Journal of Polymers and the Environment最新文献

Block copolymers, unlike reactive compatibilizers, can stably localize at the interface without reducing biodegradation rate, making them attractive compatibilizers for PLA/PBAT blends. For industrial use, they should be synthesized from commercial PBAT by melt polymerization to lower costs. However, melt polymerization is exposed to ambient moisture, leading to concurrent formation of PLA homopolymer. In this study, PLA–PBAT block copolymers were synthesized by both solution and melt polymerization with different lactide feed ratios. Melt polymerization was performed in an internal mixer as a precursor to reactive extrusion. Products were characterized by NMR, FT-IR, GPC, DSC, and TGA, and performance in blends was evaluated using DSC, SEM, and UTM. Melt samples displayed two cold crystallization peaks. The high-temperature peak corresponded to PLA homopolymer and became more pronounced with increasing lactide feed ratio. This suggests that excess lactide was consumed in homopolymerization. The presence of PLA homopolymer was more clearly observed in DTA than in GPC. In blends, melt samples improved tensile strength gradually with increasing lactide ratio, whereas solution samples showed the highest strength at a 1:1 PBAT-to-lactide ratio. At the ratio, the blend with solution samples exhibited higher tensile strength than that with melt samples. However, this difference was mitigated when melt samples with higher lactide ratios were incorporated at contents of 5 phr or less. The pristine blend formed metastable α′ crystals, while melt-sample-containing blends exhibited both α and α′ structures, with the α form becoming more dominant at higher lactide ratios.

Membrane technology is a promising solution for industrial wastewater treatment, though membrane fouling remains a major limitation. In this study, PVDF membranes were fabricated by incorporating 3-glycidoxypropyltrimethoxysilane (GPTMS)-modified cellulose (C-GPTMS) derived from oil palm empty fruit bunches (OPEFB) to enhance hydrophilicity and reduce fouling. C-GPTMS was synthesized via reflux and introduced into PVDF membranes via phase inversion. The resulting membranes exhibited increased water flux and significantly improved dye rejection up to 90% for methylene blue (MB) and 80% for reactive yellow (RY). Antifouling performance was also enhanced, with flux recovery ratios (FRR) reaching 99% for MB and 85% for RY. After five filtration cycles, the membranes retained over 80% of their initial flux, demonstrating excellent reusability for dye removal in wastewater treatment.

The hydrogel was synthesized via aqueous solution polymerization using carboxymethyl starch (CMS) as the base polysaccharide, ammonium persulfate (APS) as the initiator, N,N’-methylenebisacrylamide (MBA) as the crosslinker, and acrylamide (AAm) and acrylic acid (AAc) as the monomers. FTIR, XRD, FESEM, and TGA were used to characterize the synthesized hydrogel. Inhibitor concentration, crosslinker concentration, weight ratio of monomers, and weight ratio of CMS to total monomers were evaluated and optimized to affect swelling capacity. Hydrogel swelling behavior was investigated in relation to pH, time, temperature, and salinity of water. The samples exhibited the greatest swelling at pH 7 due to the carboxylate anions formed from their constituents. In distilled water at 25 °C, the sample prepared under optimized conditions absorbed 812.1 g/g of water. Increasing the temperature to 80 °C caused a 1050 g/g increase in swelling capacity. In addition, the hydrogel exhibited different swelling behavior in NaCl, MgCl₂, CaCl₂, FeCl₃, and AlCl₃ aqueous solutions, and its swelling ratio decreased with increasing cation valence. A Super Case II transport mechanism has also been demonstrated (diffusion exponent n ≥ 1.0), indicating that rapid water uptake is primarily driven by accelerated polymer chain relaxation.

Graphical Abstract

Recently, due to environmental concerns, research has been directed to develop water-based adhesives to replace chemically derived toxic, and non-biodegradable traditional adhesives. In the present study, the exopolysaccharide produced by Priestia aryabhattai KAG-18 (EPS/KAG-18) demonstrated adhesiveness, showing potential as an eco-friendly adhesive that can bind various surfaces, including wood, metal, and acrylic. The lap shear strength of the EPS/KAG-18 adhesive bonded teak wood to teak wood, pine wood to pine wood, metal-to-metal, and acrylic-to-acrylic exhibited 6.87 ± 0.68 MPa, 5.80 ± 0.96 MPa, 34.03 ± 1.37 MPa, 0.44 ± 0.09 MPa, respectively. At higher EPS/KAG-18 adhesive, teak wood to teak wood joints showed higher shear strength, compared to other specimens. A commercially available polyvinyl acetate (PVA) based adhesive exhibited lap shear strength of 7.87 ± 0.54 MPa for teak wood, 6.83 ± 1.57 MPa for pine wood, 6.05 ± 2.71 MPa for metal, and 0.70 ± 0.25 MPa for acrylic. Thermal stability tests using TGA and DSC analyses revealed that the EPS/KAG-18 adhesive remained stable up to 250 °C without the presence of a glass transition. FT-IR spectroscopy indicated the presence of hydroxyl and carboxyl groups in EPS/KAG-18 characteristics of polysaccharides. Contact angle measurements indicated a hydrophilic nature on wood and metal surfaces (< 90°) and hydrophobic characteristics on acrylic substrates (> 90°). EPS/KAG-18 (3.0 to 9.0% w/v) solutions showed shear-thinning rheology, G’ > G”, and best fit to the Herschel–Bulkley model applicable for fluids with yield stress. Finite element analysis (FEA) of the EPS/KAG-18 bonded single lap joint of acrylic specimens revealed that the stress was concentrated at the edges of the joint, while minimal stress was observed in the central region. Hence, in the present study, we report for the first time the modelling of rheological behaviour and FEA of adhesive joints along with its adhesive properties.

