Thermo-mechanical, antimicrobial and biocompatible properties of PVC blends based on imidazolium ionic liquids

An in-situ dissolving-co-crosslinking strategy for fabricating high-strength, wet-stable, and biocompatible multiscale cellulosic paper-based plastics

Developing degradable plastics with excellent mechanical strength and wet stability from renewable and biodegradable biomass resources remains challenging. Here, we propose a simple one-step strategy for the in-situ multiscale dissolution of cellulose and crosslinking with 1,4-butanediol diglycidyl ether (BDDE) within a mixture of BDDE and AlCl3/ZnCl2 aqueous solution at room temperature. This strategy enables the synthesis of cellulosic paper-based bioplastics with high mechanical strength and wet stability from cellulose paper. In this process, conventional cellulose paper is partially dissolved, and simultaneously, BDDE forms chemical crosslinking with undissolved micro-level, nano-level cellulose fibers and dissolved cellulose macromolecules through an autocatalytic effect from AlCl3/ZnCl2 aqueous solution, resulting in multiscale physicochemical entanglements and multiple hydrogen bonds. Hence, the prepared bioplastic's dry and wet strength reached 58.2 MPa and 24.2 MPa, respectively, about 6.9 times and 71.2 times higher than untreated paper-based materials. The prepared bioplastic showed excellent wet stability, biosafety, and biodegradability. The density functional theory (DFT) simulation data indicates that Al3+, Zn2+ ions, and freely hydrated hydrogen protons are crucial to the dissolving-co-crosslinking system. This strategy involves only green and recyclable chemicals, offering a promising pathway for producing strong and biodegradable cellulosic paper-based bioplastics as an alternative to nondegradable plastics.

Synthesis, Characterisation, and In Vitro Evaluation of Biocompatibility, Antibacterial and Antitumor Activity of Imidazolium Ionic Liquids

In recent decades, ionic liquids (ILs) have garnered research interest for their noteworthy properties, such as thermal stability, low or no flammability, and negligible vapour pressure. Moreover, their tunability offers limitless opportunities to design ILs with properties suitable for applications in many industrial fields. This study aims to synthetise two series of methylimidazolium ILs bearing long alkyl chain in their cations (C9, C10, C12, C14, C16, C18, C20) and with tetrafluoroborate (BF4) and the 1,3-dimethyl-5-sulfoisophthalate (DMSIP) as counter ions. The ILs were characterised using 1H-NMR and MALDI-TOF, and their thermal behaviour was investigated through DSC and TGA. Additionally, the antimicrobial, anticancer, and cytotoxic activities of the ILs were analysed. Moreover, the most promising ILs were incorporated at different concentrations (0.5, 1, 5 wt%) into polyvinyl chloride (PVC) by solvent casting to obtain antimicrobial blend films. The thermal properties and stability of the resulting PVC/IL films, along with their hydrophobicity/hydrophilicity, IL surface distribution, and release, were studied using DSC and TGA, contact angle (CA), SEM, and UV-vis spectrometry, respectively. Furthermore, the antimicrobial and cytotoxic properties of blends were analysed. The in vitro results demonstrated that the antimicrobial and antitumor activities of pure ILs against t Listeria monocytogenes, Escherichia coli, Pseudomonas fluorescens strains, and the breast cancer cell line (MCF7), respectively, were mainly dependent on their structure. These activities were higher in the series containing the BF4 anion and increased with the increase in the methylimidazolium cation alkyl chain length. However, the elongation of the alkyl chain beyond C16 induced a decrease in antimicrobial activity, indicating a cut-off effect. A similar trend was also observed in terms of in vitro biocompatibility. The loading of both the series of ILs into the PVC matrix did not affect the thermal stability of PVC blend films. However, their Tonset decreased with increased IL concentration and alkyl chain length. Similarly, both the series of PVC/IL films became more hydrophilic with increasing IL concentration and alkyl chain. The loading of ILs at 5% concentration led to considerable IL accumulation on the blend film surfaces (as observed in SEM images) and, subsequently, their higher release. The biocompatibility assessment with healthy human dermal fibroblast (HDF) cells and the investigation of antitumoral properties unveiled promising pharmacological characteristics. These findings provide strong support for the potential utilisation of ILs in biomedical applications, especially in the context of cancer therapy and as antibacterial agents to address the challenge of antibiotic resistance. Furthermore, the unique properties of the PVC/IL films make them versatile materials for advancing healthcare technologies, from drug delivery to tissue engineering and antimicrobial coatings to diagnostic devices.

