Macromolecular Materials and Engineering最新文献

In the study, a new strategy is presented to make PLGA (poly lactic-co-glycolic acid) and POEGMEMA (poly(oligo(ethylene glycol) methyl ether methacrylate)) based biodegradable and biocompatible tissue scaffold via a new physical cross-linking method. The advantage of brushed structure of POEGMEMA polymer and the hydrophobic character of PLGA polymer is taken to make physically entangled network in aqueous media. The hydrophobic nature of PLGA allows to get scaffolds even at low ratio of PLGA (25%, w/w) when using POEGMEMA (yield: 86%). This strategy gives robust polymeric networks in aqueous media without using chemical reactions through high hydrophilic polymer content. Scaffolds with high POEGMEMA ratio (75%, w/w) show two times higher water uptake ratio (≈300%) and two times lower compression strength (19 kPa) compared to the ones with lower POEGMEMA content (50%, w/w). They also show desired degradation profiles in various aqueous solutions. While the scaffolds prepared with 25% and 50% PLGA are almost stable in first 20 days, they completely degrade in 40–50 days. Both scaffold formulations (25% PLGA-75% POEGMEMA and 50% PLGA-50% POEGMEMA) have similar proliferative properties for fibroblast cells. The scaffolds also do not show toxicity compared to control group according to live-dead assay.

Obtaining a polymer nanocomposite with optimum viscoelastic, thermal, and biocompatibility properties is the main objective when designing nanocomposite systems with potential applications in tissue engineering. For this purpose, a blend of Polycaprolactone (PCL) and Polyvinylidene fluoride (PVDF) in an 85/15 weight ratio, along with a nanocomposite reinforced by nanohydroxyapatite (nHA) particles, is fabricated using a solution casting method in a mold. The impact of nHA content on crystallinity, viscoelastic properties, thermal stability, and the properties–structure relationship of nanocomposites is evaluated using scanning electron microscopy (SEM). Dynamic mechanical thermal (DMTA) analysis is used to determine the William–Landel–Ferry (WLF) constants and the effect of nHA on the nanocomposite's viscoelastic behavior. The PCL/15PVDF/0.5 wt% nHA exhibits the maximum thermal stability (40% residual char value) and 95% increase in storage modulus at 90 °C (rubbery region) in comparison with PCL/15PVDF blend. Water contact angle (WCA) and biocompatibility tests are conducted on the PCL/15PVDF blend and nanocomposite scaffolds to design appropriate nanocomposite systems with potential applications in tissue engineering. The high hydrophilic properties are assigned to PCL/15PVDF/0.5 wt% nHA with a WCA of 67.5°. Finally, in vitro cell culture confirmed 0.5 wt% nHA significantly improves cell adhesion and cytotoxicity with MG-63 cells.

This study investigates the chemical–physical properties and anticorrosion effectiveness of UV-cured coatings produced using epoxidized vanillin (DGEVA) as biobased precursor, then reinforced by the addition of nanoclay. After optimizing the UV-curing parameters of three different formulations by Fourier transform infrared spectroscopy (FTIR), the thermo-mechanical properties of the coatings are assessed by differential scanning calorimetric analysis (DSC), dynamic thermal mechanical analysis (DTMA), and pencil hardness. The coatings are applied on mild steel substrates and then their barrier properties are investigated by electrochemical impedance spectroscopy measurements, immersing the samples in 3.5 wt% NaCl aerated solutions. The results show the good corrosion protective effectiveness of the biobased coatings. The nanoclay addition has a beneficial effect, as it hinders the diffusion of the aggressive ions from the electrolyte solution to the metal substrate. The reported findings demonstrate the possibility of using biobased precursors and UV-curing technology to reduce the environmental impact of the coating industry.