Chitosan/polyvinylpyrrolidone (CH/PVP) scaffolds incorporating varying concentrations of dicalcium silicate (CS) particles − 0, 5, and 15 wt% (the corresponding codes CS0/CH: PVP, CS5/CH: PVP, and CS15/CH: PVP, respectively) - were fabricated using the freeze-drying technique to control their physicochemical properties, biocompatibility, drug release profile, and antimicrobial activity. Different analytical techniques were used, such as Transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) to determine structural and compositional characteristics of either ceramic powder or scaffolds. In vitro bioactivity and biodegradation were evaluated using simulated body fluid (SBF) maintained at 37 °C. Scanning electron microscopy (SEM) images indicated extensive apatite formation on the CS15/CH: PVP scaffold, forming a dense mineralized layer on its surface. The impact of incorporating CS on drug release behavior was examined using gentamicin as a model antibiotic agent. Results showed that increasing CS content led to a significant decrease in the drug release rate, suggesting a sustained release profile. Cytotoxicity tests using the human fibroblast cell line BJ1 demonstrated that all scaffold formulations exhibited minimal toxicity and were comparable to the negative control. The antimicrobial effectiveness was tested against Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Salmonella typhi, and Candida albicans, demonstrating the scaffolds’ broad-spectrum antibacterial and antifungal capabilities. Overall, the CS/CH: PVP scaffolds presented a multifunctional platform with potential for bone tissue regeneration and localized antibiotic delivery.

The increasing demand for efficient water purification technologies has accelerated the development of advanced adsorbents for dye removal. In this study, a novel high-performance adsorbent was synthesized by grafting 2,5-dimercapto-1,3,4-thiadiazole (DMTD) onto a chitosan (CS)–glutaraldehyde–trimesic acid (TMA) framework (CS@TMA@DMTD) through a straightforward two-step process. Comprehensive physicochemical characterization, including Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area analysis, and X-Ray Photoelectron Spectroscopy (XPS), confirmed the successful incorporation of functional thiol (–SH) and carboxyl (–COOH) groups, which synergistically enhance the adsorption performance of the composite. The adsorption capacity of pristine crosslinked chitosan was evaluated at 96.3 mg/g, while the modified CS@TMA@DMTD composite exhibited a significantly enhanced capacity of 218.4 mg/g and achieved 96.5% removal under optimal conditions (298 K, pH 8, initial MB concentration 25 mg/L, and contact time 60 min), demonstrating the effectiveness of the functional modifications. Batch adsorption studies demonstrated a strong pH dependence, with optimal performance under neutral to slightly alkaline conditions. Kinetic data were best described by the pseudo-first-order model, suggesting that physical adsorption dominates the process. In contrast, the equilibrium data were fitted to the Langmuir isotherm model, indicating monolayer coverage on a homogeneous surface. Thermodynamic parameters (ΔG° < 0, ΔH° < 0) confirmed that the adsorption process is spontaneous and exothermic. Reusability tests demonstrated the stability and efficiency of CS@TMA@DMTD over five cycles, with only a ~ 5% performance loss. Its high capacity, fast kinetics, and recyclability make it a promising eco-friendly adsorbent for dye-contaminated wastewater, surpassing many conventional chitosan-based materials.

Poly(lactic acid) (PLA) is a promising biopolymer valued for its degradability and versatility. Conventional ring-opening polymerization (ROP) methods, which involve multistep processes under high temperature and vacuum conditions, often require high energy input and prolonged reaction times. In this study, ultrasonic-assisted ROP was first optimized using the conventional metal catalyst stannous octoate (Sn(Oct)₂) to evaluate the effects of ultrasonic power and reaction time. The optimal conditions (99.29 W, 3.66 h) produced PLA with a molecular weight of 88.18 kg/mol, 44.76% crystallinity, and a melting temperature of 165.64 °C, while reducing energy consumption by 49.98% compared to the conventional thermal process. Following this optimization, creatinine was employed as a metal-free biocatalyst to explore a greener catalytic alternative. In addition, methanol was introduced as a co-initiator at different ratios (0%, 0.5%, 1%, and 1.5%). The presence of methanol, particularly at 1.5%, enhanced chain initiation and propagation, leading to higher molecular weight and improved physical and thermal properties of PLA synthesized with creatinine. These findings suggest that the combined use of ultrasonic irradiation, biocatalyst, and co-initiator provides a potential pathway toward more energy-efficient and sustainable PLA production.

