Polymer Journal最新文献

Solid-state NMR is one of the most powerful analytical methods for the structural characterization and dynamics of polymers. Owing to its intrinsically low signal sensitivity, however, analysis of trace chemical species supported on polymers remains challenging. Solid-state NMR with dynamic nuclear polarization (DNP-NMR) has recently attracted attention as a highly sensitive NMR measurement method for analyzing polymers. We recently investigated DNP-NMR for insoluble polymers, particularly cross-linked polymers, engineering plastics, and polymer-supported catalysts, and achieved high NMR signal sensitivity at a routinely accessible level. In this focus review, we present case studies on DNP-NMR measurements for a wide range of polymers.

This research showed that the self-healing properties of reversible crosslinked gels with host–guest inclusion complexes depended on the mobility of network chains and the recombination behaviors of reversible complexes, which were affected by changes in the water–glycerol solvent composition. The sticky reptation behaviors of the polymer chains were delayed by the recombination behaviors of reversible bonds. These behavioral characteristics were observed based on a dynamic viscoelasticity. Increasing the glycerol concentration in the mixed solvent decreased the surface tension and increased the mobility of the network chains because the recombination of the complex was slowed by the weak hydrophobic interactions between the host and guest molecules. Consequently, self-healing properties, such as re-adhesion at the cutting surface, were improved by the interdiffusion of polymer chains at the reattached interface. The strong hydrophobic interactions in pure water promoted the formation of complexes within the same cutting surface, thus decreasing the self-healing rates of the mechanical properties. In this study, the solvent was found to be an important parameter for controlling the self-healing properties of reversible crosslinked gels. The competition between the mobility of polymer chains and the recombination behaviors of reversible bonds controlled the self-healing properties of the gels with host–guest inclusion complexes.

Fluorene (Fl) derivatives are representative emitting motifs; thus, they are often installed into alternating π-conjugated copolymers (P(Fl-Ar)) as soluble polymeric emitters. Many researchers have focused on modifying the combined arylene units in P(Fl-Ar) derivatives to tune their optoelectronic properties; however, P(Fl-Ar) derivatives that contain fluorene units with functional groups at their sp² carbons remain limited. Here, we synthesize P(Fl-Ar) derivatives comprising sp²-chlorinated fluorene units via anodic chlorination using aluminum chloride (AlCl₃). The introduced chlorine atoms affect the optoelectronic properties of the pristine P(Fl-Ar) derivatives. Compared with the precursor P(Fl-Ar) derivatives, chlorinated P(Fl-Ar) derivatives exhibit longer maximum emission wavelengths.

We fabricated a volatile organic compound (VOC) sensor with a peptide–Au nanoparticle (AuNP)–TiO₂ nanocomposite in which AuNPs were linked with TiO₂-coated conductive peptide nanowires. The conductive peptide nanowires were formed between the AuNPs via self-assembly through the complexation of amphiphilic peptides, LESEHEKLKSKHKSKLKEHESEL, and Co(II). Furthermore, TiO₂ mineralization on the surface of the peptide nanowires yielded mixed crystals of rutile and anatase, which exhibited highly effective photolytic activity. In particular, the obtained TiO₂ exhibited three times greater photodecomposition activity in the unsintered state toward organic matter than did commercially available TiO₂. Next, we constructed a VOC sensor by immobilizing peptide–AuNP–TiO₂ nanocomposites on a comb electrode. The electrochemical properties of the nanocomposite changed drastically under light irradiation in the presence of VOCs, indicating transport of the VOC-decomposition-generated photoexcited electrons of TiO₂ to AuNPs through conductive peptide nanowires, which prevented electron–hole recombination. The obtained sensor exhibited a sensing range of 2–100 ppm for dichloromethane, which was used as a representative VOC. Therefore, nanocomposites made of AuNPs linked with conductive TiO₂ nanotubes may be highly effective for TiO₂-driven VOC decomposition. Moreover, we believe that this nanocomposite has high sensitivity for sensing VOCs.

Functional dyes exhibit intriguing properties in response to external stimuli related to their optical, electronic, structural, and energetic characteristics and enable unique stimuli-responsive functions in materials by collaborating with polymers, particularly when chemically incorporated into the polymer structures. As well as the structures and properties of functional dyes, polymers, assemblies, and materials, the interactions between these components are important to the functions of materials. In this review, we introduce our recent studies conducted in the past half decade on stimuli-responsive smart polymers and polymeric materials based on functional dyes that are chemically incorporated into the polymer structures, with a special focus on light, force, electric fields, and chemicals including water in a variety of external stimuli. For example, these polymers and materials offer switchable adhesion, mechanical actuation, and chemical sensing.

