Research articles

Piperazine and its derivatives were incorporated into a thin film of poly(vinyl alcohol), and the CO₂ separation performance of the resulting amin-containing membranes was investigated. The gas transport properties were dependent on the chemical structure of the amines. In particular, 3-(1-piperazinyl)-1,2-propanediol (PzPD)-containing polymeric membranes gave excellent CO₂ separation properties over H₂ and CH₄ under humidity. CO₂ interacted with the secondary amino group on the Pz ring to form a carbamate, which was readily hydrolyzed to produce bicarbonate ions. CO₂ migrates through the membrane in the form of bicarbonate ions.

For the development of wearable and stretchable devices, stretchable and flexible semiconductive materials are desired. To understand the mechanical behavior of structural deformation of polythiophene with disiloxane groups, we performed in situ measurements under stretching using X-ray diffraction of synchrotron radiation and polarized infrared spectroscopy. The behaviors of amorphous region was oriented during the initial deformation, while the orientation of crystallites began after permanent set.

Bridged polysilsesquioxanes are promising materials for reverse osmosis membranes because they exhibit robust properties. To investigate the effects of the polarity and rigidity of organic components of the polymer on the water permeability of the membrane, two alkoxysilane monomers, 2,5-bis[2-(triethoxysilyl)vinyl]pyridine (BTES-VP) and 1,4-bis[2-(triethoxysilyl)vinyl]benzene (BTES-VB), were synthesized. Both membranes prepared from BTES-VP and BTES-VB rejected 95–97% of aqueous sodium chloride and displayed water permeances of 1.1 × 10⁻¹³ and 8.5 × 10⁻¹⁴ m³/(m²· Pa· s), respectively.

Direct Observation of Cyclic Poly(N-substituted maleimide)s with Broad Size Distributions Synthesized by Anionic Polymerization using an N-Heterocyclic Carbene and Successive Ring Closure Without High Dilutions.

The synthesis of a novel conjugated polymer containing fused pyridinium units in its main chain is reported. A precursor polymer possessing pyridine and tetrafluorophenylene moieties was reacted in the presence of Lewis acid additives to promote the intramolecular nucleophilic aromatic substitution (S_NAr) reaction. The polymer reaction with BE₃-OEt₂ gave a product polymer soluble in polar organic solvents, and the successful formation of fused pyridinium ring structures was spectroscopically confirmed. The electrochemical and optical properties of the synthesized polymers were also investigated.

The fluorescent carbon nanoparticles were grafted with the copolymers of N-isopropylacrylamide and spiropyran (f-CNP-g-poly(NIPAM-co-SP)), which have dual responses to light and temperature stimuli when they are in an aqueous solution. The blue-green and red fluorescence of the f-CNP-g-poly(NIPAM-co-SP) nanocomposites dissolved in water could be reversibly switched under UV and visible light stimuli. Meanwhile, when the temperature increased from room temperature (20 °C) to 38 °C, the blue-green fluorescence intensity decreased, the red fluorescence intensity increased, and the average hydrodynamic diameter of the f-CNP-g-poly(NIPAM-co-SP) nanocomposites increased due to aggregation.

The mechanism of the heat-induced gelation of ovalbumin (OVA) under acidic conditions and the effect of amphiphilic peptide additives on gelation were investigated using dynamic light scattering (DLS) and small-angle neutron scattering (SANS). The molecular morphology and structure probed by DLS and SANS suggest that the heat-induced gelation of OVA solution forms a phase-separated structure. Heating of the solution of OVA and the peptide resulted in effective distribution of the peptide in the matrix of the heat-induced OVA gels and endowed the gel with increased strength.

Single- and two-photon holographic recording was investigated in photopolymer material consisting of two types of monomers: acrylamide (BAP) and epoxy (BOPS). Thus a cationic ring-opening polymerization and free-radical polymerization of monomers were initiated simultaneously. The arylsulfonium salt—cationic derivative of thioxanthenonium (CDTX) was chosen as the photoinitiator. The refractive index change n₁ and maximum recording rate (dn₁/dt)_max of holographic gratings were found in two-photon photoinitiation modes depending on the concentration of BAP (the molar fraction of BAP) in photopolymer composition.

Molecular structure of silica surface modifiers greatly controls the performance of silica-filled styrene-butadiene rubber (SBR) through interfacial characteristics of the composites. Soft nature of low molecular-weight hydroxyl terminated polybutadiene (HTPB) and small number of its covalent bounds to the rubber matrix was compared with large number of rigid covalent bounds made between bis(3-triethoxysilylpropyl)tetrasulfide (TESPT) and rubber. Despite the better dispersion of silica modified with the former, the latter ensures higher transfer of stress to particles at large strains, inducing improved strength and abrasion resistance to composites.

We investigated the biosynthesis and properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) produced by Haloferax mediterranei from glucose. Size-exclusion chromatography revealed that PHBV produced by H. mediterranei in flask cultures had a weight-average molecular weight of 4.7 × 10⁶ g/mol, demonstrating production of ultrahigh-molecular-weight (UHMW) PHBV. The UHMW-PHBV (7 mol% 3-hydroxyvalerate, M_w = 4.4 × 10⁶ g/mol) obtained by jar fermenter cultivation was used to produce tenfold cold-drawn films with a tensile strength of 258.7 MPa. This suggests that UHMW-PHBV has a potential for practical, strong films.

