Self-healing polymer nanocomposite materials: A review

On-demand bactericidal and self-adaptive antifouling hydrogels for self-healing and lubricant coatings of catheters

Catheter-related infections are one of the most common nosocomial infections with increasing morbidity and mortality, and robust antibacterial or antifouling catheter coatings remain great challenges for long-term implantation. Herein, multifunctional hydrogel coatings were developed to provide persistent and self-adaptive antifouling and antibacterial effects with self-healing and lubricant capabilities. Polyvinyl alcohol (PVA) with β-cyclodextrin (β-CD) grafts (PVA-Cd) and 4-arm polyethylene glycol (PEG) with adamantane and quaternary ammonium compound (QAC) terminals (QA-PEG-Ad) were crosslinked through host-guest recognitions between adamantane and β-CD moieties to acquire PVEQ coatings. In response to bacterial infections, QACs exhibit reversible transformation between zwitterions (pH 7.4) and cationic lactones (pH 5.5) to generate on-demand bactericidal effect. Highly hydrophilic PEG/PVA backbones and zwitterionic QACs build a lubricate surface and decrease the friction coefficient 10 times compared with that of bare catheters. The antifouling hydrated layer significantly inhibits blood protein adsorption and platelet activation and reveals negligible hemolysis and cytotoxicity. The dynamic host-guest crosslinking achieves full self-healing of cracks in PVEQ hydrogels, and the mechanical profiles were recovered to over 90 % after rejuvenating the broken hydrogels, exhibiting a long-term stability after mechanical stretching, twisting, knotting and compression. After subcutaneous implantation and local bacterial infection, the retrieved PVEQ-coated catheters display no tissue adhesion and 3 log folds lower bacterial number than that of bare catheters. PVEQ coatings effectively prevent the repeated bacterial infections and there are few inflammatory reactions in the surrounding tissue, while substantial lymphoid infiltration and inflammatory cell aggregation occur in muscle tissues around the bare catheter. Thus, this study demonstrates a catheter coating strategy by on-demand bactericidal, self-adaptive antifouling, self-healing and lubricant hydrogels to address medical devices-related infections. STATEMENT OF SIGNIFICANCE: It is estimated over two billion peripheral intravenous catheters are annually used in hospitals around the world, and catheter-associated infection has become a great clinical challenge with rapidly rising morbidity and mortality. Surface coating is considered a promising approach, but substantial challenges remain in the development of coatings that simultaneously satisfy both anti-fouling and antibacterial attributes. Even more, few attempts have been made to design mechanically robust coatings and reversible antibacterial or antifouling capabilities, which are critical for long-term medical implants. To address these challenges, we propose a concise strategy to develop hydrogel coatings from commercially available poly(ethylene glycol) and polyvinyl alcohol. In addition to self-healing and lubricant capabilities, the reversible conversion between zwitterionic and cationic lactones of quaternary ammonium compounds enables on-demand bactericidal and self-adaptive antifouling effects.

Nanoindentation Response of Structural Self-Healing Epoxy Resin: A Hybrid Experimental-Simulation Approach

In recent years, self-healing polymers have emerged as a topic of considerable interest owing to their capability to partially restore material properties and thereby extend the product's lifespan. The main purpose of this study is to investigate the nanoindentation response in terms of hardness, reduced modulus, contact depth, and coefficient of friction of a self-healing resin developed for use in aeronautical and aerospace contexts. To achieve this, the bifunctional epoxy precursor underwent tailored functionalization to improve its toughness, facilitating effective compatibilization with a rubber phase dispersed within the host epoxy resin. This approach aimed to highlight the significant impact of the quantity and distribution of rubber domains within the resin on enhancing its mechanical properties. The main results are that pure resin (EP sample) exhibits a higher hardness (about 36.7% more) and reduced modulus (about 7% more), consequently leading to a lower contact depth and coefficient of friction (11.4% less) compared to other formulations that, conversely, are well-suited for preserving damage from mechanical stresses due to their capabilities in absorbing mechanical energy. Furthermore, finite element method (FEM) simulations of the nanoindentation process were conducted. The numerical results were meticulously compared with experimental data, demonstrating good agreement. The simulation study confirms that the EP sample with higher hardness and reduced modulus shows less penetration depth under the same applied load with respect to the other analyzed samples. Values of 877 nm (close to the experimental result of 876.1 nm) and 1010 nm (close to the experimental result of 1008.8 nm) were calculated for EP and the toughened self-healing sample (EP-R-160-T), respectively. The numerical results of the hardness provide a value of 0.42 GPa and 0.32 GPa for EP and EP-R-160-T, respectively, which match the experimental data of 0.41 GPa and 0.30 GPa. This validation of the FEM model underscores its efficacy in predicting the mechanical behavior of nanocomposite materials under nanoindentation. The proposed investigation aims to contribute knowledge and optimization tips about self-healing resins.