The development of bioactive scaffolds is essential for tissue engineering because of the influence of material physicochemical properties on cellular activities. Recently, we discovered that percolation-induced 4-arm polyethylene glycol (PEG) hydrogels achieved gel–gel phase separation (GGPS), which has tissue affinity in vivo. However, whether the 4-arm structure is the optimal configuration for the use of PEG hydrogels as scaffolds remains unclear. In this study, we investigated the effect of an increased branching factor on GGPS. Compared with the 4-arm PEG hydrogel, the 8-arm PEG hydrogel presented a greater degree of GGPS and increased hydrophobicity. We introduced the RGD sequence into PEG hydrogels to directly assess the biological activity of GGPS, with a particular focus on its effects on the activity of bone-forming osteoblasts. Although the 8-arm PEG hydrogel did not enhance cell adhesion, it enhanced osteoblast differentiation compared with the 4-arm PEG hydrogel. Therefore, the 8-arm PEG hydrogel mediated by GGPS shows promise as a scaffold for osteoblast differentiation and holds potential as a foundation for future advancements in bone tissue engineering.

Multifunctional hydrogel materials are being increasingly used in wearable sensing devices and biomedical applications, but the comprehensive performance of hydrogel materials must be further developed. To prepare hydrogels with better self-healing properties, biomacromolecules such as sodium alginate and carboxymethyl chitosan were used as raw materials by combining the dynamic imine bonding network formed by both materials with the coordination bonding network formed by acrylic acid and aluminum ions. The double network structure of the hydrogel provides the hydrogel with excellent self-healing properties (up to 127% recovery of toughness after self-healing) and good mechanical properties with a fracture strain of 3787%. Substances with antimicrobial properties in the hydrogel network inhibited the growth of E. coli and S. aureus. In addition, the hydrogel has good electrical conductivity with a conductivity of 1.41 S/m. This study examined multiple properties of the hydrogel and provides a reference for the application of this material in practical application scenarios.

Heat insulators are key materials for efficient energy use and reduction of CO₂ emissions. Recently, we examined cross-linked polymethylsilsesquioxane (MSQ) for use as the basic structure of heat-resistant insulation materials. In this study, we prepared MSQs with different cross-linking units and examined the effects of their structures on the heat resistance and heat insulation properties. Among those, MSQ linked by diethynylbenzene had sufficiently low thermal diffusivity and moderately high heat resistance. We also showed their structure–thermal property relationships. Although other influencing factors could exist, the rigidity, π‒π interactions, and bulkiness of the cross-linking units were found to predominantly influence the thermal properties. These findings will lead to new molecular designs for polysilsesquioxane (PSQ)-based heat-resistant heat insulators with high performance.

The surface modification of carbon materials is an effective method for enhancing the properties of carbon-based functional materials; particularly, the use of a polymer coating is advantageous owing to its intactness and simplicity. Polybenzimidazole (PBI) has been used to modify carbon surfaces, yet its adsorption behavior has not been thoroughly examined. In this study, the adsorption kinetics and thermodynamics of PBI adsorption on various types of carbon black with different surface morphologies and chemical compositions were analyzed via isotherm measurements. To determine the effects of the polymer, its adsorption behavior was compared to that of the PBI monomer (1,3-bis(1H-benzo[d]imidazol-2-yl)benzene (referred to as the PBI-unit)). The surface adsorption of PBI was slower than that of the PBI-unit; however, PBI exhibited a greater adsorption capacity. The PBI adsorption is an entropy-driven process, whereas PBI-unit adsorption is enthalpy-driven. The adsorption of PBI was more thermodynamically favorable on carbon surfaces with higher crystallinity (lower oxygenation) owing to the easier detachment of solvent molecules from the carbon surface, leading to a higher adsorption constant.

In this study, polymers with different copolymerization composition ratios of α-chloro-ε-caprolactone (α-ClCL) and ε-caprolactone (ε-CL) were prepared using α-ClCL, which can polymerize on its own. The copolymers were prepared by using trimethylolpropane as the initiator, and acryloyl groups were added to the polymer ends to form macromonomers capable of cross-linking reactions. The functionalized macromonomers were confirmed to possess shape-memory properties when cross-flinked in film form by heat. The composition of the functional groups in the macromonomer could be adjusted by changing the ratio of α-ClCL to ε-CL used in the copolymerization. In addition, the chloro group introduced by α-ClCL was converted into an azide group. Both the cross-linked film with chloro groups and the film converted to azide groups prepared in this study exhibited shape-memory according to the softening point of the film. Through fluorescence microscopy, it was confirmed that the converted azide groups were modified with alkylated rhodamine B based on the click reaction. Furthermore, azide-assisted films are expected to add various functions through click reactions in the future.