Mechanism Insights in Anticorrosion Performance of Waterborne Epoxy Coatings Reinforced by PEI-Functionalized Boron Nitride Nanosheets.

Functionalized hexagonal boron nitride nanosheets (BNNSs) have arisen as compelling anticorrosive additives, yet the precise mechanism of their corrosion resistance enhancement in coatings remains unclear. Here, polyethylenimine functionalized BNNSs (PEI-BNNSs) with approximately 6-11 layers were prepared through a "one-step" method. Then, the PEI-BNNSs/Waterborne epoxy (WEP) composite coatings were incorporated via the waterborne latex blending method for the anticorrosion of the Q235 substrate. The impedance modulus (|Z|f = 0.01 Hz) of 0.5 wt % PEI-BNNSs/WEP composite coating soaked in 3.5 wt % NaCl solution for 35 days increased by 4 orders of magnitude compared to pure WEP coating, exhibiting exceptional long-term resistance against corrosion. The positron annihilation lifetime spectroscopy and corrosion product analysis demonstrated that the reinforced anticorrosion capabilities are not solely ascribed to the "tortuous path effect" arising from BNNSs impermeability. These mechanisms also encompass the reduction in free volume fraction and radius of the free volume cavities within the composite coating brought about by the PEI molecules. Additionally, the increase in coating adhesion, promoted by PEI, plays an important role in augmenting the barrier properties against corrosive agents. This study provided a full comprehension of the role played by functionalized BNNSs in fortifying the anticorrosion attributes of WEP coatings.

Design and Analysis of a Textured Cu-Encapsulated Ni Tube for Low-Reflection Electromagnetic Interference Shielding Material.

With the frequent increase and update of electromagnetic interference (EMI) shielding materials, a low-resolution material that can absorb most electromagnetic waves, thereby effectively reducing the secondary pollution, is urgently needed. However, the excellent performance, flexibility, and low cost of these methods are usually incompatible with current reports. To address the above dilemma, we reported a facile solution for fabricating a low-reflection and high-performance EMI shielding composite by means of electroless nickel plating (EP-Ni), electroless copper plating (EP-Cu), annealing, and coating with a polydimethylsiloxane (PDMS) polymer with the structure of a Ni@Cu tube encapsulated with PDMS. The results indicate that the active groups on vegetable wool can act as active sites for the absorption of the Pd catalyst, thereby catalyzing the reduction of Ni2+, Cu2+, and the subsequent deposition on the plant fiber surface. Notably, the Ni@Cu-encapsulated plant fibers decreased during annealing at 100 °C. According to the segregated network and synergistic effect of the porous structure, the as-fabricated EMI shielding material demonstrated high absorption and low reflection, in which the power coefficient of the T value was approximately 0.0001, the R value was about 0.1764 (a decrease of 27.5% compared that of EP-Ni cotton), and the A value was approximately 0.8235.

Fabrication of Electrode Material for Textile-Based Triboelectric Nanogenerators: Research of the Relationship between Output Performance and Dielectric Material Strain.

In this work, a textile-based triboelectric nanogenerator (TENG) device was developed through electroless plating technology to prepare electrode material. Hydrophilic groups on the fiber surface are able to absorb Ag+, which could play a role in the center of a catalyst to reduce Cu2+ to fabricate Cu-coated cotton toward the fabrication of TENG electrode material. The TENG device established admirable performance and good stabilization, and a maximum voltage at 9.6 V was detected when the stress and strain on the polydimethylsiloxane layer are 82.6 kPa and 5.8%, respectively. In addition, the relationships among device properties and strain/thickness of dielectric materials have been explored in depth as well. The output voltage of the device increases gradually with the enhancement of dielectric strain and stress. As expected, the TENG as-fabricated device was installed to various physical behaviors to illustrate the harvesting of power of knee-jerk movements.

Dynamic Covalent Bonded Gradient Structured Actuators with Mechanical Robustness and Self-Healing Ability.

Flexible actuators with excellent adaptability and interaction safety have a wide range of application prospects in many fields. However, current flexible actuators have problems such as fragility and poor actuating ability. Here, inspired by the features of nacre structure, a gradient structured flexible actuator is proposed with mechanical robustness and self-healing ability. By introducing dynamic boronic ester bonds at the interface between MXene nanosheets and epoxy natural rubber matrix, the resulting nanocomposites with ordered micro-nano structures exhibit excellent tensile strength (25.03 MPa) and satisfactory repair efficiency (81.2%). In addition, the gradient distribution structure of MXene nanosheets endows the actuator with stable photothermal conversion capability, which can quickly respond to near-infrared light stimulation. The interlayer dynamic covalent bond crosslinking enables good response speed after multiple bending and is capable of functional self-healing after damage. This work introduces gradient structure and dynamic covalent bonding into flexible actuators, which provides a reference for the fabrication of self-healing soft robots, wearable, and other healable functional materials.