This research focuses on creating an innovative pH-sensitive nanocarrier for targeted paclitaxel delivery to breast cancer cells. The nanocarrier, consisting of hyaluronic acid grafted poly (acrylic acid-co-allyl glycidyl ether) conjugated mesoporous magnetic graphene quantum dots, is engineered to release the drug specifically in the acidic tumor environment. The study examined key factors affecting paclitaxel measurement. The Langmuir model provided the best fit, with a maximum sorption capacity of 15.851 mg g⁻¹. Kinetic modeling aligned well with the pseudo-second order kinetic model, supporting physisorption in the adsorption process, facilitated by a high density of active sites. Thermodynamic analysis revealed that drug adsorption onto nanocomposite was endothermic and spontaneous. The drug-loaded nanocomposite exhibited limited release in simulated physiological conditions (pH 7.4, 37 °C), but increased release in tumor tissue conditions (pH 5.6, 37 °C), enabling sustained drug release at the target site. The zero-order kinetic model best described drug release from the nanocarrier at pH 5.6, indicating non-Fickian diffusion transport control. The cytotoxicity results demonstrated that the nanocarrier was more toxic to MCF-7 cells than nanocomposite without the drug. Based on the collected data, the developed nanocarrier with appropriate pH-responsiveness shows significant potential as an anticancer agent.

The use of synthetic scaffolds as an alternative strategy for repairing bone defects has garnered significant attention in bone tissue engineering. Human mesenchymal stem cells (MSCs) play a crucial role in the body’s regeneration processes, making the identification of suitable inducers for treating osteogenesis disorders essential. This study is the first report in the world on the induction of differentiation of human adipose-derived mesenchymal stem cells (hAD-MSCs) into osteoblast-like cells on an innovative scaffold of carboxymethylcellulose, polyglycerol, and sebacic acid, containing vitamin D2 and chondroitin-4 sulfate. Initially, the scaffolds were created using molding and salt washing techniques. Their morphology, structure, and mechanical characteristics were examined through techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), Thermogravimetric Analysis (TGA), and Fourier-transform infrared spectroscopy (FTIR). The optimal concentrations of vitamin D2 and chondroitin sulfate (CS) in the differentiation medium and scaffold structure were determined using the MTT assay. Viability and morphology were assessed through acridine orange-ethidium bromide (AO/EB) staining. Differentiation experiments were conducted with various concentrations of inducers both in the medium and on the scaffolds. Cell differentiation into osteoblasts was quantified through alkaline phosphatase (ALP) enzyme activity assays and calcium content deposition (C.C). Qualitative assessments included staining the mineralized matrix with Alizarin Red and Kossa staining. Finally, the expression of bone marker genes, including RUNX-2, collagen I, osteocalcin, osteonectin, and ALP, was quantitatively evaluated using Real-Time PCR. The results of the osteogenic differentiation experiments demonstrated that scaffolds containing vitamin D2 and chondroitin-4-sulfate effectively induced osteogenic differentiation in mesenchymal stem cells. These scaffolds significantly increased alkaline phosphatase (ALP) activity and calcium deposition, as confirmed by specialized staining methods such as Alizarin Red and von Kossa. Furthermore, the expression levels of key genes involved in osteogenic differentiation were significantly upregulated, confirming the efficacy of these scaffolds in promoting osteogenesis.

Developing an affordable, stable, and efficient photocatalyst is essential for addressing environmental pollution. In this study, A Sulfur-doped Zinc oxide(S@ZnO) and sulfur-doped Zinc oxide/Chitosan (S@ZnO/Chitosan) composites with enhanced photocatalytic capabilities for degrading tetracycline under visible light was synthesized. The synthesized composites were characterized using techniques such as X-ray diffraction (XRD), Field-Emission Scanning Electron Microscopy (FESEM), and energy-dispersive X-ray spectroscopy (EDX) to confirm their structure and composition. The photocatalytic activity was assessed by measuring tetracycline degradation under visible. Machine learning (Random Forest regression) is employed to model and predict degradation efficiency. It evaluated by a 10 fold cross-validation, and the results clearly show that an average R² of 0.978 and a relatively low average MSE of 15.334 across the 10 folds, indicating strong predictive performance and accuracy. Importance of individual features (TC concentration, pH, dosage, and time) and their products are evaluated using Random Forest Average Feature Importance (Gini) and SHAP(SHapley Additive exPlanations) Global Feature. Our findings reveal that the S@ZnO/Chitosan nanocomposite achieved a 95% degradation rate of tetracycline in 120 min, compared to 50% degradation using S@ZnO alone. Kinetic modeling confirmed pseudo-first-order behavior, with rate constant for the chitosan composite was 0.016 min⁻¹, significantly higher than 0.005 min⁻¹ for S@ZnO. These results demonstrate that incorporating chitosan into S@ZnO. substantially enhances photocatalytic efficiency by improving electron-hole pair separation and increasing the lifetime of photogenerated charges. This innovative S@ZnO. /chitosan nanocomposite shows significant potential for practical applications in environmental remediation.