Articles in 2023

A new concept for controlling the energy level of conjugated materials without extending the π-conjugated system is described. By performing aza-substitution at the “isolated frontier molecular orbitals (FMOs)”, which are defined in this manuscript, one energy level of FMOs can be selectively and efficiently lowered. Based on this protocol, advanced conjugated polymers with pure-blue or near-infrared luminescent properties were obtained.

Crystalline porous molecular frameworks formed through intermolecular hydrogen bonding calling hydrogen-bonded organic frameworks (HOFs) have recently been investigated as a new family of functional porous materials. In this review, HOFs composed of tritopic, tetratopic, and hexatopic carboxylic acid derivatives, which form H-bonded network such as those with hcb, sql, and hxl topologies depending on the numbers, positions, and orientations of the carboxy groups and conformational flexibility of the molecular skeletons, are reviewed by considering structural aspects such as isostructurality.

For uniform and flat materials, heavier plates show higher sound insulation performance because of the mass law. Acoustic metamaterials with periodic resonance structures have attracted attention as ultra-lightweight sound insulators that can break the mass law limit. Recently, practical acoustic metamaterial sheets that allow high-throughput fabrication and single-step implementation on target objects have been developed based on polymer materials. In this Focus Review, the polymer-based material design, the control of acoustic functions based on polymer properties, and applications as sound insulators and vibration dampers are described.

Thermal curing of maleimidobenzoxazines (MB-Rs) with n-butyl, 2-ethylhexyl, allyl, and phenyl substituents was carried out in the presence of tetrafunctional thiols with pentaerythritol and glycolurea cores. The thermosets were prepared by the following curing processes: directly curing the mixtures at 140–160 °C and postcuring the building block. The effects of the network polymer structures on the thermal stability and mechanical properties of the thermosets were investigated. The thermosets showed excellent decomposition temperatures, i.e., T_d5 = 215–309 °C and T_d50 = 318–587 °C. The mechanical properties were modified by introducing a 2-ethylhexyl group, and stretchable and bendable thermosets were obtained.

Series of propylene (C3) and hexylene (C6)-linked tripod-shaped polyhedral octasilsesquioxane (POSS) derivatives were prepared corner-opening type POSS (COPOSS) with completely condensed POSSs (CC-POSSs). The annealed cast films of the tripodal POSSs were optically transparent, except those consisted of the phenylsubstituted CC-POSS, which were rather turbid. The tripodal POSSs showed endothermic peaks corresponding to melting (Tm) and suggest that including the phenyl-substituted CO-POSS unit reduced Tms compared with the isobutyl-substituted CO-POSS.

The effects of the addition of a hyperbranched polymer (HBP) on the degradability characteristics of linear polyglycolide (PGA) fiber mats. It was revealed that HBP acted as a plasticizer, especially in underwater environments. The weight loss of the PGA fiber mats was accelerated with increasing HBP content. Considering that the structural changes in the PGA crystals depended on the feed amount of HBP, it was claimed that HBP promoted PGA degradation in both the amorphous and crystalline phases.

Lentinan (Len) is a linear (1,3)-β-d-glucan with two of its five main-chain glucose-bearing (1,6)-β-d-glucan side chains and has been clinically used for cancer treatment in combination with chemotherapy. In this paper, a structural analysis of Len was conducted using SAXS, GPC, and ¹³C quantitative NMR techniques, and a comparative study with other β-glucans was performed. The complexation between dA₄₀ and Len caused the hypochromic effect. Len and dA₄₀ showed a similar complexation with that of SPG; two main chain glucoses bind to one dA moiety by GPC.

The higher-order structures of polymer-brush-modified nanoparticles (PSiPs) in ionic liquids were analyzed using ultrasmall-angle X-ray scattering. The self-assembly of the PSiPs was entropy-driven. The transition threshold concentration of the PSiPs was understood through the Kirkwood–Alder transition by considering the effective particle sizes. The random hexagonal close-packed structure in the concentrated-polymer-brush regime exhibited the characteristics of hard spheres, whereas face-centered cubic and body-centered cubic structures in the semidilute-polymer-brush regime reflected softening of the interparticle potential.

Narrow size distributions of spherical polyacrylic acid (PAA) particles are produced through precipitation polymerization without the need for stabilizers or emulsifiers. In this study, we employed small-angle X-ray scattering (SAXS) to investigate the polydispersity index (PDI) associated with the molecular weight distribution of the particles. By fitting the SAXS profiles, we were able to determine particle sizes, standard deviation, and the PDI with high precision. Our findings from SAXS confirmed that the PAA particles are monodisperse, both statistically and quantitatively, with a PDI of less than 1.05.

Peptides are versatile molecular tools with molecular recognition capabilities, high designability, and the capacity for self-assembly. In this focus review, the construction of new bio-nanoarchitectures using our peptide-based technologies is described. First, the construction of functional microtubules was achieved by molecular encapsulation using a Tau-derived peptide. Second, light-induced peptide nanofiber growth was used for the development of artificial motile systems of micrometer-sized spheres. The development of bio-nanoarchitectures by these peptide-based approaches is useful for understanding, mimicking, and controlling natural nano/microstructures.