Advances in Materials with Self-Healing Properties: A Brief Review

The development of materials with self-healing capabilities has garnered considerable attention due to their potential to enhance the durability and longevity of various engineering and structural applications. In this review, we provide an overview of recent advances in materials with self-healing properties, encompassing polymers, ceramics, metals, and composites. We outline future research directions and potential applications of self-healing materials (SHMs) in diverse fields. This review aims to provide insights into the current state-of-the-art in SHM research and guide future efforts towards the development of innovative and sustainable materials with enhanced self-repair capabilities. Each material type showcases unique self-repair mechanisms tailored to address specific challenges. Furthermore, this review investigates crack healing processes, shedding light on the latest developments in this critical aspect of self-healing materials. Through an extensive exploration of these topics, this review aims to provide a comprehensive understanding of the current landscape and future directions in self-healing materials research.

3D Printing of Self-Healing Materials

This review article presents a comprehensive overview of the latest advances in the field of 3D printable structures with self-healing properties. Three-dimensional printing (3DP) is a versatile technology that enables the rapid manufacturing of complex geometric structures with precision and functionality not previously attainable. However, the application of 3DP technology is still limited by the availability of materials with customizable properties specifically designed for additive manufacturing. The addition of self-healing properties within 3D printed objects is of high interest as it can improve the performance and lifespan of structural components, and even enable the mimicking of living tissues for biomedical applications, such as organs printing. The review will discuss and analyze the most relevant results reported in recent years in the development of self-healing polymeric materials that can be processed via 3D printing. After introducing the chemical and physical self-healing mechanism that can be exploited, the literature review here reported will focus in particular on printability and repairing performances. At last, actual perspective and possible development field will be critically discussed.

Next-Generation Vitrimers Design through Theoretical Understanding and Computational Simulations

Vitrimers are an innovative class of polymers that boast a remarkable fusion of mechanical and dynamic features, complemented by the added benefit of end-of-life recyclability. This extraordinary blend of properties makes them highly attractive for a variety of applications, such as the automotive sector, soft robotics, and the aerospace industry. At their core, vitrimer materials consist of crosslinked covalent networks that have the ability to dynamically reorganize in response to external factors, including temperature changes, pressure variations, or shifts in pH levels. In this review, the aim is to delve into the latest advancements in the theoretical understanding and computational design of vitrimers. The review begins by offering an overview of the fundamental principles that underlie the behavior of these materials, encompassing their structures, dynamic behavior, and reaction mechanisms. Subsequently, recent progress in the computational design of vitrimers is explored, with a focus on the employment of molecular dynamics (MD)/Monte Carlo (MC) simulations and density functional theory (DFT) calculations. Last, the existing challenges and prospective directions for this field are critically analyzed, emphasizing the necessity for additional theoretical and computational advancements, coupled with experimental validation.

Self-healing polymers for surface scratch regeneration

Recently, there has been a significant increase in academic and industrial interest in self-healing polymers (SHPs) due to their remarkable ability to regenerate scratched surfaces and materials of astronomical significance. Scientists have been inspired by the magical repairing mechanism of the living world. They transformed the fiction of self-healing into reality by designing engrossing polymeric materials that could self-repair mechanical abrasions repeatedly. As a result, the durability of the materials is remarkably improved. Thus, the idea of studying SHPs passively upholds economic and environmental sustainability. However, the critical areas of self-healing (including healing efficiency, healing mechanism, and thermo-mechanical property changes during healing) are under continuous scientific improvisation. This review highlights recent notable advances of SHPs for application in regenerating scratched surfaces with various distinctive underlying mechanisms. The primary focus of the work is aimed at discussing the impact of SHPs on scratch-healing technology. Beyond that, insights regarding scratch testing, methods of investigating polymer surfaces, wound depths, the addition of healing fillers, and the environmental conditions maintained during the healing process are reviewed thoroughly. Finally, broader future perspectives on the challenges and prospects of SHPs in healing surface scratches are discussed.

Highly Self-Healable Polymeric Coating Materials Based on Charge Transfer Complex Interactions with Outstanding Weatherability

In this study, we prepare highly self-healable polymeric coating materials using charge transfer complex (CTC) interactions. The resulting coating materials demonstrate outstanding thermal stability (1 wt% loss thermal decomposition temperature at 420 °C), rapid self-healing kinetics (in 5 min), and high self-healing efficiency (over 99%), which is facilitated by CTC-induced multiple interactions between the polymeric chains. In addition, these materials exhibit excellent optical properties, including transmittance over 91% and yellow index (YI) below 2, and show enhanced weatherability with a ΔYI value below 0.5 after exposure to UV light for 72 h. Furthermore, the self-healable coating materials developed in this study show outstanding mechanical properties by overcoming the limitations of conventional self-healing materials.

Combing experimental methods and molecular simulations to study self-healing behaviors of polyurethane elastomers containing multiple hydrogen bond networks and flexible blocks

The preparation of polymers with high self-healing ability is conducive to environmental protection and resource conservation. In the present work, two kinds of polyurethane (PU) elastomers were prepared: the one containing flexible end blocks (polypropylene glycol) and the other containing flexible end blocks and 2-ureido-4[1H]-pyrimidinone (UPy) groups that can form reversible quadruple hydrogen bonds. Both of the two PU elastomers have self-healing ability. At low temperatures the PU without UPy groups exhibits stronger self-healing ability, while at high temperatures the PU with UPy groups has better self-healing function. The difference can be attributed to the combined effect of segmental mobility and reversible network strength. Based on molecular simulations, we further observed that the self-healing behaviors are affected by four factors: healing temperature, reversible interaction strength, reversible interaction site density and segment diffusion ability.

