Journal of Polymers and the Environment最新文献

Millimetre-sized core-shell hydrogel beads with dual-stimuli (pH and magnetic) sensitiveness were synthesized for drug release in cancer therapeutics. A facile synthesis approach was employed to fabricate gelatin/starch-g-oleic acid/alginate core-shell hydrogel beads HB1 and HB2 (with NiFe₂O₄ nanoparticles). Microscopic, HRSEM and EDS examinations verified the core-shell morphology of beads, while VSM measurements demonstrated magnetic responsiveness of HB2, with saturation magnetization of 1.89 emu/g. Swelling study in different pH environments ensured the pH-sensitivity of beads. The 5-FU encapsulation efficiency was found to be approximately 32% for both beads. At pH 7.4, the maximum drug release reached 76% for HB1 and 66% for HB2, while at pH 5.5, it was 54% for HB1 and 57% for HB2. The maximum drug release observed was 19% for 5-FU/HB1 and 21% for 5-FU/HB2 in pH 1.5. These results suggest the suitability of the beads for both oral delivery and direct tumour targeting system. Comparatively, hydrogel beads without NiFe₂O₄ NPs exhibited higher release over time than those containing NiFe₂O₄ NPs, attributed to increased core crosslinking density. At 300 min, 350 G magnetic field increased drug release of HB2 by 13%. The mechanism behind the drug release process was explained by Peppas-Sahlin kinetic, which showed that polymer relaxation dominates the drug release process with minimal contribution from Fickian diffusion. Moreover, cytotoxicity study using MCF-7 cells revealed that 5-FU loaded HB2 effectively induces cancer cell death, with an IC₅₀ of 7.7 µg/ml. Biocompatibility and hemocompatibility of the hydrogel systems were also demonstrated, thereby highlighting their promise for cancer therapeutics.

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Injectable stimuli-responsive hydrogels have emerged as a highly versatile class of biomaterials designed to enhance precision in drug delivery, tissue engineering, and regenerative medicine. These hydrogels are engineered to undergo controlled sol–gel transitions or degradation in response to specific environmental stimuli, including temperature, pH, enzymes, reactive oxygen species (ROS), glucose, light, ultrasound, magnetic fields, and electricity. By leveraging these stimuli-responsiveness properties, hydrogels offer significant advantages, such as improved biocompatibility, minimally invasive administration, and the ability to provide localized and sustained therapeutic effects. In this review, a comprehensive analysis of recent developments in injectable stimuli-responsive hydrogels is provided, with a focus on their classification, fabrication techniques, and biomedical applications. Particular attention is given to their role in cardiovascular therapy, cancer treatment, and other emerging fields where targeted therapeutic interventions are required. Furthermore, existing challenges related to hydrogel stability, responsiveness, and clinical translation are discussed, along with potential strategies for overcoming these limitations. By summarizing key advancements and addressing future perspectives, this review aims to provide a valuable resource for researchers working toward the next generation of smart hydrogel-based biomedical solutions.

Sustainable polyurethane materials derived from biomass or degradable components hold great promise. In this study, we polymerized UV-photoreactive curcumin (Cur), hydroxyethyl hexahydrotriazine (HT), and polyethylene glycol (PEG) with isophorone diisocyanate to craft a bio-based polyurethane (Cur-PU) film that exhibits both degradability and UV cross-linking capabilities. The feed ratio, encompassing NCO/OH and the hydroxyl groups of the raw materials, was meticulously optimized through a series of structural and physicochemical tests to yield high-performance, degradable Cur-PU films. FT-IR spectra confirmed the successful synthesis of the material. Property assessments revealed that adjusting the relevant ratios enhanced the structural rigidity and crosslinking density of the Cur-PU, leading to improved thermal stability, mechanical strength, and accelerated degradation time. Specifically, at an NCO/OH ratio of 1.6 and a PEG-OH/HT-OH/Cur-OH ratio of 2/4/4, the Cur-PU film exhibited balanced performance characteristics, including a tensile strength of 12.1 MPa, an elongation at break of 516%, a glass transition temperature of 90.7 °C, a 5% weight loss temperature of 230 °C, and a degradation time of 2.12 h in 2 M phosphoric acid/ethanol. Furthermore, the optimally prepared Cur-PU showcased exceptional recyclability and UV-photocrosslinking properties. Its recycled products retained PEG and Cur components, and the high UV-photocrosslinking content contributed to enhanced Young’s modulus and thermal properties. When compared to conventional PU materials, the PU material developed in this study demonstrates environmental friendliness and broader application potential, thanks to its recyclability and photosensitivity advantages.