Highly Stretchable, Biodegradable, and Recyclable Green Electronic Substrates.

As a steady stream of electronic devices being discarded, a vast amount of electronic substrate waste of petroleum-based nondegradable polymers is generated, raising endless concerns about resource depletion and environmental pollution. With coupled reagent (CR)-grafted artificial marble waste (AMW@CR) as functional fillers, polylactic acid (PLA)-based highly stretchable biodegradable green composite (AMW@CR-SBGC) is prepared, with elongation at break up to more than 250%. The degradation mechanism of AMW@CR-SBGC is deeply revealed. AMW@CR not only contributed to the photodegradation of AMW@CR-SBGC but also significantly promoted the water degradation of AMW@CR-SBGC. More importantly, AMW@CR-SBGC showed great potential as sustainable green electronic substrates and AMW@CR-SBGC-based electronic skin can simulate the perception of human skin to strain signals. The outstanding programmable degradability, recyclability, and reusability of AMW@CR-SBGC enabled its application in transient electronics. As the first demonstration of artificial marble waste in electronic substrates, AMW@CR-SBGC killed three birds with one stone in terms of waste resourcing, e-waste reduction, and saving nonrenewable petroleum resources, opening up vast new opportunities for green electronics applications in areas such as health monitoring, artificial intelligence, and security.

Fabrication of a textile-based triboelectric nanogenerator toward high-efficiency energy harvesting and material recognition.

Textile-based triboelectric nanogenerator (T-TENG) devices, particularly, narrow-gap mode, have been conceived and developed for obtaining energy harvesting and tactile sensing devices unaffected by the external environment. Enhancing the interfacial area of T-TENG materials offers exciting opportunities to improve the device output performance. In this work, a narrow-gap T-TENG was fabricated with a facile process, and a new strategy for improving the device output is proposed. The new structural sensor (polydimethylsiloxane (PDMS)-encapsulated electroless copper plating (EP-Cu) cotton) with multiple electricity generation mechanism was designed and fabricated for enhancing recognition accuracy. The result shows that only PDMS layer strain was established at an external stress of 1.24-12.4 kPa and the fibers laterally slip at a stress of 12.4-139 kPa; more importantly, the output performance of the TENG displayed a linear relationship under corresponding stress ranges. The as-fabricated device demonstrated the ability to convert different energies such as vibration, raindrops, wind and human motions into electrical energy with excellent sensitivity. Interestingly, the output signal of the as-fabricated TENG device is a combination of output signals from PDMS/EP-Cu and PDMS/recognition object devices. To be precise, there are two TENG devices (PDMS/EP-Cu and PDMS/recognition object) that work when the as-fabricated TENG device is under 12.4-139 kPa stress. Accompanied by unique characteristics, the generated TENG signals are capable of recognition of contact materials. Combining the TENG signal and deep learning technology, we explore a strategy that can enable the as-fabricated device to recognize 8 different materials with 99.48% recognition accuracy in the natural environment.

Fabrication of Textured Ni-Coated Carbon Tubes for a Flexible Strain Sensor: Effect of the Device Elastic Modulus on Sensor Performance.

The exploration of flexible resistive sensors with excellent performance remains a challenge. In this paper, a nickel-coated carbon tube with a textured structure was prepared as a conductive sensitive material and inserted into the poly(dimethylsiloxane) (PDMS) polymer; interestingly, the sensor performance was controlled by the elastic modulus of the matrix resin. The results show that Pd2+ may be adsorbed by the active groups on the surface of a plant fiber as a catalytic center for the reduction of Ni2+. After 300 °C annealing, the inner plant fiber would be carbonized and attached to the outside of the nickel tube; to be precise, the textured Ni-encapsulated C tube was fabricated successfully. It is worth noting that the C tube serves as a layer of support for the external Ni coating, providing sufficient mechanical strength. In addition, resistance sensors with different properties were prepared by controlling the elasticity modulus of the PDMS polymer by introducing different contents of curing agents. The limit uniaxial tensile strain was enhanced from 42 to 49% and sensitivity reduced from 0.2 to 2.0% with the elasticity modulus of the matrix resin increasing from 0.32 to 2.2 MPa. As expected, the sensor is obviously appropriate for the detection of elbow joints, human speaking, and human joints with the reduction of the elasticity modulus of the matrix resin. To be precise, the optimal elastic modulus of the sensor matrix resin would facilitate the improvement of its sensitivity to monitor different human behaviors.