Fluorescent-Nanoparticle-Impregnated Nanocomposite Polymeric Gels for Biosensing and Drug Delivery Applications

Nanocomposite polymeric gels infused with fluorescent nanoparticles have surfaced as a propitious category of substances for biomedical purposes owing to their exceptional characteristics. The aforementioned materials possess a blend of desirable characteristics, including biocompatibility, biodegradability, drug encapsulation, controlled release capabilities, and optical properties that are conducive to imaging and tracking. This paper presents a comprehensive analysis of the synthesis and characterization of fluorescent-nanoparticle-impregnated nanocomposite polymeric gels, as well as their biomedical applications, such as drug delivery, imaging, and tissue engineering. In this discourse, we deliberate upon the merits and obstacles linked to these substances, encompassing biocompatibility, drug encapsulation, optical characteristics, and scalability. The present study aims to provide an overall evaluation of the potential of fluorescent-nanoparticle-impregnated nanocomposite polymeric gels for biomedical applications. Additionally, emerging trends and future directions for research in this area are highlighted.

Recent Advances in Triboelectric Nanogenerators: From Technological Progress to Commercial Applications

Serious climate changes and energy-related environmental problems are currently critical issues in the world. In order to reduce carbon emissions and save our environment, renewable energy harvesting technologies will serve as a key solution in the near future. Among them, triboelectric nanogenerators (TENGs), which is one of the most promising mechanical energy harvesters by means of contact electrification phenomenon, are explosively developing due to abundant wasting mechanical energy sources and a number of superior advantages in a wide availability and selection of materials, relatively simple device configurations, and low-cost processing. Significant experimental and theoretical efforts have been achieved toward understanding fundamental behaviors and a wide range of demonstrations since its report in 2012. As a result, considerable technological advancement has been exhibited and it advances the timeline of achievement in the proposed roadmap. Now, the technology has reached the stage of prototype development with verification of performance beyond the lab scale environment toward its commercialization. In this review, distinguished authors in the world worked together to summarize the state of the art in theory, materials, devices, systems, circuits, and applications in TENG fields. The great research achievements of researchers in this field around the world over the past decade are expected to play a major role in coming to fruition of unexpectedly accelerated technological advances over the next decade.

A bibliometric survey of research trends in vitrimer

The recent trends of vitrimer studies enhance the thermoset material with superior properties, therefore, it is particularly important to address the critical scientific inquiries in this area using their research metrics. The reported vitrimer systems have been highly required for future real-time applications; however, the inquisitiveness of material exchange mechanisms extends the research studies further. Significantly, more scientific information's are required to achieve the evident prospective outcomes via these materials. This article highlights the trends and developments of the most relevant publications, authors, articles, countries, and keywords in the vitrimer research field over the past 10 years. The represented bibliometric survey would elevate the basic understanding of the current vitrimer research stats and also help follow the particular research community to learn and develop insight. To generate bibliometric networks, bibliometric data has obtained from Scopus and visualised in VOS-viewer; as an overview of that, the highest number of publications were from China, United States, France, United Kingdom, and Spain.

Improved PVC/ZnO Nanocomposite Insulation for High Voltage and High Temperature Applications

Nanosized inorganic oxides have the trends to improve many characteristics of solid polymer insulation. In this work, the characteristics of improved poly (vinyl chloride) (PVC)/ZnO are evaluated using 0, 2, 4 and 6 phr of ZnO nanoparticles dispersed in polymer matrix using internal mixer and finally compressed into circular disk with 80 mm diameter using compression molding technique. Dispersion properties are studied by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), and optical microscopy (OM). The effect of filler on the electrical, optical, thermal, and dielectric properties of the PVC are also analyzed. Hydrophobicity of nano-composites is evaluated by measuring contact angle and recording hydrophobicity class using Swedish transmission research institute (STRI) classification method. Hydrophobic behavior decreases with the increase in filler content; contact angle increases up to 86°, and STRI class of HC3 for PZ4 is observed. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) are employed to evaluate the thermal properties of the samples. Also, continuous decrease of optical band gap energy from 4.04 eV for PZ0 to 2.57 eV for PZ6 is observed. In the meantime, an enhancement in the melting temperature, T_m, is observed from 172 to 215 °C. To check the stability of materials against hydrothermal stresses, all the fabricated materials are then subjected to a hydrothermal aging process for 1000 h and their structural stability is analyzed using optical microscopy and FTIR analyses.