Molecularly Mixed Composite Membranes for Gas Separation Based on Macrocycles Embedded in a Polyimide

Polyimides are a polymer class that has been extensively investigated as a membrane material for gas separation owing to its interesting permselective properties in a wide range of operation temperatures and pressures. In order to improve their properties, the addition of different filler types is currently studied. p-tert-Butylcalix[n]arene macrocycles (PTBCs) with different cavity sizes (PTBC4, PTBC6, PTBC8) were used as fillers in a commercial thermoplastic polyimide, with a concentration in the range 1-9 wt%, to develop nanocomposite membranes for gas separation. The selected macrocycles are attractive organic compounds owing to their porous structure and affinity with organic polymers. The nanocomposite membranes were prepared in the form of films in which the polymeric matrix is a continuous phase incorporating the dispersed additives. The preparation was carried out according to a pre-mixing approach in a mutual solvent, and the solution casting was followed by a controlled solvent evaporation. The films were characterized by investigating their miscibility, morphology, thermal and spectral properties. The gas transport through these films was examined as a function of the temperature and also time. The results evidenced that the incorporation of the chosen nanoporous fillers can be exploited to enhance molecular transport, offering additional pathways and promoting rearrangements of the polymeric chains.

Polyurethanes Modified by Ionic Liquids and Their Applications

Polyurethane (PU) refers to the polymer containing carbamate groups in its molecular structure, generally obtained by the reaction of isocyanate and alcohol. Because of its flexible formulation, diverse product forms, and excellent performance, it has been widely used in mechanical engineering, electronic equipment, biomedical applications, etc. Through physical or chemical methods, ionic groups are introduced into PU, which gives PU electrical conductivity, flame-retardant, and antistatic properties, thus expanding the application fields of PU, especially in flexible devices such as sensors, actuators, and functional membranes for batteries and gas absorption. In this review, we firstly introduced the characteristics of PU in chemical and microphase structures and their related physical and chemical performance. To improve the performance of PU, ionic liquids (ILs) were applied in the processing or synthesis of PU, resulting in a new type of PU called ionic PU. In the following part of this review, we mainly summarized the fabrication methods of IL-modified PUs via physical blending and the chemical copolymerization method. Then, we summarized the research progress of the applications for IL-modified PUs in different fields, including sensors, actuators, transistors, antistatic films, etc. Finally, we discussed the future development trends and challenges faced by IL-modified PUs.

Degradation of polyvinyl chloride by a bacterial consortium enriched from the gut of Tenebrio molitor larvae

Polyvinyl chloride (PVC), a carbon backbone synthetic plastic containing chlorine element, is one of six widely used plastics accounting for 10% global plastics production. PVC wastes are recalcitrant to be broken down in the environment but release harmful chlorinated compounds, causing damage to the ecosystem. Although biodegradation represents a sustainable approach for PVC reduction, virtually no efficient bacterial degraders for additive-free PVC have been reported. In addition, PVC depolymerization by Tenebrio molitor larvae was suggested to be gut microbe-dependent, but to date no additive-free PVC degraders have been isolated from insect guts. In this study, a bacterial consortium designated EF1 was newly enriched from the gut of Tenebrio molitor larvae, which was capable of utilizing additive-free PVC for its growth with the PVC-mass reduction and dechlorination of PVC. PVC films inoculated with consortium EF1 for 30 d were analyzed by diverse polymer characterization methods including atomic force microscopy, scanning electron microscope, water contact angle, time-of-flight secondary ion mass spectrometry, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis technique, and ion chromatography. It was found that bio-treated PVC films were covered with tight biofilms with increased -OH and -CC- groups and decreased chlorine contents, and erosions and cracks were present on their surfaces. Meanwhile, the hydrophilicity of bio-treated films increased, but their thermal stability declined. Furthermore, M_w, M_n and M_z values were reduced by 17.0%, 28.5% and 16.1% using gel permeation chromatography, respectively. In addition, three medium-chain aliphatic primary alcohols and their corresponding fatty acids were identified as PVC degradation intermediates by gas chromatography-mass spectrometry. Combing all above results, it is clear that consortium EF1 is capable of efficiently degrading PVC polymer, providing a unique example for PVC degradation by gut microbiota of insects and a feasibility for the removal of PVC wastes.