Sucrose and glycerol have gained attention as additives for hydrogels, owing to their capacity to exert considerable influence over the physicochemical, mechanical, and biological characteristics of these materials. Herein, these effects on agarose hydrogels (AHs) are explored. A series of AHs are synthesized using sucrose (30% and 300% w/v) and glycerol as additives. The storage modulus (10.0–13.7 kPa) and hydrophilicity of the hydrogels (contact angle < 50°) do not vary significantly with sucrose or glycerol addition. However, sucrose enhances the hydration capacity of the hydrogels by up to 170%, whereas glycerol reduces it. Interestingly, sucrose and glycerol individually do not have bacteriostatic effects against Staphylococcus epidermidis, but their combination significantly (p ≤ 0.001) inhibits the growth of both S. epidermidis and Pseudomonas aeruginosa by 63% and 29%, respectively, in comparison to native agarose. Cytotoxicity testing on NIH/3T3 murine fibroblasts reveals that sucrose increases cell viability up to 98%, while glycerol reduces it below 60%. Overall, these hydrogels hold promise for antibacterial biomedical applications as wound dressing materials and surface coatings for medical devices and can also be used to formulate bioinks for 3D bioprinting.

The significance of hydrogen energy has grown considerably due to climate change and the depletion of fossil fuels. PEM fuel cells are the key hydrogen technologies. Commercial membranes based on perfluorosulfonic acid (PFSA) with a polymer structure containing fluorine are currently available. However, it has been determined that certain perfluorosulfonic acids (PFSAs) are hazardous, persistent, and bioaccumulative. Advancements in hydrogen technology rely on effective, inexpensive, and perfluorocarbon-free membranes, specifically proton exchange membranes (PEMs). In this research, a PFSA-free polyacrylonitrile-co-methyl acrylate (PAN-MA) membrane doped with phosphoric acid is prepared using the electrospinning method and then characterized by SEM, FE-SEM, XRD, FTIR, TGA, DMA, and EIS. The DMA analysis reveals that the storage modulus of the doped membrane increases from 0.98 to 5.66 MPa at 80 °C. The nanofiber composite membrane, with a thickness of 181 µm, exhibits the highest proton conductivity of 0.306 S m⁻¹ at 20 °C, 1.76 times higher than that of the Nafion 212 membrane. The Nafion 212 membrane has an ionic conductivity of 0.173 S m⁻¹ under the same conditions. These results indicate that the prepared nanofiber membranes are promising materials for evaluating fuel cell applications.

Sustainable hybrid composites, made of two different natural plant fiber types, are increasingly being attracted by composite researchers, for their cost effectiveness and ability to control mechanical performances through varying weight ratios of different fibers. In contrast, their lower mechanical properties are reported in the literature, because of strength variations of different fiber types and an improper fiber-matrix stress distribution. Therefore, it is aimed to develop sustainable hybrid composites from two dry fiber preforms—woven fabric and short fiber preform—originated from same fiber type (jute). A highly packed short fiber preform is used as the core layer, while woven fabrics (plain/twill–rib/twill–diamond) are used in the skin layers for producing sandwiched hybrid jute composites. Mechanical tests and scanning electron microscopy images show that hybridized plain fabric/short fiber preform composites have better mechanical properties (≈58 MPa tensile strength/≈117 MPa flexural strength/≈112.12 kJm⁻² impact strength with an ≈487.4% improvement) compared to other fabric structures hybrid/nonhybrid composites. This enhancement is related to the interlocking of short fibers with long plain fabric leading to a strong fiber-matrix interfacial bonding. Thus, this developed hybrid composites, can be applied in many semi-structural applications, wherein composites’ low cost and mechanical performances are primary concerns.

Due to their ability to adapt to subtle changes in response to various external and internal stimuli, smart hydrogels have become increasingly popular in research and industry. However, many currently available hydrogels suffer from poor processability and inferior mechanical properties. For example, the preparation of a hydrogel network that can be subjected to melt processing and electrospinning is challenging. Herein, a series of mechanically strong, shape-memory hydrogels based on polyacrylic acid (PAAc) chains containing 20–50 mol% of crystallizable n-octadecylacrylate (C18A) segments are prepared by an organosolv method followed by in situ physical cross-linking via hydrophobic interactions. The hydrogels exhibit a reversible strong to weak gel transition at 50–60 °C and can be melt-processed at 60–100 °C, depending on the molar fraction of C18A. Additionally, the hydrogels can be dissolved in chloroform/ethanol mixture to form a viscous solution, which can then be used to produce a nanofibrous network by electrospinning. Effects of polymer concentration, volume ratio of solvents, and mole fraction of C18A on electrospinning are investigated to produce smooth, uniform nanofibers with small fiber diameter. The produced nanofibers, while maintaining their chemical structure, show significantly improved water adsorption capacity, enhanced mechanical properties, and fast shape-memory performance.