In the past few years, the effective application of waterborne polyurethane (WPU) in the automotive industry, paint, packaging, and many other industries has drawn the attention of researchers to the synthesis of new WPU nanocomposite through structural modification and additive incorporation. In this research, layered double hydroxide (LDH) compounds were intercalated with glycine (Gly) to obtain the multifunctional nanoplates. The nanoplates were incorporated into the WPU matrix to create versatile antibacterial and oxygen barrier films while maintaining the essential characteristics of polyurethane films. The structure, mechanical performance, antibacterial activity, morphology, and water absorption behavior of the resulting nanocomposite films were thoroughly analyzed to assess their suitability for food packaging applications. The results show that LDH and LDH-Gly nanoplates improve the mechanical features of waterborne polyurethane-based films. Additionally, the modified films exhibited superior antibacterial activity compared to pure WPU films, showing increased resistance against both Gram-positive and Gram-negative bacteria. Furthermore, the incorporation of LDH-Gly nanoplates significantly reduced the water uptake and oxygen transmission rate (OTR), indicating improved barrier performance.

Poly(lactic acid)/poly(butylene adipate-co-terephthalate) (PLA/PBAT) blend foams containing 2, 4, and 6 phr chain extender (CE) were extruded at varying barrel and die temperatures (160, 175, and 190 °C). The correlations of the foams’ structural and physical properties with the rheological, molecular structure, and crystallization were investigated in depth. The analysis demonstrated that the foam with 2 phr CE extruded at 190 °C (FPPCE2T190) and the foam with 4 phr processed at 175 °C (FPPCE4T175) exhibited superior properties among the samples studied. Gel permeation chromatography revealed an enhancement in molecular weight for CE-containing foams, with the foam containing 4 phr CE prepared at 190 °C (FPPCE4T190) achieving a higher molecular weight than FPPCE4T175. Rheometric mechanical spectrometry identified that the FPPCE4T190 exhibited a highly branched structure with numerous short branches, while FPPCE4T175 featured fewer longer branches. Differential scanning calorimetry (DSC) further confirmed these findings, indicating that FPPCE4T190 achieved the highest degree of crystallinity. These results highlight the critical influence of CE content and processing temperature on the molecular structure and physical properties of the PLA/PBAT blend foams.

This study introduces a novel class of physically crosslinked hydrogels synthesized from high-molecular-weight copolymers consisting of itaconic acid (IA), methacrylic acid (MAA) and laponite RD, which efficiently removes cationic dyes. The copolymers synthesized via free-radical polymerization in a deep eutectic solvent demonstrated increased thermal stability with increasing MAA content. Rheological assessments revealed elastic solid behavior (G′ > G″), with decreased stiffness correlated with increased MAA content, which was attributed to diminished electrostatic interactions. Structural analyses, including WAXS/SAXS and TEM, confirmed the complete exfoliation of the clay and the formation of a hierarchical network; upon dye adsorption, an expansion of the basal spacing to 15–20 nm was observed. The hydrogels exhibited a swelling capacity of up to 38 g/g in pure water, which was reduced to 10 g/g in saline conditions. The highest adsorption capacity of basic fuchsin was determined to be 70 mg/g, achieving a 99.5% removal efficiency using 0.05 g/L of adsorbent over a 2-hour period. The adsorption process followed the Freundlich isotherm and was well described by a nonlinear pseudo-first-order (PFO) kinetic model. The dye adsorption process was spontaneous, and exothermic and followed physisorption. Crosslinking with calcium ions substantially increased the storage modulus by 252-fold and controlled the swelling ratio to 15.9 ± 0.7 g/g, facilitating regeneration cycles with 99.2 ± 0.2% efficiency. These findings position IA-MAA laponite RD hydrogels as sustainable materials with significant potential for application in dye-contaminated wastewater treatment.

In today’s world, the widespread utilization of plastics results in millions of tons of waste plastics being generated every year, which ultimately has become a great problem because of its environmental impact. Recycling of plastics can relieve this problem, as it prevents the loss of the material and energy used in their production and contributes to the reduction of CO₂ emissions. Depolymerization of plastic waste back to the original monomers seems to be the soundest alternative for plastics recycling, as it allows the production of the same original polymer or, eventually, the upcycling to other valuable chemicals. Polycaprolactone (PCL), one of the most widely used biodegradable polyesters, was subjected to enzymatic depolymerization to its monomer, 6-hydroxyhexanoic acid (6-HHA), catalyzed by a commercial Candida antarctica lipase B (CalB) following two alternative processes. The first one was carried out in aqueous medium and allowed the complete depolymerization of 100 g/L PCL in less than 24 h in an optimized phosphate-buffered medium. The second one is a novel two-phase system process in toluene/water emulsion, where PCL was initially dissolved in the organic phase and the hydrolysis product, 6-HHA, was accumulated in the buffered aqueous phase through the action of CalB. The highest depolymerizing activity among all the conditions tested, either in aqueous medium or in emulsion, was found in emulsion when the pH buffer was Tris-HCl, producing up to 71.2 g/L 6-HHA in only 5 h of enzyme treatment and achieving complete depolymerization of PCL in less than 24 h.