Temperature Responsive Copolymers Films of Polyether and Bio-Based Polyamide Loaded with Imidazolium Ionic Liquids for Smart Packaging Applications

Temperature-responsive materials are highly interesting for temperature-triggered applications such as drug delivery and smart packaging. Imidazolium Ionic Liquids (ILs), with a long side chain on the cation and a melting temperature of around 50 °C, were synthetized and loaded at moderate amounts (up to 20 wt%) within copolymers of polyether and a bio-based polyamide via solution casting. The resulting films were analyzed to assess their structural and thermal properties, and the gas permeation changes due to their temperature-responsive behavior. The splitting of FT-IR signals is evident, and, in the thermal analysis, a shift in the glass transition temperature (Tg) for the soft block in the host matrix towards higher values upon the addition of both ILs is also observed. The composite films show a temperature-dependent permeation with a step change corresponding to the solid-liquid phase change in the ILs. Thus, the prepared polymer gel/ILs composite membranes provide the possibility of modulating the transport properties of the polymer matrix simply by playing with temperature. The permeation of all the investigated gases obeys an Arrhenius-type law. A specific permeation behavior, depending on the heating-cooling cycle sequence, can be observed for carbon dioxide. The obtained results indicate the potential interest of the developed nanocomposites as CO₂ valves for smart packaging applications.

Polymer Blends Based on 1-Hexadecyl-3-methyl Imidazolium 1,3-Dimethyl 5-Sulfoisophthalate Ionic Liquid: Thermo-Mechanical, Surface Morphology and Antibacterial Properties

In this study, antibacterial polymer blends based on Polyvinyl Chloride (PVC) and Polystyrene-Ethylene-Butylene-Styrene (SEBS), loaded with the ionic liquid (IL) 1-hexadecyl-3-methyl imidazolium 1,3-dimethyl 5-sulfoisophthalate (HdmimDMSIP) at three different concentrations (1%, 5%, and 10%), were produced. The IL/blends were characterized by their thermo-mechanical properties, surface morphology, and wettability. IL release from the blends was also evaluated. The agar diffusion method was used to test the antibacterial activity of the blends against Staphylococcus epidermidis and Escherichia coli. Results from thermal analyses showed compatibility between the IL and the PVC matrix, while phase separation in the SEBS/IL blends was observed. These results were confirmed using PY-GC MS data. SEM analyses highlighted abundant IL deposition on PVC blend film surfaces containing the IL at 5-10% concentrations, whereas the SEBS blend film surfaces showed irregular structures similar to islands of different sizes. Data on water contact angle proved that the loading of the IL into both polymer matrices induced higher wettability of the blends' surfaces, mostly in the SEBS films. The mechanical analyses evidenced a lowering of Young's Modulus, Tensile Stress, and Strain at Break in the SEBS blends, according to IL concentration. The PVC/IL blends showed a similar trend, but with an increase in the Strain at Break as IL concentration in the blends increased. Both PVC/IL and SEBS/IL blends displayed the best performance against Staphylococcus epidermidis, being active at low concentration (1%), whereas the antimicrobial activity against Escherichia coli was lower than that of S. epidermidis. Release data highlighted an IL dose-dependent release. These results are promising for a versatile use of these antimicrobial polymers in a variety of fields.

Ionic Liquids: Emerging Antimicrobial Agents

Antimicrobial resistance has become a serious threat to global health. New antimicrobials are thus urgently needed. Ionic liquids (ILs), salts consisting of organic cations and anions with melting points less than 100°C, have been recently found to be promising in antimicrobial field as they may disrupt the bacterial wall and membrane and consequently lead to cell leakage and death. Different types of antimicrobial ILs are introduced in the review, including cationic, polymeric, and anionic ILs. Being the main type of the antimicrobial ILs, the review focuses on the structure and the antimicrobial mechanisms of cationic ILs. The quantitative structure-activity relationship (QSAR) models of the cationic ILs are also included. Increase in alkyl chain length and lipophilicity is beneficial to increase the antimicrobial effects of cationic ILs. Polymeric ILs are homopolymers of monomer ILs or copolymers of ILs and other monomers. They have great potential in the field of antibiotics as they provide stronger antimicrobial effects than the sum of the monomer ILs. Anionic ILs are composed of existing anionic antibiotics and organic cations, being capable to enhance the solubility and bioavailability of the original form. Nonetheless, the medical application of antimicrobial ILs is limited by the toxicity. The structural optimization aided by QSAR model and combination with existing antibiotics may provide a solution to this problem and expand the application range of ILs in antimicrobial field.