PTMC backbone.

    • Koichi Irikura
    • Natjaya Ekapakul
    • Hiroharu Ajiro
    Original Article
  • A preparation of polyacrylate-based vitrimer-like elastomers with dynamic bond-exchangeable cross-links is demonstrated. The component polymer is a poly(ethyl acrylate)-based copolymer bearing pyridine groups randomly, which was cross-linked by a quaternization reaction of pyridine groups with dibromo cross-linkers (dibromo hexane). The bond exchange is induced via trans-N-alkylation of quaternized pyridines at high temperatures, which is revealed by temperature-ramp FT-IR, elongational creep, and stress-relaxation tests. Some useful functions of the present material, such as reprocessability, thermal and chemical recyclability, are provided due to the bond exchange nature.

    • Mikihiro Hayashi
    • Yuta Oba
    • Akinori Takasu
    Rapid Communication
  • We developed a W/O miniemulsion reactor system enabling the preparation of biopolymer nanoparticles and control of their morphologies and inner microstructures. We produced agarose hydrogel nanoparticles (AgarH) by the gelation of agarose in nanodroplets of a W/O miniemulsion. Next, we prepared agarose xerogel nanoparticles (AgarX) by precisely tuning the water evaporation from AgarH. We controlled the morphologies (solid and hollow) and crystal structure of AgarX by changing the pressure and temperature. The resultant AgarX possessed high crystallinity and thereby exhibited water resistance better than AgarH.

    • Yuuka Fukui
    • Ryutaro Inamura
    • Keiji Fujimoto
    Original Article
  • Free-standing, tartaric acid cross-linked chitosan thin films doped with magnetically aligned NiO-Co3O4 filler were successfully synthesized using facile solution-casting method under externally applied magnetic field. The aligned membranes displayed higher proton conductivity than Nafion-212 when measured by both two-probe and four-probe techniques in zero humid conditions. The membranes also showed excellent thermal, oxidation, and mechanical stability.

    • A. I. Anu Karthi Swaghatha
    • Louis Cindrella
    Original Article
  • A series of aliphatic polycarbonate-based polyurethanes with different content of cyclic structure was synthesized. There were more hydrogen bonds between soft and hard segments formed as the content of cyclic units increased. The mechanical and thermal properties of the environment-friendly polycarbonate-based polyurethanes can be enhanced and controlled by varying the content of the cycloaliphatic structures. These polyurethanes can be considered as high potential materials that can be used in different applications in the future.

    • Yuan-Hsiang Wu
    • Cheng-Chien Wang
    • Chuh-Yung Chen
    Original Article
  • Catalytic ester-interchange reactions allow new sequence information to be written statistically into poly(ester-imide) chains based on NDI (1,4,5,8-naphthalenetetracarboxylic diimide) units. Insertion of the cyclic ester cyclopentadecanolide (“exaltolide”) into an NDI-based homopolymer and quantitative sequence exchange between two different homopoly(ester-imide)s are both catalyzed by di-n-butyl tin(IV) oxide. Emerging sequences from these reactions are identified using pyrene-d10 as a “reader molecule” that binds rapidly and reversibly to the NDI residues, and amplifies the separation of 1H NMR resonances associated with different sequences via cumulative aromatic ring-current shielding.

    • Marcus Knappert
    • Howard M. Colquhoun
    Note Open Access
  • Our retinal prosthesis, referred to as a dye-coupled film, was developed by chemically coupling photoelectric dyes to the surface of a polyethylene film for restoring retinitis pigmentosa. However, the amount of coupled dye decreased during an implantation test in a monkey’s eye. For improving long-term durability, anion exchange from Br to PF6, BF4, and bis(trifluoromethanesulfonyl)imide (TFSI) was conducted. The long-term durabilities of the dye-coupled film–PF6, –TFSI, and –BF4 improved by 637, 215, and 48%, respectively, indicating that the dye-coupled film–PF6 exhibits the best long-term durability.

