Original Article in 2020

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.

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%.

(2 × 4)-Type tetra-PEG ion gels were prepared through a copper-free azide–alkyne cycloaddition reaction between tetra-branched poly(ethylene glycol) and linear tetra(ethylene glycol). The tensile tests showed that the reaction efficiency of the cross-linking was over 90%. The prepared ion gels exhibited high mechanical toughness and stretchability characteristic of tetra-PEG gels. The electrochemical window of the ion gels was the same as that of the ionic liquid inside the gel. The ionic conductivity of the ion gel (30 wt% polymer concentrations) was 8.9 × 10⁻⁴ S cm⁻¹ (25 °C, anhydrous conditions).

We prepared hybrid porous membranes by the W/O miniemulsion templating method. First, centrifugal accumulation of water nanodroplets and subsequent polymerization of the oil phase were carried out to form porous membranes. The size of the nanodroplets was tuned by the surfactant concentration to control the pore size of the membranes. We could produce pore morphologies such as closed-cellular, open-cellular, and bicontinuous structures by tuning the volume fraction of the nanodroplets. Next, conjugation of gold nanoparticles over the inner pore walls was carried out by utilizing the reducing ability of surfactants.

Composites of nylon 6 and large amounts of alumina nanoparticles were prepared to investigate nylon 6 at its interface with alumina. DSC curves obtained by heating and cooling the slowly cooled samples indicate decreases in melting and crystallization temperatures. The melting enthalpy and XRD patterns show a decrease in the degree of crystallization with the addition of alumina. The IR spectra suggest that hydrogen bonds were enhanced at the interface.

Microtubules (MTs) consisting of tubulins are important targets of drugs for MT-related diseases. We have previously designed a linear Tau-derived peptide (TP) that binds to the interior of MTs. In this article, a cyclic TP (TCP) was developed for enhanced binding to tubulin and stabilization of MTs. The fluorescently labeled TCP exhibited a remarkably enhanced binding affinity to tubulin compared to the linear TP. The stabilization of MTs by binding of TCP was demonstrated, such as formation of typically unstable MTs in the presence of guanosine triphosphate.

Stereocomplex (SC) crystals of polylactide were formed in carbon black-filled Poly(l-lactide) (PLLA)/Poly(d-lactide) (PDLA) composite with 10 and 20 wt% of PDLA during melt blending at the temperature between the melting points of homocrystal and SC crystal. From the analysis of Morisita’s index (I_δ) determined from scanning electron microscopy images and through direct current measurements and alternating current impedance measurements, it was revealed that the increase in the number of SC crystals formed during melt blending improves the filler distribution to achieve a uniform pattern.

We proposed a new method to functionalize supramolecular peptide nanofibers using fiber-binding peptides screened from a phage peptide library. The RGDS-conjugated fiber-binding peptides significantly enhanced the adhesion of 3T3-L1 cells on E1Y9 nanofibers through noncovalent modification of E1Y9 nanofibers. This noncovalent modification using fiber-binding peptides was also effective for functionalization of E1Y9 hydrogels as cell culture materials that promoted the proliferation of 3T3-L1 cells. The functionalization of supramolecular peptide nanofibers using molecular recognition peptides will be a powerful tool for the development of functional materials.

The linear viscoelastic properties of block copolymer solutions forming hexagonal close-packed cylindrical domains were investigated by using a rheo-optical method. Based on the modified stress-optical rule, the complex shear modulus was separated to four relaxation modes. Considering the sign and magnitude of the stress-optical coefficient associated with each mode, the four modes were assigned to (1) reorientation of corona chains, (2) reorientation of core chains, (3) deformation of domains, and (4) reorientation of grains. The results were compared with those for spherical domains.

Multicomponent hydrogel systems were formed using combinations of three self-assembled peptide based gelators with motifs inspired by fibronectin, collagen, and laminin, respectively. After a systematic study on the how the properties of hydrogels correlate with cell growth and proliferation, it was found that cell growth was significantly impacted by the hydrogels’ resistance to strain which was defined by their crossover point. This indicates that the ability of the gel to efficiently store the work of deformation during cell division is the most important factor for cellular proliferation.