Polymer Science, Series A最新文献

In this study, polyaniline was synthesized as a potential antibacterial agent and integrated into κ‑carrageenan as a biopolymer matrix. Polyaniline samples were polymerized at 0°C and room temperature using a chemical oxidative method with hydrochloric acid as a dopant. Ex-situ polymerization was employed, incorporating polyaniline into κ-carrageenan with glycerol as a plasticizer to produce composite films. These films were characterized by FTIR, electrical conductivity, tensile test and TGA analyses. The addition of polyaniline enhanced the conductivity of pure κ-carrageenan film and improved its thermal stability, although mechanical properties such as tensile strength, modulus and elongation at break decreased. The antibacterial activity of the films was evaluated using an agar disc diffusion method against Gram-positive S. aureus and Gram-negative P. aeruginosa. Composite film demonstrated optimal antibacterial activity, achieving a 37.3 ± 2.2% against S. aureus after 24 h. The antibacterial mechanism was attributed to electrostatic interactions between cationic N⁺ from the quinoid structure of polyaniline and anionic bacterial membrane of S. aureus, causing disruption of the bacteria cell. Composite film retained antibacterial activity against S. aureus for up to 48 h. These findings suggest that produced composite films hold potential as wound dressings due to their antibacterial properties.

This study investigated the properties of a blend made from two copolymers: poly(benzaldehyde-co-thiophene) (PBT) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). PBT was first synthesized via oxidative coupling of thiophene and benzaldehyde monomers. The synthesized PBT was then mixed with commercially available PHBV in a 50/50 ratio using solution casting. The X-ray diffraction revealed the amorphous nature of PBT and the semi-crystalline nature of PHBV. The Infrared spectroscopy confirmed the presence of both materials in the blend. UV–Vis analysis showed characteristic absorption peaks for both polymers: PBT displayed π–π* transitions and a π–π* transition related to its semiconducting properties, while PHBV exhibited peaks associated with the carbonyl group. The thermogravimetric analysis demonstrated the thermal stability of PBT compared to the degradability of PHBV. The differential scanning calorimetry revealed a decrease in the blend’s melting temperature and enthalpy of fusion compared to pure PHBV, indicating hindered crystallization in the blend. The scanning electron microscopy visualized the distinct morphologies of the two copolymers within the blend, suggesting their immiscibility.

A wide variety of thermal interface materials (TIMs) used in the electronics semiconductor industry, but heat dissipation is still a problem. Meeting this challenge requires the development of new polymer-based composite materials with improved thermal conductivity. In this study, carbon fiber (CF)/Silicon carbide (SiC) hybrid filler-loaded polypropylene (PP) matrix composites were produced. Thermal properties of composites were investigated by the simultaneous differential thermal analysis, differential scanning calorimeter and thermal conductive measurement system. The mechanical properties of composites were measured by dynamic mechanic analysis and universal mechanical analysis test systems. The molecular structure changes and crystallinity of composites were analyzed by X-ray diffraction analysis. The composites microstructure was identified by scanning electron microscopy technique. The electrical conductivity of the composites investigated with the electrical conductivity measurement technique. The addition of CF into the SiC particles improved thermal degradation and mechanical properties of composites according to only SiC loaded PP matrix. The mixture of 3% CF and 47% SiC particle by weight into the PP matrix improved the thermal conductivity of composites almost 40% than the 50% SiC loaded PP. The viscoelastic properties and the durability of the composites increased with the CF addition.

Proton-conducting membranes are widely used in various electrochemical systems. The content and state of water in membranes have a significant impact on their properties. Therefore, studies of the interaction of membranes with water are relevant and are the subject of many works in the scientific literature. This paper presents data obtained by studying the dynamics and characteristics of water saturation in three types of membranes consisting of ionomers with a long side chain (Nafion and MF-4SK) and a short side chain (Aquivion). The dynamics of hydration were studied using electron spectroscopy in the near ultraviolet and visible regions, differential thermal analysis, and gravimetry. It has been shown that the process of hydration of different membranes occurs in distinct ways, although it has common patterns, the main one of which is the presence of two-stage hydration: 1. rapid water absorption and 2. slow rearrangement of the membrane structure. The values of equilibrium water content in air-dry membranes and their specific moisture capacity are provided.

Amphiphilic dendrimers, which contain segments of hydrophobic and hydrophilic nature in one molecule, have attracted increasing attention due to their high potential for use in a variety of practical applications, in particular as surface modifiers and molecular nanocontainers for drug delivery. A thorough comprehension of the structure-composition-properties relationship in these systems is of paramount importance for the targeted design of new materials. In this paper, we examine the conformational behavior of amphiphilic G2–G4 carbosilane dendrimers with hydroxyl-modified terminal groups in toluene and aqueous solutions through atomistic molecular dynamics simulations. By explicitly simulating the solvent, we were able to elucidate the effect of the solvent nature on the distribution of various structural elements, such as branches and terminal groups, inside the dendrimer as a function of generation number. In aqueous solutions, the dendrimers adopt a dense globular conformation with a large fraction of hydroxyl groups concentrated in the periphery and participating in hydrogen bonding with water molecules. In toluene, the dendrimers swell, the solvent uptake reaches 30–40 vol %, which is in good agreement with existing experimental data. In the hydrophobic medium, hydroxyl groups form intramolecular hydrogen bonds, resulting in clusters of preferentially linear geometry. The cluster size distribution is very broad and there is a non-zero probability of clusters containing almost all OH groups of the dendrimer. The results obtained are important for a better understanding of the self-assembly and surface activity of amphiphilic dendrimers and for the design of new materials based on them.