    • Koichiro Yamashita
    • Tenu Tanaka
    • Tetsuya Uchida
    Original Article
  • A reduction-responsive oligonucleotide was successfully constructed by post-modification of an oligonucleotide with a diazo compound bearing a 4-nitrobenzyl group as a reduction-responsive cleavable moiety. High-performance liquid chromatography and mass spectrometry were used to reveal the introduction of the 4-nitrobenzyl group to the 5′-phosphate group of the oligonucleotide, and the subsequent reduction-triggered recovery of the original oligonucleotide. The protocol used for the preparation of this reduction-responsive oligonucleotide is simple and it will have various applications in the fields of chemical and synthetic biology.

    • Nanami Shirakami
    • Sayuri L. Higashi
    • Masato Ikeda
    Rapid Communication Open Access
  • A microstructured film was fabricated using the breath figure method, and a slippery surface was achieved by infusing silicone oil onto the film. Among the obtained samples, oil-supported pincushion films (oPCF) most efficiently prevented water droplets and microorganisms from adhering to the surfaces. In addition, the adhesion of E. coli and B. subtilis to oPCF was reduced to 7.1 and 13% of that pertaining to PTFE, respectively. These results suggest that our efficient antifouling substrate can ensure human health and environmental safety without the use of any toxic compounds.

    • Ryunosuke Shimura
    • Hiroya Abe
    • Chihiro Inoue
    Original Article
  • Thermoresponsive degradable copolymers and hydrogels were synthesized by radical copolymerization of 2-methylene-1,3-dioxepane (MDO) and N,N-dimethylacrylamide (DMAAm). These prepared materials showed thermoresponsive property through the balance of hydrophobic MDO and hydrophilic DMAAm in the polymer chain. Under alkaline conditions (pH 11.3), these materials degraded and turned into water-soluble oligomers. In addition, the hydrogels self-degraded in PBS due to the decreased pH of the inner hydrogel. The prepared thermoresponsive degradable hydrogels are expected as stimuli-responsive drug delivery carriers and cell culture scaffolds.

    • Syuuhei Komatsu
    • Takuya Sato
    • Akihiko Kikuchi
    Original Article
  • Dissolved polymers directed molecular crystallization behavior under dilute and crowding conditions. Larger poly(ethylene glycol)s (PEGs) accelerated caffeine crystal formation in the dilute regime of PEG solutions, which was attributed to the depletion attraction that promoted caffeine cluster aggregation into crystal nuclei. In the semidilute regime, the crystal formation rate was insensitive to the molecular weight of PEGs. This observation was consistent with polymer blob properties, which govern depletion attraction and maintain a constant size at a given polymer concentration, irrespective of molecular weight in the semidilute regime.

    • Yuuki Hata
    • Xiang Li
    • Takamasa Sakai
    Original Article
  • The silicone rubber materials with foam/solid alternating multilayered structure have been constructed by combining two methods of the multilayered hot-pressing and supercritical carbon dioxide (SCCO2) foaming. The growth of the cell is restrained by the solid layer, resulting in a decrease of the cell size. In addition, the introduction of the solid layer can effectively improve the mechanical properties of the microcellular silicone rubber foam. The experimental results are analyzed by finite element analysis (FEA).

    • Wenhuan Zhang
    • Zhaoping Deng
    • Tao Liu
    Original Article Open Access
  • Thin film aromatic polyimides were quantitatively analyzed by grazing-incidence X-ray diffraction (GI-XRD), variable-temperature infrared p-polarized multiple-angle resolution spectroscopy (VT-pMAIRS), and spectroscopic ellipsometry (SE) methods. Combining VT-pMAIRS and GI-XRD revealed characteristic heterogeneous structures comprising non-oriented amorphous and oriented liquid-crystalline glass regions. Additionally, SE indicated that the film involved anisotropic-shaped void inducing form-birefringence. Such an excess of birefringence can make it difficult to estimate orientational order using birefringence measurement. This methodology presented here will remarkably contribute to general structural analyses of all intriguing thin-film polymers with characteristic heterogeneity.

    • Ryohei Ishige
    • Kazuyuki Tanaka
    • Shinji Ando
    Original Article