Polymer Journal最新文献

Wollastonite (W)/carbon black (CB)/chlorinated polyethylene (CPE) conductive composites were prepared via melt compounding using CB and wollastonite as fillers and CPE as the matrix. To analyze the internal structure of the material and examine how changes in crystallinity affect the positive temperature coefficient (PTC) behavior of the composites, several characterization techniques were employed. These methods included scanning electron microscopy, X-ray diffraction, and differential scanning calorimetry. Each method provided insights into the structural adjustments and their implications for the electrical properties of the material. Special attention was given to the influence of the wollastonite content on the electrical conductivity of the composites. The results demonstrated that the lowest room-temperature resistivity (1.66 Ω·cm) was achieved with 15 wt.% wollastonite doping after 1 h of heat treatment. At the same time, the PTC strength increased to 4.7.

Photodynamic therapy is useful due to its high antitumor efficacy, spatiotemporal selectivity, and noninvasiveness and has garnered significant attention in the field of cancer treatment. When photoexcited by light irradiation, photosensitizers produce reactive oxygen species (ROS) that damage tumor tissues. However, photosensitizers can also accumulate in normal tissues, leading to side effects such as skin photosensitivity. To mitigate these side effects, we report the development of chlorophyll‒peptide conjugates as tumor-selective photosensitizers. These conjugates bearing histidine and lysine residues self-assemble into nanoparticles that are expected to accumulate selectively in tumors and reduce ROS generation through self-quenching under the neutral conditions typical of normal tissues. In contrast, these aggregated conjugates partially disassemble under weakly acidic conditions, such as those found in tumor tissues, resulting in phototoxicity. We anticipate that these acid-activatable conjugates have the potential to serve as cancer-selective photosensitizers, thereby reducing phototoxicity in normal tissues.

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.

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.