Innovative Device and Procedure for In Situ Quantification of the Self-Healing Ability and Kinetics of Self-Healing of Polymeric Materials

A new device and procedure for the in situ quantification of the extent of the self-healing and the kinetics of self-healing of polymeric materials were proposed. The device consisted of flowing an inert gas below the sample placed in a hermetically closed chamber. When the sample was perforated/damaged, the gas passed through the hole made in the polymeric material and the gas flow rate declined as the self-healing was produced. Once the gas flow rate stopped, the self-healing was completed. The proposed method was simple, quick, and reproducible, and several in situ self-healing experiments at different temperatures could be performed in the same sample. As a proof of concept, the new device and method have been used for measuring the self-healing ability of different polyurethanes.

Nanocomposite of CO2-Based Polycarbonate Polyol with Highly Exfoliated Nanoclay

Polypropylene carbonate (PPC) derived from carbon dioxide has been used as a precursor for the synthesis of polyurethane (PU). The high viscosity of the PPC is the key parameter hindering its processability during PU synthesis. Herein, a PPC nanocomposite with highly exfoliated nanoclay was prepared through a solution intercalation process. A wide range of nanoclay concentrations incorporated into the PPC were studied. The impacts of the nanoclay on the PPC were investigated in order to maintain the polymer structure while improving its physical properties. The characterizations of PPC nanocomposites showed that the highly exfoliated nanoclay contributed to a viscosity reduction, and a slight reduction in the molecular weight. The polymer degradation was indicated by the formation of cyclic propylene carbonate. The minimum or critical concentration of nanoclay was found to be between ∼0.5 and 2.0 wt %. Within this range, the polymer degradation is minimal. The PPC nanocomposites with a lower viscosity showed excellent precursors for making PU coating materials. The PU coating derived from the PPC nanocomposite has higher anticorrosive properties in comparison with the non-modified PU coating.

Sustainable smart anti-corrosion coating materials derived from vegetable oil derivatives: a review

Sustainable development is a critical concern in this fast-paced technological world. Therefore, it is essential to employ renewable resources to move towards sustainable development goals (SDGs). The polyols attained from renewable resources, including lignin, chitosan, vegetable oils, cellulose, etc. and the polymers derived from them have attracted the attention of the majority of researchers, both in academia and industry. The development of bio-based polymers from vegetable oils start emerging with different properties to generate a value-added system. This review will give an impression to readers about how coatings generated from vegetable oils can find a way towards better protective properties against corrosion either by using fillers or by using molecular structure modifications in the system, thus covering a range of vegetable oil-based self-healing polymers and their application in anti-corrosion coatings.

Creep and Recovery Behavior of Vitrimers with Fast Bond Exchange Rate

Vitrimers encompass the desirable mechanical properties of thermosets with the recyclability of thermoplastics. This ability arises from the rearrangement of the vitrimer covalent network upon heating via a bond shuffling mechanism while its cross-link density remains preserved. This unique feature makes vitrimers interesting candidates for the design of materials that combine dimensional stability at high temperatures and solvent resistance with the ability to be reshaped and processed. Despite these advantages, vitrimer exhibits significant creep at operating conditions where thermosets show little or no creep. As the mechanical properties of vitrimers not only depend on their chemical composition but also on the dynamics of the polymer chains, molecular dynamics (MD) simulations can provide detailed molecular mechanisms of the system of interest under macroscopic stress-induced deformations. In this regard, the recently developed MD/Monte Carlo simulation methodology capable of capturing the bond exchange mechanics in vitrimers is used to study the creep and recovery response of a coarse-grained model thermoset and vitrimer with a fast bond exchange rate. The time-stress superposition principle is then successfully applied to the creep response. The resulting universal curves enable us to predict the long-time creep behavior of both systems extending the timescale from 4 to over 10 orders of magnitude.

Self-healing properties of retrograded starch films with enzyme-treated waxy maize starch as healing agent

Waxy maize starch (WMS) was modified using sequential α-amylase and transglucosidase to create enzyme-treated waxy maize starch (EWMS) with higher branching degree and lower viscosity as an ideal healing agent. Self-healing properties of retrograded starch films with microcapsules containing WMS (WMC) and EWMS (EWMC) were investigated. The results indicated that EWMS-16 had the maximum branching degree of 21.88 % after transglucosidase treatment time of 16 h, and A chain of 12.89 %, B1 chain of 60.76 %, B2 chain of 18.82 % and B3 chain of 7.52 %. The particle sizes of EWMC ranged from 2.754 to 5.754 μm. The embedding rate of EWMC was 50.08 %. Compared to retrograded starch films with WMC, water vapor transmission coefficients of retrograded starch films with EWMC were lower, while tensile strength and elongation at break values of retrograded starch films were almost similar. Retrograded starch films with EWMC had higher healing efficiency of 58.33 % as compared to that Retrograded starch films retrograded starch films with WMC was 44.65 %.

