Research articles

Amphiphilic peptides bearing an alternating binary pattern of hydrophilic and hydrophobic repeating units were synthesized via polymerization exploiting Ugi’s four-component condensation reaction (Ugi’s 4CC) as the elemental polymerization reaction. We performed turbidity measurements on the aqueous polymer solutions at various temperatures. The results showed that the structural effects of the alternating peptides had the following impacts on thermoresponsiveness: (i) alternating peptides consisting of repeating hydrophilic and hydrophobic units tended to adopt upper critical solution temperature (UCST) behavior; and (ii) when the hydrophobes in the polymer were large enough for the intrachain hydrophobic interactions, the polymer displayed lower critical solution temperature (LCST) behavior. We also prepared thermoresponsive hydrogels comprising alternating peptide skeletons as the cross-linking points. Alternating peptides with LCST behavior may be useful for creating peptide-based smart materials in the future.

Spherical hydrogels (ENTG-co-PSβCyD) were prepared by photocopolymerization of the polyethylene glycol macromonomer ENTG and the polysubstituted photocross-linkable β-cyclodextrin (β-CyD) macromonomer PSβCyD. The optimum composition ratio for use of this hydrogel as a microbe-immobilized support was examined, along with the phenol (PhOH)-removing capability of PhOH-decomposing bacteria immobilized on this hydrogel. The best microbe-immobilized support had a PhOH-removal rate of 0.76 mg (L h hydrogel g)⁻¹. This removal rate was 1.7 times faster, and the amount of free bacteria in the assay medium was 3.6 times lower than the corresponding data obtained using a microbe-immobilized hydrogel without PSβCyD.

Amine-containing polysilsesquioxane (PSQ) membranes were studied with regard to their CO₂ separation ability. PSQ membranes were prepared by using amine-containing monomers, bis(triethoxysilylpropyl)amine (BTESPA), (aminopropyl)triethoxysilane (APTES), and (aminoethylaminopropyl)triethoxysilane (AEAPTES). The CO₂ permeances of the membranes prepared by 1:1 copolymerization with bis(triethoxysilyl)ethane increased in the order of AEAPTES-derived membranes < APTES-derived membranes < BTESPA-derived membranes, and their CO₂/N₂ permselectivities decreased in the same order. Copolymerization under acidic conditions resulted in the formation of ammonium-containing membranes with improved CO₂ permeances and acceptable CO₂/N₂ permselectivities.

Living radical polymerization was carried inside a liposome to prepare a deformable nanocapsule. The obtained nanocapsules showed good absorption of chemical substances depending on the binding ability to the incorporated polymers, and the absorption capacity could be controlled by the length and dissolved state of the polymer chains. Dynamic morphological changes in the capsules were observed when liposomes with high membrane fluidity were employed. Deformation of nanocapsules were induced by altering the pH value and ionic strength, resulting in the release of cargo in response to these environmental conditions.

Nanostructured polymer membranes were prepared from ionic liquid-crystalline (LC) monomers with taper-shaped mesogens. The virus removal properties of the ionic 1D channels prepared from a columnar (Col) LC phase were examined. In addition, as the first approach for LC membranes, the removal of several viruses from their cocktail solution by the 1D channels of Col membrane and 3D channels of bicontinuous cubic membrane was also studied.

A newly synthesized polyurethane (PU) was used to increase the flexibility of Bombyx mori silk fibroin (SF) fiber by making a composite of SF and PU, which is expected to increase applications of SF fiber in biomaterials. Namely, the elongation at break of the fiber increased by 1.3–1.8 times compared with that of regenerated SF fiber. The main reason for the increased flexibility of the SF-PU composite fiber is the increase in the fraction of random coils in SF, which was clearly observed by ¹³C solid-state NMR.

Perfect syndiospecific polymerization of triphenylamine-substituted styrene derivatives were achieved by using a rare-earth metal catalyst. The copolymerization of FSt with Styrene afforded copolymers have random or gradient sequence distributions and easily tunable incorporation rate.

Poly(3,4-ethylenedioxythiophene) doped with poly(4-styrene sulfonate) (PEDOT: PSS) films have strong potential for application in flexible transparent conductive electrodes. In this study, the electrical conductivity of PEDOT: PSS is shown to be enhanced by a bisphenol additive, bis (4-hydroxyphenyl) sulfone (BPS). The effects of BPS on the chemical structure of PEDOT: PSS were investigated using X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy. The PEDOT: PSS conformation is found to undergo a transformation into a highly conductive structure following the addition of BPS.

The PEDOT: PSS/PNIPAM hydrogel was simply prepared by ultrasound-enhanced free radical polymerization in an ice bath, in open air rather than spending hours under an N₂ purged environment. The resulting conductive hydrogel had a uniform texture and good flexibility for rapid resistance responses and color changes when it was exposed to temperature stimulations. The dual actions of hydrogen bonding and hydrophobic aggregation weaken the Coulomb interaction between PEDOT⁺ and PSS⁻ for better conductivity that is suitable for breathing monitoring and other wearable sensing applications.