High-efficiency depolymerization/degradation of polyethylene terephthalate plastic by a whole-cell biocatalyst.

Polyethylene terephthalate (PET) is the most abundantly produced plastic due to its excellent performance, but is also the primary source of poorly degradable plastic pollution. The development of environment-friendly PET biodegradation is attracting increasing interest. The leaf-branch compost cutinase mutant ICCG (F243I/D238C/S283C/Y127G) exhibits the best hydrolytic activity and thermostability of all known PET hydrolases. However, its superior PET degradation is highly dependent on its preparation as a purified enzyme, which critically reduces its industrial utility. Herein, we report the use of rational design and combinatorial mutagenesis to develop a novel ICCG mutant RITK (D53R/R143I/D193T/E208K) that demonstrated excellent whole-cell biocatalytic activity. Whole cells expressing RITK showed an 8.33-fold increase in biocatalytic activity compared to those expressing ICCG. Thermostability was also improved. After reacting at 85 °C for 3 h, purified RITK exhibited a 12.75-fold increase in depolymerization compared to ICCG. These results will greatly enhance the industrial utility of PET hydrolytic enzymes and further the progress of PET recycling. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-023-03557-4.

Correction: Recent advances in self-healing polyurethane based on dynamic covalent bonds combined with other self-healing methods.

Correction for 'Recent advances in self-healing polyurethane based on dynamic covalent bonds combined with other self-healing methods' by Ze-Wei An et al., Nanoscale, 2023, 15, 6505-6520, https://doi.org/10.1039/D2NR07110J.

Fabrication of Ni-Encapsulated Carbon Tube/Poly(dimethylsiloxane) Composite Materials for Lightweight and Flexible Electromagnetic Interference Shielding Material.

The exploration of flexible and lightweight electromagnetic interference (EMI) shielding materials with excellent shielding effectiveness, as a means to effectively alleviate electromagnetic pollution, is still a tremendous challenge. This paper proposes a conducting material named the textured Ni-encapsulated carbon tube, which can be applied in EMI shielding material by being inserted in the center of a poly(dimethysiloxane) (PDMS) polymer. We demonstrated that Pd2+ could be absorbed by the active groups on the plant fiber surface to catalyze the reduction of Ni2+ as a catalytic center by means of a textured Ni-encapsulated plant fiber. Owing to the outstanding heat-conducting capability of the Ni coating, the inner plant fiber was carbonized and attached to the Ni-tube inside the surface during annealing. To be precise, the textured Ni-encapsulated C tube was fabricated successfully after annealing at 300 °C. On further increasing the annealing temperature, the C tube disappeared gradually with the Ni coating being oxidized to NiO. Of note, the C tube acted as a support layer for the external Ni coating, providing sufficient mechanical strength. When combined with the coating PDMS layer, a flexible and lightweight EMI shielding material is fabricated successfully. It displays an outstanding EMI shielding effectiveness of 31.34 dB and a higher specific shielding efficiency of 27.5 dB·cm3/g, especially showing excellent mechanical property and flexibility with only 2 mm thickness. This study provides a new method to fabricate outstanding EMI shielding materials.

Recent advances in self-healing polyurethane based on dynamic covalent bonds combined with other self-healing methods.

To meet more application requirements, improving mechanical properties and self-healing efficiency has become the focus of current research on self-healing PU. The competitive relationship between self-healing ability and mechanical properties cannot be avoided by a single self-healing method. To address this problem, a growing number of studies have combined dynamic covalent bonding with other self-healing methods to construct the PU structure. This review summarizes recent studies on PU materials that combine typical dynamic covalent bonds with other self-healing methods. It mainly includes four parts: hydrogen bonding, metal coordination bonding, nanofillers combined with dynamic covalent bonding and multiple dynamic covalent bond bonding. The advantages and disadvantages of different self-healing methods and their significant role in improving self-healing ability and mechanical properties in PU networks are analyzed. At the same time, the possible challenges and research directions of self-healing PU materials in the future are discussed.