Opportunities of Flexible and Portable Electrochemical Devices for Energy Storage: Expanding the Spotlight onto Semi-solid/Solid Electrolytes

The ever-increasing demand for flexible and portable electronics has stimulated research and development in building advanced electrochemical energy devices which are lightweight, ultrathin, small in size, bendable, foldable, knittable, wearable, and/or stretchable. In such flexible and portable devices, semi-solid/solid electrolytes besides anodes and cathodes are the necessary components determining the energy/power performances. By serving as the ion transport channels, such semi-solid/solid electrolytes may be beneficial to resolving the issues of leakage, electrode corrosion, and metal electrode dendrite growth. In this paper, the fundamentals of semi-solid/solid electrolytes (e.g., chemical composition, ionic conductivity, electrochemical window, mechanical strength, thermal stability, and other attractive features), the electrode-electrolyte interfacial properties, and their relationships with the performance of various energy devices (e.g., supercapacitors, secondary ion batteries, metal-sulfur batteries, and metal-air batteries) are comprehensively reviewed in terms of materials synthesis and/or characterization, functional mechanisms, and device assembling for performance validation. The most recent advancements in improving the performance of electrochemical energy devices are summarized with focuses on analyzing the existing technical challenges (e.g., solid electrolyte interphase formation, metal electrode dendrite growth, polysulfide shuttle issue, electrolyte instability in half-open battery structure) and the strategies for overcoming these challenges through modification of semi-solid/solid electrolyte materials. Several possible directions for future research and development are proposed for going beyond existing technological bottlenecks and achieving desirable flexible and portable electrochemical energy devices to fulfill their practical applications. It is expected that this review may provide the readers with a comprehensive cross-technology understanding of the semi-solid/solid electrolytes for facilitating their current and future researches on the flexible and portable electrochemical energy devices.

Rheological, Thermal and Mechanical Characterization of Toughened Self-Healing Supramolecular Resins, Based on Hydrogen Bonding

This paper proposes the design of toughened self-healing supramolecular resins able to fulfill functional and structural requirements for industrial applications. These new nanocomposites are based on compounds acting as promotors of reversible self-healing interactions. Electrically conductive carbon nanotubes, selected among those allowing to reach the electrical percolation threshold (EPT) with a very low amount of nanofiller, were dispersed in the self-healing polymeric matrix to contrast the electrical insulating properties of epoxy matrices, as required for many applications. The formulated supramolecular systems are thermally stable, up to 360 °C. Depending on the chemical formulation, the self-healing efficiency η, assessed by the fracture test, can reach almost the complete self-repairing efficiency (η = 99%). Studies on the complex viscosity of smart nanocomposites highlight that the effect of the nanofiller dominates over those due to the healing agents. The presence of healing compounds anchored to the hosting epoxy matrix determines a relevant increase in the glass transition temperature (T_g), which results in values higher than 200 °C. Compared to the unfilled matrix, a rise from 189 °C to 223 °C is found for two of the proposed formulations.

Self-healable fiber-reinforced vitrimer composites: overview and future prospects

To achieve sustainable development goals, approaches towards the preparation of recyclable and healable polymeric materials is highly attractive. Self-healing polymers and thermosets based on bond-exchangeable dynamic covalent bonds, so called "vitrimers" could be a great effort in this direction. In order to match the industrial importance, enhancement of mechanical strength without sacrificing the bond exchange capability is a challenging issue, however, such concerns can be overcome through the developments of fiber-reinforced vitrimer composites. This article covers the outstanding features of fiber-reinforced vitrimer composites, including their reprocessing, recycling and self-healing properties, together with practical applications and future perspectives of this unique class of materials.

Graphene and Its Derivatives: Synthesis and Application in the Electrochemical Detection of Analytes in Sweat

Wearable sensors and invasive devices have been studied extensively in recent years as the demand for real-time human healthcare applications and seamless human-machine interaction has risen exponentially. An explosion in sensor research throughout the globe has been ignited by the unique features such as thermal, electrical, and mechanical properties of graphene. This includes wearable sensors and implants, which can detect a wide range of data, including body temperature, pulse oxygenation, blood pressure, glucose, and the other analytes present in sweat. Graphene-based sensors for real-time human health monitoring are also being developed. This review is a comprehensive discussion about the properties of graphene, routes to its synthesis, derivatives of graphene, etc. Moreover, the basic features of a biosensor along with the chemistry of sweat are also discussed in detail. The review mainly focusses on the graphene and its derivative-based wearable sensors for the detection of analytes in sweat. Graphene-based sensors for health monitoring will be examined and explained in this study as an overview of the most current innovations in sensor designs, sensing processes, technological advancements, sensor system components, and potential hurdles. The future holds great opportunities for the development of efficient and advanced graphene-based sensors for the detection of analytes in sweat.

Bio-Vitrimers for Sustainable Circular Bio-Economy

The aim to achieve sustainable development goals (SDG) and cut CO₂-emission is forcing researchers to develop bio-based materials over conventional polymers. Since most of the established bio-based polymeric materials demonstrate prominent sustainability, however, performance, cost, and durability limit their utilization in real-time applications. Additionally, a sustainable circular bioeconomy (CE) ensures SDGs deliver material production, where it ceases the linear approach from production to waste. Simultaneously, sustainable circular bio-economy promoted materials should exhibit the prominent properties to involve and substitute conventional materials. These interceptions can be resolved through state-of-the-art bio-vitrimeric materials that display durability/mechanical properties such as thermosets and processability/malleability such as thermoplastics. This article emphasizes the current need for vitrimers based on bio-derived chemicals; as well as to summarize the developed bio-based vitrimers (including reprocessing, recycling and self-healing properties) and their requirements for a sustainable circular economy in future prospects.

