Volume 44, Issue 9

A novel hydrophobic association copolymer (PAMA) was synthesized by incorporating acrylamide (AM), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), cationic monomer (MEDDA), and methyl methacrylate (MMA). The properties of MMA copolymers with varying contents were analyzed using infrared spectroscopy, nuclear magnetic resonance spectroscopy, and scanning electron microscopy. Optimal overall performance of the solution was achieved when the MMA content reached 1.4 % w/w. Compared to pure PAAM (without MMA), the PAMA-1.4 % polymer exhibited superior viscoelasticity, temperature resistance, and shear resistance. This enhancement in PAMA performance can be attributed to the significant inhibition of intermolecular water film formation within the polymer matrix by MMA, effectively improving and regulating solution solubility while strengthening molecular chain interactions and enhancing the structural network strength of PAMA polymers. Additionally, the inclusion of MMA transformed rock surfaces from non-wetting to wetting conditions, thereby greatly improving oil displacement efficiency. In displacement experiments, PAMA-1.4 % performed better in terms of enhanced oil recovery, the recovery rate of 0.1 % w/w PAMA-2.4 % solution is only 7.78 %, while the recovery rate of 0.1 % w/w PAMA-1.4 % solution is 13.06 %.

The reuse of agricultural waste and the development of bio-based materials are the main strategies for solving the global energy crisis and environmental problems. Agricultural waste reeds containing natural nano-silica (SiO 2 ) were liquefied with PEG-400, Castor oil, and acid to produce reed-based polyols (R–P). The result shows that the liquefied product is a polyol with a hydroxyl value of 171 mgKOH/g, a viscosity of 1.221 Pa S, the number average molecular weight (Mn) of 1.202 kg/mol. Then reed-based two-component polyurethane emulsion (R-T-PU) and reed-based one-component waterborne polyurethane emulsion (R-O-WPU) with good glossiness and excellent mechanical properties were prepared. Because of the natural nano-SiO 2 in reed and castor oil, the coatings exhibit excellent mechanical properties and hydrophobicity. The results show that the series of reed-based polyurethane has excellent mechanical properties, a maximum hardness of 6H, good hydrophobic effect, a maximum contact angle of 109°, high thermal stability, and a maximum initial decomposition temperature can reach 299.1 °C. Therefore, the environmental protection bio-based polyurethane coating with excellent properties can be prepared with the reed, which is expected to replace fossil resources. It provides an experimental basis for the high-added-value utilization of reed.

Hydrogels possess excellent biological properties that make them ideal for biomedical applications. They are compatible with living cells and tissues because they can swell in the presence of water. In this study, we investigated the stability and biocompatibility of hydrogels. We synthesized and characterized N-acryl glycine (NAG) monomer and then synthesized its copolymer using the miniemulsion-polymerization technique, a soft-hydrogel method. To confirm the morphological properties of the dried hydrogel particles, we used the field emission scanning electron microscopy (FESEM) technique. We also investigated the rheological properties of the hydrogels for different concentrations to evaluate their mechanical strength and gel-like properties. Our findings indicated that the 10 % gel had superior strength and yield strain at all examined temperatures (30 °C, 37 °C, and 40 °C) compared to other concentrated gels. We systematically evaluated the biocompatibility of the hydrogel using three different cell lines: HEK 293T, RAW 264.7, and HeLa. Our cell line studies demonstrated that hydrogels are viable when exposed to a concentration of 0.5 mg/mL. Moreover, cell proliferation was observed at concentrations below 0.25 mg/mL. The MTT assay and rheology results suggest that hydrogel characteristics are more suitable for various biomedical applications, such as drug delivery and tissue engineering.

When skin comes into direct contact with the outside environment, it becomes extremely prone to injury and external factors can make wounds difficult to heal. Traditional medical dressings often cause secondary injury and are poorly resistant to infection. Hydrogels offer a promising alternative to overcome these difficulties. In this study, chitosan (CS)/gelatin (GEL)/polyvinyl alcohol (PVA) hydrogels were developed by chemical cross-linking and loaded with the drug kitasamycin (KM) for testing. The hydrogels’ in vitro drug release and wound-healing properties were assessed. For 48 h, the drug release from the hydrogel in vitro persisted, which was significantly longer than the release time of the KM solution. Antimicrobial activity tests showed that the loaded KM hydrogel maintained its bacteriostatic ability at the same concentration as the KM solution, and during in vitro bacteriostatic inhibition, the duration of bacteriostatic inhibition of the KM hydrogel was significantly prolonged compared to that of the KM solution. This confirms the controlled release capability of the hydrogel. In addition, the hydrogel reduced the wound size in mice by 96 % and histopathological tests showed complete re-epithelialization of the wound. The prepared hydrogels successfully demonstrated their potential ability to control drug release and promote skin wound healing.