In the first part of the review, continuous and length-controllable discrete one-dimensional channels, two-dimensional sheets, and three-dimensional vesicles, bulk-state complexation based on the versatile functionalization of pillar[n]arenes are discussed. In the second part of the review, functionalized pillar[n]arene crystals showing guest-responsive changes in color, state, and water contact angle, as well as serving as reaction media for the spontaneous polymerization of cyclic monomers are discussed.

The density-dependent changes of avidities between Siglec-8 and the glycan ligand of the α(2 → 6)-sialyl-6-sulfo-N-acetyllactosamine derivative (1) were investigated for the first time. The SAM surfaces with different glycan densities were constructed by changing the ratio of 1 and 3,3′-dithiodipropionic acid (DTPA) on the gold electrode of the quartz crystal microbalance (QCM). Next, we measured the apparent K_D values of 1 with Siglec-8 on the SAM surfaces by the QCM to investigate the effect of the glycan density on the avidity of the Siglec-8 interaction. The results obtained in this study suggest that Siglec-8 has an optimal glycan density (~9.2 × 10² molecules μm⁻²) for preferred interactions.

Double-hydrophilic block copolymers composed of a water-soluble poly(carboxybetaine acrylate) and a water-insoluble poly(2-methoxyethyl acrylate) (PCBA2_n-b-PMEA_m) produced particles in dilute aqueous solutions and microphase-separated structures in concentrated aqueous solutions. The microphase-separated structures were associated with the volume fraction and molecular weight-dependent water solubility of the PMEA chain. The morphology of the microphase-separated structure was independent of the polymer concentration, probably because the block copolymer aggregates were isolated as coacervates. The morphology was tolerant to NaCl concentration due to the nonelectrostatic aggregation of PMEA.

Postfunctionalization of poly(vinyl alcohol) (PVA) was performed in supercritical carbon dioxide (sc-CO₂) for the selective functionalization of the amorphous region. The crystalline region was retained in the amorphous-selective acetylated PVA. The oriented structure of crystallites of the drawn PVA was maintained even after acetylation in sc-CO₂. Moisture adsorption behaviors affected the crystalline structure of PVA acetylated in sc-CO₂. The PVA acetylated in sc-CO₂ included a larger number of water molecules under humid conditions, but the increase in thickness after water adsorption was smaller than that of randomly acetylated PVA.

Using temperature variable SAXS and WAXS techniques, nature of thermal expansion behavior of injection molded iPP was investigated. The SAXS and WAXS provided the thermal expansion in amorphous phase and the one in crystal axes, respectively. The bulk thermal expansion was fully accounted for by the combination of them. It was found that the thermal expansion from the amorphous phase contributed significantly to the bulk thermal expansion.

The isothermal crystallization behaviors of blends of cyclic polyethylene (C-PE) and linear polyethylene (L-PE) in a quiescent state were investigated. This figure shows the inverse of the half-crystallization time (1/t_1/2) as a function of the weight fraction of L-PE (Φ_L-PE) at different degrees of supercooling (ΔT). The 1/t_1/2 showed a minimum at Φ_L-PE = 30–40 wt%, irrespective of ΔT. By considering the experimental relationship between 1/t_1/2 and Φ_L-PE, we speculated that the suppression of crystallization in the blended system was caused by a novel entanglement formed by the penetration of the L-PE chain into the C-PE chain.

Iron-modified catechol hydrogel treatment with EDTA is investigated at three immersion pH levels – pH 3, 5, and 7. The introduction of EDTA facilitates the chelation of Fe³⁺ ions, resulting in a modified hydrogel with enhanced metal ion binding capacity. The functionalized catechol chitosan hydrogel after the treatment exhibits potential applications in biomedical and environmental fields. This research sheds light on the development of versatile hydrogel materials with tailored properties, showcasing the capabilities in diverse applications where metal ion interactions play a crucial role.

Coordination polymerization of a series of 2-substituted-[3]dendralenes was investigated. No polymerization was observed for 2-trimethylsilyl[3]dendralene, whereas 2-phenyl[3]dendralene polymerized by CpTiCl₃ as a catalyst and modified methylaluminoxane as an auxiliary catalyst to generate polymers that became insoluble in the process of isolation. Additionally, the coordination polymerization of 2-hexyl[3]dendralene was conducted using a CpTiCl₃/modified methylaluminoxane catalyst to produce polymer with mainly a trans-4,6 structure, which differs from that of the polymer obtained via anionic polymerization. The copolymerization of isoprene with 2-hexyl[3]dendralene was also examined.

Polymer composites containing citric acid-modified cellulose (CAC) and hydrogen bonding moieties showed significant increases in mechanical toughness. In particular, an appropriate ratio of hydrogen bond donors and acceptors in the secondary linear polymer (poly(2-methoxyethyl acrylate)) maximized the toughness. The hydrogen bonds affected the phase. The maximum toughness was achieved for an amorphous structure without obvious phase separation.

Polymers that can depolymerize into their constituent monomers are desirable sustainable materials, but demonstrations have focused on linear polymers. Here, a depolymerizable graft copolymer thermoplastic material is prepared by copolymerizing poly(L-lactide)-based and margaric acid-based trans-cyclobutane-fused trans-cyclooctene macromonomers. The two types of macromonomers are incorporated randomly. Proper thermal treatment is required to maximize, or even to observe, crystallinity in the microphase separated that persists over a range of temperature. The physical states of the soft and hard domains significantly impact the material’s tensile properties.