Melting Behaviors of Bio-Based Poly(propylene 2,5-furan dicarboxylate)-b-poly(ethylene glycol) Co Polymers Related to Their Crystal Morphology.

In this experiment, a series of poly(propylene 2,5-furan dicarboxylate)-b-poly(ethylene glycol) (PPFEG) copolymers with different ratios were synthesized using melt polycondensation of dimethylfuran-2,5-dicarboxylate (DMFD), 1,3-propanediol (PDO) and poly(ethylene glycol) (PEG). The effect of PEG content on the crystallization behavior of the poly(propylene 2,5-furan dicarboxylate) (PPF) copolymers was investigated. For PPF, the nucleation density of the ß-crystals was higher than that of α-crystals. As Tc increases, the ß crystals are suppressed more, but at Tc = 140 °C, the bulk of PPF has already been converted to α crystals, which crystallize faster at higher nucleation densities, resulting in a difference in polymer properties. For this case, we chose to add a soft segment material, PEG, which led to an early multi-melt crystallization behavior of the PPF. The addition of PEG led to a decrease in the crystallization temperature of PPF, as well as a decrease in the cold crystallization peak of PPF. From the crystalline morphology, it can be seen that the addition of PEG caused the transformation of the PPF crystalline form to occur earlier. From the crystalline morphology of PPF at 155 °C, it can be observed that the ring-banded spherical crystals of the PPF appear slowly with increasing time. With the addition of PEG, spherical crystals of the ring band appeared earlier, and even appeared first, and then disappeared slowly.

The Impact of Artificial Marble Wastes on Heat Deflection Temperature, Crystallization, and Impact Properties of Polybutylene Terephthalate.

As artificial marble is abundant and widely used in residential and commercial fields, the resource utilization of artificial marble wastes (AMWs) has become extremely important in order to protect the environment. In this paper, polybutylene terephthalate/artificial marble wastes (PBT/AMWs) composites were prepared by melt blending to maximize resource utilization and increase PBT performance. The research results showed that the filling of AMWs was beneficial to the improvement of PBT-related performance. X-ray diffraction analysis results indicated that after filling AMWs into the PBT matrix, the crystal structure of PBT was not changed. Heat deflection temperature (HDT) analysis results indicated that the HDT of PBT composites with 20 wt% AMWs reached 66.68 °C, which was 9.12 °C higher than that of neat PBT. Differential scanning calorimetry analysis results showed that heterogeneous nucleation could be well achieved when the filling content was 15 wt%; impact and scanning electron microscope analysis results showed that due to the partial core-shell structure of the AMWs, the impact strength of PBT was significantly improved after filling. When the filling amount was 20 wt%, the impact strength of the PBT composites reached 23.20 kJ/m2, which was 17.94 kJ/m2 higher than that of neat PBT. This research will not only provide new insights into the efficient and high-value utilization of AMWs, but also provide a good reference for improved applications of other polymers.

A capillary-based SERS sensor for ultrasensitive and selective detection of Hg2+ by amalgamation with Au@4-MBA@Ag core-shell nanoparticles.

A capillary-based SERS sensor was fabricated for ultrasensitive and selective detection of Hg2+ in water. Au@Ag core-shell NPs embedded with 4-mercaptobenzoic acid (4-MBA) (Au@4-MBA@Ag) were prepared by a seed growth method and fixed on the inner wall of the glass capillary to obtain the sensor. Owing to the amalgamation between Ag and Hg, the capillary-based SERS sensor can specifically recognize the reduced Hg2+ without any recognition element, and the resulted Ag/Hg amalgam can weaken the SERS activity of Ag shell; thus, the SERS intensity of the embedded 4-MBA at 1075 cm-1 gradually decreased with the increase of Hg2+ concentration. Under the optimum condition, the fabricated sensor can sensitively determine Hg2+ in water with a limit of detection (LOD) as low as 0.03 nM. The capillary-based SERS sensor offers the advantages of simple preparation, superior stability, and high selectivity, which is promising for rapid and on-site detection of Hg2+ in water combined with a portable Raman device.

Superhydrophobic and Flexible Silver Nanowire-Coated Cellulose Filter Papers with Sputter-Deposited Nickel Nanoparticles for Ultrahigh Electromagnetic Interference Shielding.