Polymer–polymer composites based on poly(ether ketone ketone) and polyphenylenesulfone have been investigated for the first time. It has been shown that the blends exhibit a single relaxation vitrification transition up to the 50 : 50 composition, which evidences good compatibility of poly(ether ketone ketone) and polyphenylenesulfone in the amorphous phase. Slight phase separation has been observed at the 50 : 50 and 30 : 70 ratios, reflected in significant broadening of the glass transition regions in the differential scanning calorimetry and dynamic mechanical analysis curves. It has been shown that an increase in the content of polyphenylenesulfone leads to an increase in the glass transition temperature and the heat deflection temperature. Furthermore, polyphenylenesulfone has prevented the crystallization of poly(ether ketone ketone), which has been accompanied by an increase in the crystallization temperature and a decrease in the degree of crystallinity. It has been revealed that the introduction of polyphenylenesulfone leads to a gradual decrease in the mechanical parameters measured at low strain, the changes of which have followed the additivity rule. On the contrary, the strain has been more sensitive to the phase structure; it has been significantly decreased upon the appearance of the phase separation, more pronounced at the 50 : 50 composition.

The coating based on chitosan with rutin and 2-hydroxypropyl-β-cyclodextrin for mango preservation has been prepared using the direct immersion method. The results of FTIR and FR-SEM indicated that an inclusion complex between rutin and 2-hydroxypropyl-β-cyclodextrin was obtained in the chitosan matrix polymer. Besides that, the hydrogen bonds of chitosan, rutin, and 2-hydroxypropyl-β-cyclodextrin were formed. Adding rutin and 2-hydroxypropyl-β-cyclodextrin with 0.5 and 1.25% content, respectively, in the 2% chitosan solution created the solution with the best preservation ability within the research range. A coating with a thickness of about 14 µm is capable of increasing the preservation time up to 14 days, compared to 7 days for uncoated samples and 10 days for samples coated with 2% chitosan solution. The results of several biochemical indicators, such as mass loss, vitamin C content, respiration intensity, and ethylene production during storage, demonstrated the preservation ability of the CCR2 coating for mangoes.

The stability of a pre-stretched and fixed cylindrical thread of weakly crosslinked polymer gel against varicose perturbations has been analyzed. The influence of capillary forces, gel elasticity, and interactions on the dynamics of the perturbations has been investigated, and a criterion for thread instability has been formulated. A dispersion equation has been derived, and based on this equation, the fastest-growing mode of perturbations has been determined, along with its growth rate as a function of the macroscopic properties of the gel and the thread radius.

The rheological properties of suspensions based on paraffin and LDPE, in which polyphenylene sulfone powder is dispersed, intended for powder injection molding and 3D printing were studied. Compositions with a polymer content of up to 50 vol % are pseudoplastic liquids that lose their flow ability upon reaching 60 vol %. Suspensions with 30 and 40 vol % polyphenylene sulfone have optimal technological properties during injection molding, combining the required rheological properties and strength of products. At the same time, compositions with PE have sufficient fluidity only at 180°C, while elastic deformations dominate at lower temperatures. The best quality of 3D printing is achieved using a composition based on a matrix of paraffin and PE (30 : 70), with a polyphenylene sulfone content of 40 vol %.

Porous sponges of polyvinyl alcohol (PVA) can provide moist environment, protect wound from microbial attack, absorb excess exudates, exchanges oxygen and water vapor, and deliver therapeutic agents to the wound site. However, more information should be gained about comparing properties of crosslinked and non-crosslinked PVA sponges and the impacts of adding other biopolymers such as sodium alginate (ALG) and sodium carboxy methyl cellulose (CMC) on the wound dressing properties and drug release from these composite sponges. Here we have prepared and characterized PVA composite sponges loaded with deferoxamine (DFO), a drug with prominent wound-healing effects, to manage exudative chronic wounds. The impacts of crosslinking by freeze thaw cycles and adding CMC or ALG to PVA sponges were evaluated on morphology, mechanical strength, crystallinity, porosity, fluid uptake, water vapor transmission rate, water vapor loss, pH, blood compatibility, and controlling drug release. The produced sponges differed in crystallinity of PVA, pore shape, size, and interconnectivity. Crosslinked composite sponges showed better porosity than non-crosslinked ones and had higher porosity (>80%) with interconnected macropores in the appropriate size range for cell attachment. All sponges were hemocompatible with less than 1% hemolysis and had good physical integrity and flexible texture. The water handling properties were also affected by crosslinking. Although all prepared sponges showed high water absorption in the range of 450–650% within 6 h, the crosslinked sponges showed slower water uptake than non-crosslinked samples. Prepared sponges could control DFO release with 60% cumulative release over 24 and sponge composition and crosslinking influenced DFO release.