In recent years, the demand for filter media has increased dramatically, driven by the need to manufacture personal protective equipment and for various applications in the industrial and civil sectors. Nanofiber-based membranes are proposed as potential alternatives to commercial filtration devices. This study presents the design and implementation of an innovative pre-industrial electrospinning setup, combining a negatively charged spinneret and a positively charged counter-electrode, capable of producing polyvinylidene fluoride (PVDF) nanofibers with an average diameter of 410 nm and electrostatic surface potential values 3.7 times higher compared to a conventional electrospinning process, eliminating the need for further post-treatment. These properties are essential for improving mechanical and electrostatic filtration of small particles, including infectious droplets. The surface potential of the membranes is also long-lasting, as evidenced by tests one year after manufacture. As a case-study, these filters are used to manufacture surgical masks, reporting excellent performance in terms of bacterial filtration efficiency (BFE) up to 99.9%, and breathability (29.8±4.5 Pa cm⁻²) when compared to commercially available meltblown polypropylene (PP) face masks, and also complied with the stringent European standard (EN14683:2019) for type-II surgical masks. Furthermore, the pre-industrial setup allows for increased production capacity of up to 42 000 m² per year, suitable for large-scale production.

Isaac Newton once contemplated the fall of an apple, setting in motion a revolution in the understanding of gravity. In a similar spirit of curiosity and inquiry, here a journey is embarked upon to explore the intricate world of viscoelastic damping for polydimethylsiloxanes (PDMS). Inspired by the notion that even the simplest of phenomena can yield profound insights, a novel approach to study damping in silicone elastomers through a simple ball drop test is introduced. This novel solution allowes for precise measuring and analyzing the material's damping characteristics under various conditions. By carefully controlling the release and monitoring, the response of the falling ball by simple video tracking, valuable insights into the key viscoelastic properties of silicone blends are extracted, including rebound resilience, Young's modulus, and complex modulus. Through the analysis of trajectory data generated during the sphere's interaction with the silicone damper, dynamic and static material parameters are determined. Remarkably, these outcomes closely align with results obtained from cost-intensive and high-maintenance industrial measurement setups such as dynamic thermomechanical analysis (DTMA) or tensile testing. This approach not only simplifies the complexity of the system but also offers a cost-effective and efficient means of gaining essential knowledge in material science.

This study aims to develop gelatin methacryloyl (GelMA)-based symblepharon rings fortified with l-ascorbic acid (lAA), aiming for controlled release of vitamins for the treatment of the ocular surface, corneal healing, and acceleration of epithelial growth, while concurrently preventing potential inflammation. The human tears contain abundant IAA, which serves a protective role for ocular tissues. The utilization of 3D printing digital light processing technology not only navigating the manufacturing process of symblepharon rings, addressing challenges related to commercial production and expedited delivery to patients but also imparts enhanced flexibility compared to commercial products. This innovative approach also facilitates the production of rings that exhibit superior softness and are amenable to mechanical movements for ocular tissue engineering. The morphological, chemical, rheological, biological, thermal, and drug-release characteristics of 3D-printed lAA-loaded symblepharon rings are investigated. In the morphological characterization, it is observed that the rings exhibit a porous structure. In biocompatibility tests, Gelas and Gelas-low rings achieve over 75% viability. Following the cell test, scanning electron microscope images reveal fibroblasts adhering to Gelas and Gelas-low rings, spreading across their surfaces. Drug release studies conducted in phosphate-buffered saline at pH 7.4 reveal the complete release of lAA from Gelas-low within a 5-d incubation period.