Electromagnetic cooperative strategy has been proved to be an effective approach that can significantly decrease the matching thickness required for reflection loss. However, improving the electromagnetic wave (EMW) absorbing effectiveness with low matching thickness remains challenging for current single-phase absorbing materials. A layer-by-layer construction design is used in our study via a combination with iso-butyl isoprene rubber (IIR) and mixed polyurethane (MPU) as the matrix, with the single-wall carbon nanotubes (SWCNTs) and magnetic powder as fillers. This bilayer composite design resulted in a decrease in matching thickness and a shift in absorption bandwidth to higher frequencies by 40 %–50 %. Furthermore, the trilayer structure of MPU/IIR/MPU was found to stabilize permeability, enhance the thermal stability of the magnetism and improve the shielding effectiveness significantly. The thickness corresponding minimum absorption loss of the trilayer composites decreased and the absorption bandwidth of −10 dB widened by 50 % from 8.2 GHz–9.5 GHz to 10.2 GHz–12.4 GHz.

The flexibility and sensitivity of traditional sensors is hard to achieve unless wearable technology develops. Flexible piezoresistive sensor (FPS) is one of the solutions in the nondestructive health monitoring of living body. In the application of sensing devices for physiological or biochemical signals, fast feedback speed and accurate signal feedback are essential requirements for obtaining sensitive response signals. Additionally, the development of FPS has promoted the research of conductive materials that could be used in wearable devices. However, improving the performance of functional materials is an important way of effort for researchers. Recently, MXene as a new kind of 2D materials and their composites have made a tremendous impact in the field of sensors for wearable health sensors. Numerous conductive materials based 2D MXene could expedite their practical application in FPS by overcoming the present limitations of FPS such as poor responsivity, signal accuracy, and the narrower corresponding range. There has been plenty of breakthrough in the MXene-based FPS in the past several years. The main purpose of this paper is reviewing the recent development of MXene-based FPS and providing an outlook on the future development of it.

Antibacterial and oxygen barrier films were inventively prepared by blending very small loadings (<2 wt%) of chitosan oligosaccharide (COS) or chitosan (CS) in thermoplastic starch (TPS) and/or processing with supercritical carbon dioxide (scCO 2 ). Oxygen transmission rates (OTR) and free-volume-hole (FVH) characteristics of scCO 2- processed TPS/COS and TPS/CS blown films diminish to a minimum, as their COS or CS approach a specific compatibility limit content. The minimum OTR and FVH characteristics of scCO 2 -processed TPS/COS films are somewhat smaller than those of corresponding TPS/COS films without scCO 2 -assistance, and decrease further with decreasing COS molecular weights. The minimum OTR values of scCO 2 -processed TPS/COS blown films with COS’s molecular weight of 200 and 500 are only 4.1 and 4.5 cm 3 /m 2  × day × atm, respectively, and their antibacterial rates of Staphylococcus aureus are ≥97 %, which make them as promising antibacterial and oxygen barrier films having OTR ≦ 5 cm 3 /m 2  × day × atm. Among other things, longitudinal or transversal tensile strengths acquired for the properly scCO 2 -processed TPS/COS or TPS/CS films are ∼30 to ∼50 % higher than those of the TPS films. Dynamic mechanical relaxation results of these scCO 2- processed reveal that chitosan oligosaccharide or chitosan are compatible with TPS, as COS or CS contents are ≤ the compatibility limit value.

The processing of long glass fibre-reinforced thermoplastics results in considerable fibre damage, particularly during plasticising. By using thermoplastic foam injection moulding (FIM) with a constant blowing agent atmosphere, fibre damage during plasticisation can be reduced. This can be attributed to the reduction of the melt viscosity on the one hand and the influence of the melting behaviour on the other. Therefore, the influence of the FIM and the process parameters on the fibre length and the fibre length distribution are analysed and compared with the influence of the process parameters on the melt viscosity.