An investigated organic and inorganic reinforcement as an effective economical filler of poly (methyl methacrylate) nanocomposites

Polymer matrix composites have garnered the interest of the dentistry sector. Nano-fillers are frequently used as reinforcements in these composites to enhance their characteristics. Poly (methyl methacrylate) was filled with date seed nanoparticles (DSNP) and titanium oxide nanoparticles (TiO₂NP). In this work, two nanofillers (DSNP and TiO₂NP) were analyzed using Fourier-transform infrared spectroscopy (FTIR). In addition, the features of the PMMA-nanofiller composite were experimentally evaluated via compression, micro-hardness, wear rate (WR), and coefficients of friction (µ) testing. Utilizing a scanning electron microscope (SEM), the microstructure of the PMMA-DSNP composite was examined. The results of the experiments on the nanocomposites demonstrated that the elastic modulus, microhardness, wear resistance, and friction resistance increased with an increase in DSNP content to 1.2 wt, in comparison to TiO₂NP at the same concentration. Finally, according to the guidelines, the ideal weight was determined to be 1.2 wt%, filler in the form of DSNP, at a normal load of 10 N.

Ionic Liquid-Based Polymer Nanocomposites for Sensors, Energy, Biomedicine, and Environmental Applications: Roadmap to the Future

Current interest toward ionic liquids (ILs) stems from some of their novel characteristics, like low vapor pressure, thermal stability, and nonflammability, integrated through high ionic conductivity and broad range of electrochemical strength. Nowadays, ionic liquids represent a new category of chemical-based compounds for developing superior and multifunctional substances with potential in several fields. ILs can be used in solvents such as salt electrolyte and additional materials. By adding functional physiochemical characteristics, a variety of IL-based electrolytes can also be used for energy storage purposes. It is hoped that the present review will supply guidance for future research focused on IL-based polymer nanocomposites electrolytes for sensors, high performance, biomedicine, and environmental applications. Additionally, a comprehensive overview about the polymer-based composites' ILs components, including a classification of the types of polymer matrix available is provided in this review. More focus is placed upon ILs-based polymeric nanocomposites used in multiple applications such as electrochemical biosensors, energy-related materials, biomedicine, actuators, environmental, and the aviation and aerospace industries. At last, existing challenges and prospects in this field are discussed and concluding remarks are provided.

Glycidyl Methacrylate-Based Copolymers as Healing Agents of Waterborne Polyurethanes

Self-healing materials and self-healing mechanisms are two topics that have attracted huge scientific interest in recent decades. Macromolecular chemistry can provide appropriately tailored functional polymers with desired healing properties. Herein, we report the incorporation of glycidyl methacrylate-based (GMA) copolymers in waterborne polyurethanes (WPUs) and the study of their potential healing ability. Two types of copolymers were synthesized, namely the hydrophobic P(BA-co-GMAy) copolymers of GMA with n-butyl acrylate (BA) and the amphiphilic copolymers P(PEGMA-co-GMAy) of GMA with a poly(ethylene glycol) methyl ether methacrylate (PEGMA) macromonomer. We demonstrate that the blending of these types of copolymers with two WPUs leads to homogenous composites. While the addition of P(BA-co-GMAy) in the WPUs leads to amorphous materials, the addition of P(PEGMA-co-GMAy) copolymers leads to hybrid composite systems varying from amorphous to semi-crystalline, depending on copolymer or blend composition. The healing efficiency of these copolymers was explored upon application of two external triggers (addition of water or heating). Promising healing results were exhibited by the final composites when water was used as a healing trigger.

A Microvascular System Self-Healing Approach on Polymeric Composite Materials

The paper addresses the synthesis of a nano-fibre network by coaxial electrospinning, embedding the healing agent dicyclopentadiene (DCPD) in polyacrylonitrile (PAN) fibres. Compared to other encapsulation methods, the use of nano-fibres filled with healing agent have no effect on the mechanical properties of the matrix and can address a larger healing area. Additionally, carbon nanotubes were added as nanofillers to enhance the reactivity between DCPD and the epoxydic matrix. The self-healing capability of the nano-fibre network was carried out by flexural tests, at epoxy resin level and composite level. Results obtained from Fourier transform infrared (FTIR) spectrometry, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) confirmed the successful encapsulation of DCPD healing agent in PAN fibres. Flexural tests indicate that after 48 h, the epoxy resin has recovered 84% of its flexural strength while the composite material recovered 93%.

Special Issue: Advanced Science and Technology of Polymer Matrix Nanomaterials

Nanotechnology has witnessed an incredible resonance and a substantial number of new applications in various areas during the past three decades [...]

