Research articles

A degradable cross-linked polybutadiene was synthesized using a peptide-based cross-linker. As a degradable cross-linker, we synthesized poly(L-cysteine) (polyCys) by papain-catalyzed chemoenzymatic polymerization. The thiol-ene reaction between polybutadiene and polyCys was conducted in the presence of a radical initiator, resulting in the formation of an insoluble polybutadiene gel. The successful cross-linking and network formation was confirmed by Raman spectroscopy and viscoelastic analysis. Dynamic viscoelastic measurements of the cross-linked polybutadiene revealed the disappearance of slow relaxation mode. The polyCys-linked polybutadiene underwent degradation through acidic hydrolysis, allowing the recovery of soluble polybutadiene.

This study explores enhanced electrical properties in conductive polymers, particularly PEDOT:PSS, by creating multilayered films. Initial findings show a sheet resistance of 1639 Ω□^-1 for a single layer, but applying three additional layers reduces it to 29 Ω□^-1, boosting conductivity from 2.6 to 18.3 Scm^-1. Similar improvements are observed with formulations containing Tween 80. Analysis via X-ray diffraction and Raman spectroscopy indicates increased crystalline order and a benzoid to quinoid shift. Surface profiling reveals growing roughness with additional PEDOT:PSS layers, partially mitigated by Tween 80.

Tributylborane-initiated graft polymerization of methyl methacrylate on a poly(vinylidene fluoride) film was successfully achieved. The reaction was affected by the temperature and concentration of tributylborane, and a 41% graft yield was obtained under the optimized conditions. This value was higher than those obtained with other methods. This method facilitated modifications of only the surface of the poly(vinylidene fluoride) film, which was confirmed by IR spectroscopy and cross-section observations. New physical properties were added to the surface, such as hydrophilicity.

Ester free type trimethylene carbonate derivatives bearing bulky aromatic groups were designed and synthesized, including one or two benzyl groups, diphenylmethyl groups, and triphenylmethyl groups. The mechanical properties of the polymers were estimated by compressive test, resulting in around 0.3MPa at most. The degradation behaviors were also evaluated under Lipase solution and 0.01M NaOHaq. for several weeks, revealing the substituents influenced on the prevention of degradation at most cases. The degradation behavior was slowly observed, which were analyzed by weight loss, SEM images, SEC, TGA, and DSC.

The effect of radiation-induced graft polymerization (RIGP) on abaca fibers was evaluated for composite reinforcement. Using grafted fibers improved composite properties, especially when RIGP was carried out under reversible addition-fragmentation chain transfer (RAFT) mechanism. Controlled chain growth of grafted polymer could be achieved by RAFT-RIGP and this led to the highest improvement in mechanical strength versus pristine fibers and those modified by conventional RIGP. These findings show the capability of RAFT-RIGP to optimize the effectiveness of natural fibers in the composite industry.

Monomer sequence transformation and reversible polymerization–depolymerization control were achieved in the cationic copolymerization of 2-methyl-1,3-dioxepane and γ-butyrolactone by vacuuming or temperature change. The removal of monomers from the polymerization solution with a vacuum pump promoted depolymerization, resulting in a transformation to pseudo-alternating copolymers and subsequent oligomer formation. Heating the polymerization solution also promoted a similar monomer sequence transformation and oligomer formation, while cooling led to the polymerization of monomer molecules generated via depolymerization.

Elastic moduli of nano-dispersed elastomer domains in injection molded isotactic polypropylene (iPP)/ethylene-co-octene elastomer (EO) binary blends were investigated by an atomic force microscopy. The EO domains were highly elongated to the flow direction. The elastic modulus distribution of the EO domains was quite different depending on the annealing conditions.

Poly(dopamine) (PDA) was investigated as a primer to enhance adhesion in flexible optoelectronic devices using the conducting polymer PEDOT:PSS. PDA improved wettability on polypropylene (PP) but reduced it on poly(ethylene terephthalate) (PET). However, PDA enhanced the quality and adhesion of pristine PEDOT:PSS and PEDOT:PSS/Tween 80 films on glass, PP, and PET. Crucially, it did not negatively affect sheet resistance of PEDOT:PSS/Tween 80 films, establishing its suitability as a primer for flexible substrates. This research addresses a key challenge in utilizing PEDOT:PSS in flexible optoelectronics, enhancing its performance on various substrates.

We determined intrinsic viscosity for polystyrene (PS) samples with a wide range of molecular weight in d-limonene, which attracts interest as an environmentally friendly solvent for PS. By analyzing the experimental data obtained in d-limonene using the helical wormlike chain model with and without the excluded-volume effect, solvent quality of d-limonene for PS was quantitatively evaluated. Consequently, it was concluded that d-limonene belongs to the category of medium solvent, which is intermediate between good solvents like toluene and poor solvents like cyclohexane, for PS.

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.

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.