This study aimed to improve the dispersion of epoxy preoligomer (EPO) in a starch-based composite using a two-step blending process. EPO was prepared via the epoxy ring-opening reaction between epoxidized soybean oil and citric acid. Starch was plasticized in the first step to unfold its complex structure, followed by blending with EPO in the second step. The results showed that the two-step blending process improved tensile strength from 3.1 to 8.8 MPa and the elongation at break from 120.2 to 151.0% compared with the one-step blending mixing of starch and EPO. Fourier transform infrared microscopy confirmed the crosslinking reaction with well-dispersion of EPO in the composite matrix. Morphology analysis showed the compatibility between the starch and EPO phases was improved compared with the simultaneous blending process, which was also confirmed by analyzing the melting behavior through differential scanning calorimetry and dynamic mechanical analysis. The EPO content affects the final properties of the starch composite. The moisture content and water uptake decreased upon the addition of EPO. The present strategy offers a novel and simple blending process for the preparation of starch–EPO composites with superior characteristics.

Poly (butylene succinate) (PBS) is among the least studied biodegradable polyesters, where its high crystallinity and low extensibility had limited its wide- spread application for packaging. In this work, we designed a series of thermoplastic elastomers (TPEs) and vulcanizates (TPVs) based on PBS and ethylene vinyl acetate (EVA) with a focus on its modulus ((:E)) and elongation at break ((:{epsilon:}_{b})). The TPEs showed poor mechanical performance and using dicumyl peroxide (DCP), applied directly (D) and as a masterbatch with EVA (M), resulted in superior mechanical performance with the TPV based on the PBS: EVA composition of 90: 10-D showing the highest (:{epsilon:}_{b}) of 637.6% compared to the (:{epsilon:}_{b}) of 108.1% for PBS. The (:E) value of the TPV was 139.1 MPa compared to 353.2 MPa for PBS, which was due to the presence of EVA rubber. However, presence of 2% cellulose nanocrystal (CNC) increased (:E) to 225.9 MPa with the (:{epsilon:}_{b}) of 463%. Both PBS and the optimal TPVs showed high shape fixity even at 25°C due to its high crystallinity, while the TPVs and especially, the TPV- CNC (2.0%) showed higher recovery ratios caused by formation of an elastic 3D network of both the cured EVA droplets and CNCs.

Physically cross-linked hydrogels are typically prepared without the use of toxic chemicals. Owing to the reversible nature of their bonds, these hydrogels exhibit self-healing ability, fatigue resistance, and enhanced toughness, making them highly attractive for biomedical applications. However, their generally poor mechanical properties often limit their practical utility. To address these challenges, the fabrication of physically cross-linked hydrogels with superior mechanical performance through eco-friendly, facile, and cost-effective methods without employing any toxic chemicals is of considerable interest. In this study, fully physically cross-linked double-network hydrogels with ultra-high mechanical properties were successfully prepared using a simple and environmentally friendly approach. The hydrogels were based on poly (vinyl alcohol) (PVA), agar, and tannic acid (TA), without the use of any toxic reagents. Additionally, a silver nanocomposite hydrogel fabricated by immersing the prepared hydrogel in an aqueous solution of silver nitrate (AgNO₃). The optimized PVA/Agar/TA double-network hydrogel exhibited outstanding mechanical properties, including a high tensile strength of 9.66 MPa and a superior fracture toughness of 16.51 MJ/m³. These values further increased to 12 MPa and 19.5 MJ/m³, respectively, for the PVA/Agar/TA/Ag nanocomposite hydrogel. Moreover, due to the reversible multiple hydrogen bonds within the network structures, the hydrogels demonstrated excellent self-recovery behavior and remarkable anti-fatigue performance. The prepared hydrogels exhibited notable antioxidant activity and excellent biocompatibility. The incorporation of silver nanoparticles (Ag-nanoparticles) further enhanced their antibacterial properties. Moreover, the presence of Ag-nanoparticles imparted electrical conductivity to the corresponding hydrogel.Consequently, these multifunctional hydrogels are promising candidates for various biomedical applications.

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