Magnetic Self-Healing Composites: Synthesis and Applications

Magnetic composites and self-healing materials have been drawing much attention in their respective fields of application. Magnetic fillers enable changes in the material properties of objects, in the shapes and structures of objects, and ultimately in the motion and actuation of objects in response to the application of an external field. Self-healing materials possess the ability to repair incurred damage and consequently recover the functional properties during healing. The combination of these two unique features results in important advances in both fields. First, the self-healing ability enables the recovery of the magnetic properties of magnetic composites and structures to extend their service lifetimes in applications such as robotics and biomedicine. Second, magnetic (nano)particles offer many opportunities to improve the healing performance of the resulting self-healing magnetic composites. Magnetic fillers are used for the remote activation of thermal healing through inductive heating and for the closure of large damage by applying an alternating or constant external magnetic field, respectively. Furthermore, hard magnetic particles can be used to permanently magnetize self-healing composites to autonomously re-join severed parts. This paper reviews the synthesis, processing and manufacturing of magnetic self-healing composites for applications in health, robotic actuation, flexible electronics, and many more.

Self-Healing Polymers and Composites: Extrinsic Routes

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Polymers have the property to convert the physical stress to covalent bond shuffling, thereby acting as the healing agents. Polymeric coatings, paints, electronic devices, drug delivery, and many other applications find self-healing materials as a smart technique to prolong the life cycle of the end products. The idea behind these artificial materials is to make them behave like the human body. It should sense the failure and repair it before it becomes worse or irreparable. Researchers have explored several polymeric materials which can self-heal through intrinsic or extrinsic mechanisms. This review specifically focuses on extrinsic routes governed by mechanical stress, temperature change in a covalent bond, humidity, variation in pH, optical sensitivity, and electrochemical effects. Each possible mechanism is further supported by the molecules or bonds which can undergo the transformations under given conditions. On a broader scale, bonds that can self-repair by mechanical force, thermal treatment, chemical modifications, UV irradiation, or electromagnetic phenomenon are covered under this review. It brings into the notice the shortcomings or challenges in adopting the technology to the commercial scale. The possible molecules or bonds which can undergo self-healing under certain conditions have been distinctly presented in a well-segregated manner. This review is envisaged to act as a guide for researchers working in this area.

Environment tolerant, adaptable and stretchable organohydrogels: preparation, optimization, and applications

Multiple stretchable materials have been successively developed and applied to wearable devices, soft robotics, and tissue engineering. Organohydrogels are currently being widely studied and formed by dispersing immiscible hydrophilic/hydrophobic polymer networks or only hydrophilic polymer networks in an organic/water solvent system. In particular, they can not only inherit and carry forward the merits of hydrogels, but also have some unique advantageous features, such as anti-freezing and water retention abilities, solvent resistance, adjustable surface wettability, and shape memory effect, which are conducive to the wide environmental adaptability and intelligent applications. This review first summarizes the structure, preparation strategy, and unique advantages of the reported organohydrogels. Furthermore, organohydrogels can be optimized for electro-mechanical properties or endowed with various functionalities by adding or modifying various functional components owing to their modifiability. Correspondingly, different optimization strategies, mechanisms, and advanced developments are described in detail, mainly involving the mechanical properties, conductivity, adhesion, self-healing properties, and antibacterial properties of organohydrogels. Moreover, the applications of organohydrogels in flexible sensors, energy storage devices, nanogenerators, and biomedicine have been summarized, confirming their unlimited potential in future development. Finally, the existing challenges and future prospects of organohydrogels are provided.

Self-Healing Thiolated Pillar[5]arene Films Containing Moxifloxacin Suppress the Development of Bacterial Biofilms

Polymer self-healing films containing fragments of pillar[5]arene were obtained for the first time using thiol/disulfide redox cross-linking. These films were characterized by thermogravimetric analysis and differential scanning calorimetry, FTIR spectroscopy, and electron microscopy. The films demonstrated the ability to self-heal through the action of atmospheric oxygen. Using UV–vis, 2D 1H-1H NOESY, and DOSY NMR spectroscopy, the pillar[5]arene was shown to form complexes with the antimicrobial drug moxifloxacin in a 2:1 composition (logK11 = 2.14 and logK12 = 6.20). Films containing moxifloxacin effectively reduced Staphylococcus aureus and Klebsiella pneumoniae biofilms formation on adhesive surfaces.

The Final Frontier of Sustainable Materials: Current Developments in Self-Healing Elastomers

It is impossible to describe the recent progress of our society without considering the role of polymers; however, for a broad audience, "polymer" is usually related to environmental pollution. The poor disposal and management of polymeric waste has led to an important environmental crisis, and, within polymers, plastics have attracted bad press despite being easily reprocessable. Nonetheless, there is a group of polymeric materials that is particularly more complex to reprocess, rubbers. These macromolecules are formed by irreversible crosslinked networks that give them their characteristic elastic behavior, but at the same time avoid their reprocessing. Conferring them a self-healing capacity stands out as a decisive approach for overcoming this limitation. By this mean, rubbers would be able to repair or restore their damage automatically, autonomously, or by applying an external stimulus, increasing their lifetime, and making them compatible with the circular economy model. Spain is a reference country in the implementation of this strategy in rubbery materials, achieving successful self-healable elastomers with high healing efficiency and outstanding mechanical performance. This article presents an exhaustive summary of the developments reported in the previous 10 years, which demonstrates that this property is the last frontier in search of truly sustainable materials.