A fluorescence film sensor film was prepared from 2,2,6,6-tetramethyl-1-piperidinyloxy radical-oxidized cellulose nanofiber, which was chemically immobilized by the Cu²⁺- or Cs⁺-selective ligand, 3,5-bis(((2-hydroxynaphthalen-1-yl)methylene)amino)benzoic acid. The potential of the current sensor is that it is a film-type sensor with facile removal from test water without leaving sensing residue in the water.

The investigation of the effects of incorporating various phenolic compounds on the curing of bisphenol A dicyanate (BADCY) revealed that o-(dimethylamino)methylphenol (o-DAMP) was a very effective catalyst, which reduced the final curing temperature to 180 °C. The promoting effect of o-DAMP was due to the presence of a phenolic OH and a (dimethylamino)methyl groups at the ortho-positions of the molecule. The addition of o-DAMP improved the mechanical properties of the cured BADCY resins, and the most balanced properties were obtained when the ratio of OH to OCN was 0.05.

When the neat PMMA samples were dried at room temperature, the glass transition temperature (T_g) increases linearly with the decrease in the amount of residual solvent. However, even if the residual solvent is extrapolated to 0 wt%, the T_g is significantly lower than the bulk T_g despite no residual solvent. The T_g of heat-dried samples heat treated at 120 °C also increases linearly with decreasing residual solvent content. However, T_g was significantly different depending on the drying temperature even with the same residual solvent amount. These results indicated that the PMMA samples dried at room temperature have a distinctly different molecular mobility from the heated sample.

The molecular dynamics of PCL-grafted polyrotaxanes (PRs) homogeneously dispersed in a cross-linked epoxy network were investigated using viscoelastic mechanical measurements and relaxation time measurements with pulsed NMR spectroscopy. With increasing temperature, the PEG axial chains in the PRs exhibit a glass-rubber transition and start fluctuating in the CDs with glassy PCL graft chains, which causes viscoelastic mechanical relaxation.

The mechanical properties of a unidirectional carbon fiber (CF)-reinforced polyamide 6 (PA6) composite subjected to a tension perpendicular to the CFs was studied by using two types of CFs with different surface profile. The difference of local crystalline structure of PA6 among CFs can be affected to the mechanical behavior of unidirectional PA6/CF composite under transverse tension.

In this study, a novel pyrazole–carbodithioate-based chain transfer agent (CTA) featuring an aldehyde group (CTA-CHO) was designed and synthesized. The newly synthesized CTA-CHO was used for the RAFT polymerization of styrene to afford well-defined polystyrenes end-functionalized with an aldehyde unit (PSt-end-CHO). The obtained PSt-end-CHOs feature low Ð values (~1.1), suggesting a living nature of the polymerization. Furthermore, the Passerini three-component reaction was successfully performed on the PSt-end-CHOs.

The thermoresponsiveness of hydrogel microspheres (microgels) was visualized in situ at the nanoscale using temperature-controllable high-speed atomic force microscopy (TC-HS-AFM). The morphological changes of the microgels are strongly affected by their packing conditions and by their adsorption on a solid substrate. The isolated microgels attached to the substrate show a simple increase in height and a constant width with decreasing temperature. On the other hand, both the width and the height of the densely packed microgels increase, and the structures of the microgels change from spherical to hexagonal during cooling.

A nitrile N-oxide-functionalized polypeptide was synthesized by a two-step method involving the combination of ring-opening polymerization of an amino acid N-carboxyanhydride (NCA) monomer using a primary amine initiator containing a nitroalkane group and a subsequent terminal conversion. The formed peptide was fully characterized by NMR, FT-IR, and MALDI-TOF MS measurements. The catalyst-free grafting reaction of the formed functionalized peptide with rubbers containing double bonds was achieved with high efficiency via an environmentally benign process. These results surely contributed to the development of novel peptide-grafted polymers.

This study predicted the absolute values of the heat capacities from the molecular formula per monomer for a main-chain-type polymer below the T_g. The calculations combined the Tarasov equation, the Einstein equation, and the (C_p − C_V) correction term, accounting for the degrees of freedom of the monomer unit. The difference of predicted and experimental heat capacities of poly(4-methyl-1-pentene) was within 8.0% from 90 to 180 K and within ±2.0% agreement from 180 to 300 K. For poly(vinyl benzoate), the values were within ±2.0% from 190 to 350 K, and for poly(1,4-butylene adipate), they were within ±2.0% from 80 to 200 K. The predicted heat capacity was accurate, especially in the high-temperature region above 180 K.

To better understand the heat capacities of polymer solids and considering that more than a dozen types of data on the absolute heat-capacity values of polymer compounds already exist, we evaluated the heat capacities of eight polyesters and five poly(oxide)s polymer solids with a carbon and oxygen backbone. Our calculations combined the Tarasov equation, the Einstein equation, and the (C_p − C_V) correction term, accounting for the degrees of freedom of the monomer units. Using the combined Tarasov and Einstein equations, the heat capacities of the analyzed polymer solids were reproduced by only three fitting parameters. The reproduced and experimental heat capacities of all samples except polycaprolactone and poly(3,3-bis(chloromethyl)oxetane) agreed within ±2.5%, and the errors for polycaprolactone and poly(3,3-bis(chloromethyl)oxetane) were within ±4.0%.