Crystalline embryos initiated at early stage of the spinodal decomposition (SD) grew to anisotropically shaped crystallites and then the neighboring crystallites were collided by interpenetration of the lamellae within the continuous bisphenol-A polycarbonate (BPA-PC) rich phase at late stage of the SD. Such characteristic crystallization behavior is attributed to the constraint crystallization growth within the continuous BPA-PC rich region due to interconnected phase structure obtained by the liquid–liquid phase separation via SD.

Using LV-STEM, we found that there were previously unseen nanoscale structures inside the blends of PMMA/PVDF. These structures were formed on the same scale that did not deviate from the size of a single molecular chain, regardless of the solution casting, melt mixing, mixing ratios, and even amorphous or crystalline state of PVDF. The characteristics of these structures were discussed in accordance with thermophysical properties and intermolecular interaction properties, which provides some new findings for the first time.

In the polypropylene (PP)/carbon fiber (CF) composite, it has been well known that maleic acid modified PP (MAPP) improves the interfacial adhesion with CF. However, the effect of maleic acid modification on the PP crystals around CF, and that of the PP crystals on the interfacial adhesion have not been clarified well. In this study, the local crystal structure of PP near CF was investigated using micro-Raman spectroscopy, and it was demonstrated that the crystal growth of PP near CF contributes significantly to the interfacial adhesion.

All-cellulosic robust composite directly made from cellulose acetate (CA) and nanofibrillated bacterial cellulose (NFBC) sol was developed in this study. The key processes were utilizing a water/organic mixed solvent, for example, acetone, to maintain a good dispersion of the NFBC and good dissolution of CA, along with evaporating this mixed solvent without significant aggregation of the NFBC. Both CA and NFBC can be made from agricultural waste by combining chemical and biochemical processes. The CA/NFBC composite thus prepared is one of the promising green materials in the near future.

In this study, we examined the efficiency of q1-complex and L-SPG complex in translocation to the cytoplasm. The results showed that the q1 complex can deliver YB-1-AS into the cytoplasm about three times more efficiently than the L-SPG complex.

Multivariate analysis of ¹H NMR spectra of copolymers of methyl methacrylate and benzyl methacrylate successfully extracted information on the chemical composition and the monomer sequence. Then, the fractions of diad monomer sequences in an unknown sample were predicted to calculate the monomer reactivity ratios. Thus, the monomer reactivity ratios were successfully determined from a single sample.

The pH-responsive behavior of a core-crosslinked multiarm star polymer with an ionic poly(acrylic acid) (PAA) block segment in the arm was greatly affected by the arm chain sequence. Two types of star polymers with opposite block sequences was shown to differ sharply in the balance of hydrogen bonding and ionic repulsion between arm polymers, resulting in the different pH-responsive aggregation behaviors. The fundamental understanding gained by the present study deepens the insight into the solution properties of branched polyelectrolytes, which would expand the possibility for various applications.

Polymer and composite synthesis and structures. Formation of Graphene Matrix in Natural Rubber Dispersoid. In this study, the preparation of and characterization of a composite of natural rubber (NR) discontinuous phase (dispersoid) and graphene continuous phase (matrix) were carried out. Graphene (G) was prepared and grafted on rubber particle in latex stage in the presence of initiator tert-butylhydroperoxide and tetraethylene pentaamine with optimal amount of surfactant. The structure, the morphology, the mechanical properties, and the electromagnetic shielding of the resulting materials were superior compared to that of NR/graphene blend.

The anionic polymerization behavior of phenyl-substituted [3]dendralene derivatives, 2-phenyl[3]dendralene (2-P3D) and (Z)-1-phenyl[3]dendralene (1Z-P3D), was theoretically investigated using DFT calculation. The kinetic analysis based on the activation Gibbs free energy of the chain propagation showed that the anionic polymerization of 1Z-P3D proceeded with highly regioselective character; however, that of 2-P3D did not. By conformational and molecular orbital analyses, it was suggested that an effective conjugation of phenyl substituent with the chain end carbanion had a significant effect in the regioselectivity of the anionic polymerization of phenyl-substituted [3]dendralene derivatives.

Our work studied the effect of proteins on the graft copolymerization of vinyltriethoxysilane (VTES) on natural rubber (NR) latex. Stress at break of the graft copolymers was substantially higher when proteins were present; that is, the stress at break of fresh NR-graft-PVTES was higher than that of protein-free NR-graft-PVTES. Silica nanomatrix was formed more visibly in the presence of proteins, as observed by transmission electron microscopy. Furthermore, proteins were found to accelerate the formation of silica particles by forming hydrogen bonds with VTES molecules and enhancing hydrolysis with water molecules.

Poly(ether sulfone)-based functional ultrafiltration membranes were developed by employing chitosan (CS) and ammonium chloride (NH₄Cl) as antibacterial agents. A PES membrane was prepared and immersed in CS/NH₄Cl solutions at different NH₄Cl concentrations. The composite membranes show enhancement in the antibiofouling properties, where maximum bacteria-killing ratio (%BKR) values of 99.2 and 83.3% were observed against Staphylococcus aureus and Escherichia coli, respectively. The addition of CS/NH₄Cl not only modified the morphological structure of the PES membrane but also increased its hydrophilicity, porosity, and mechanical strength, suitable for ultrafiltration applications.