Synthesis of TiO2 nanogel composite for highly efficient self-healing epoxy coating

INTRODUCTION

Organic coatings are the most effective and facile methods of protecting steel against corrosion, which shields it from direct contact with oxygen and moisture. However, they are inherently defective and susceptible to damage, which allows the penetration of the corrosive media into the underlying substrates. Self-healing coatings were developed to address this shortcoming.

OBJECTIVE

The current research aims to develop a coating with superior self-healing ability via embedment of titanium dioxide (TiO₂) nanogel composite (NC) in a commercial epoxy.

METHODS

The TiO₂ NC was prepared by efficient dispersion of TiO₂ nanoparticles in copolymer gel of acrylamide (AAm) and 2-acrylamido-2-methyl propane sulfonic acid (AMPS) with the help of 3-(trimethoxysilyl) propyl methacrylate (MPS). The chemical structure, morphology, and thermal properties of the modified and functionalized nanoparticles were assessed by infrared spectroscopy, electron microscopy, X-ray diffraction, and thermogravimetric analysis, respectively. In addition, TiO₂ nanoparticles, nano-TiO₂ functionalized monomer (NTFM), and NTFM/AAm/AMPS in different weight percentages were incorporated into epoxy resin to prepare a self-healing coating.

RESULTS

The results confirmed the successful fabrication of the NC. In addition, the incorporation of 1 wt% NTFM/AAm/AMPS led to homogenous dispersion, enhanced anti-corrosive and self-healing performance with the healing efficiencies of 100% and 98%, which were determined by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods, respectively.

CONCLUSION

The prepared NC was sensitive towards salt concentration, pH, which aids the quick reaction of the TiO₂ NC to corrosive ions, once the cracks occur. In addition, this is a unique feature compared to the other self-healing mechanisms, especially, the encapsulation of healing agents, which can be effective as long as the healing agent is present.

Nanomaterials for IoT Sensing Platforms and Point-of-Care Applications in South Korea

Herein, state-of-the-art research advances in South Korea regarding the development of chemical sensing materials and fully integrated Internet of Things (IoT) sensing platforms were comprehensively reviewed for verifying the applicability of such sensing systems in point-of-care testing (POCT). Various organic/inorganic nanomaterials were synthesized and characterized to understand their fundamental chemical sensing mechanisms upon exposure to target analytes. Moreover, the applicability of nanomaterials integrated with IoT-based signal transducers for the real-time and on-site analysis of chemical species was verified. In this review, we focused on the development of noble nanostructures and signal transduction techniques for use in IoT sensing platforms, and based on their applications, such systems were classified into gas sensors, ion sensors, and biosensors. A future perspective for the development of chemical sensors was discussed for application to next-generation POCT systems that facilitate rapid and multiplexed screening of various analytes.

Nanocomposite Materials: A Section of Nanomaterials

"Nanocomposite materials" is one of the main sections of Nanomaterials and it has contributed with more than 440 publications during the last two years to increase the reputation and recognition of the journal by the scientific community [...].

Recent Advances in Zwitterionic Hydrogels: Preparation, Property, and Biomedical Application

Nonspecific protein adsorption impedes the sustainability of materials in biologically related applications. Such adsorption activates the immune system by quick identification of allogeneic materials and triggers a rejection, resulting in the rapid failure of implant materials and drugs. Antifouling materials have been rapidly developed in the past 20 years, from natural polysaccharides (such as dextran) to synthetic polymers (such as polyethylene glycol, PEG). However, recent studies have shown that traditional antifouling materials, including PEG, still fail to overcome the challenges of a complex human environment. Zwitterionic materials are a class of materials that contain both cationic and anionic groups, with their overall charge being neutral. Compared with PEG materials, zwitterionic materials have much stronger hydration, which is considered the most important factor for antifouling. Among zwitterionic materials, zwitterionic hydrogels have excellent structural stability and controllable regulation capabilities for various biomedical scenarios. Here, we first describe the mechanism and structure of zwitterionic materials. Following the preparation and property of zwitterionic hydrogels, recent advances in zwitterionic hydrogels in various biomedical applications are reviewed.

Self-Healing Materials for Electronics Applications

Self-healing materials have been attracting the attention of the scientists over the past few decades because of their effectiveness in detecting damage and their autonomic healing response. Self-healing materials are an evolving and intriguing field of study that could lead to a substantial increase in the lifespan of materials, improve the reliability of materials, increase product safety, and lower product replacement costs. Within the past few years, various autonomic and non-autonomic self-healing systems have been developed using various approaches for a variety of applications. The inclusion of appropriate functionalities into these materials by various chemistries has enhanced their repair mechanisms activated by crack formation. This review article summarizes various self-healing techniques that are currently being explored and the associated chemistries that are involved in the preparation of self-healing composite materials. This paper further surveys the electronic applications of self-healing materials in the fields of energy harvesting devices, energy storage devices, and sensors. We expect this article to provide the reader with a far deeper understanding of self-healing materials and their healing mechanisms in various electronics applications.