Superhydrophobic, flexible, and ultrahigh-performance electromagnetic interference (EMI) shielding papers are of paramount importance to safety and long-term service under external mechanical deformations or other harsh service environments because they fulfill the growing demand for multipurpose materials. Herein, we fabricated multifunctional papers by incorporating sputter-deposited nickel nanoparticles (NiNPs) and a fluorine-containing coating onto cellulose filter papers coated with silver nanowires (AgNWs). AgNW networks with sputter-deposited NiNPs provide outstanding magnetic properties, electrical conductivity, and EMI shielding performance. At an AgNW content of 0.109 vol % and a NiNP content of 0.013 mg/cm2, the resultant papers exhibit a superior EMI shielding effectiveness (SE) of 88.4 dB. Additionally, the fluorine-containing coating endows the resultant papers with a high contact angle of 149.7°. Remarkably, the obtained papers still maintain a high EMI SE even after 1500 bending cycles or immersion in water, salt, or strong alkaline solutions for 2 h, indicating their outstanding mechanical robustness and chemical durability. This work opens a new window for designing and implementing ultrahigh-performance EMI shielding materials.

3D printing of robust and biocompatible poly(ethylene glycol)diacrylate/nano-hydroxyapatite composites via continuous liquid interface production.

Three-dimensional (3D) printing technology with satisfactory speed and accuracy has been a powerful force in biomaterial processing. Early studies on 3D printing of biomaterials mainly focused on their biocompatibility and cellular viability while rarely attempted to produce robust specimens. Nonetheless, the biomedical applications of polymers can be severely limited by their inherently weak mechanical properties particularly in bone tissue engineering. In this study, continuous liquid interface production (CLIP) is applied to construct 3D objects of nano-hydroxyapatite (n-HA) filled polymeric biomaterials with complex architectures. Notably, the bioactive and osteoconductive n-HA endows the 3D prints of poly(ethyleneglycol)diacrylate (PEGDA) composites with a high compression strength of 6.5 ± 1.4 MPa, about 342% improvement over neat PEGDA. This work demonstrates the first successful attempt on CLIP 3D printing of n-HA nanocomposites, providing a feasible, cost-effective and patient-specific solution to various fields in the biomedical industry.

Robust, flexible, and high-performance electromagnetic interference shielding films with long-lasting service.

It is of great significance for electromagnetic interference (EMI) shielding materials to fulfill long-lasting service requirements. Here, waterborne polyurethane (WPU) was coated on the surface of a silver nanowire (AgNW) network with sputter-deposited nickel nanoparticles (NiNPs) by dip-coating technology to improve their durability. After five dip-coating cycles, a WPU layer nearly coated the whole surface of the hybrid papers, and only a fraction of the metal filler is bare. The resultant hybrid papers exhibit an electrical conductivity of ∼3500 S m-1, remnant magnetization of 0.03 emu g-1, saturation magnetization of 0.10 emu g-1, and coercivity of 256 Oe. On the one hand, the presence of the WPU coating does not affect the shielding effectiveness (SE) of the hybrid papers; on the other hand, the WPU coating enhances the ability to resist tape peeling. Moreover, the resultant hybrid papers still maintain the original SE value (∼80 dB), even after exposure to air for 5 months owing to the isolation effect of the WPU coating, implying long-lasting durability. The results confirm that the obtained hybrid papers can meet the requirements of practical applications.

Biodegradable all-cellulose composite membranes for simultaneous oil/water separation and dye removal from water.

While of enormous scientific interests, the super-wetting materials capable of one-step separation of oils and dyes from water are rare on the market. Besides, the disposal of the used materials themselves is still a challenge, mainly ascribed to their non-biodegradation. Herein, we report an all-cellulose composite membrane that can simultaneously remove oil and dye from water. The membrane was fabricated via a simple dip-coating process during which the filter paper was coated by a cellulose hydrogel layer. This cellulose hydrogel coating was discovered to play an essential role in the separation of oil/water emulsion. Meanwhile, the incorporation of citric acid remarkably improved the mechanical and adsorption properties of the membrane as it served as both the crosslinking agent and the active species for methylene blue adsorption. This work demonstrated a new strategy on the development of fully biodegradable materials for both high-efficiency oil/water separation and dye removal.

Preparation and characterization of solvent-free fluids reinforced and plasticized polylactic acid fibrous membrane.

In this paper, the electronspun Polylactic acid (PLA)/TiO2 nanofluids (nfs) fibrous membrane with good toughness, hydrophilicity and antibacterial activities are fabricated by taking full advantages of solvent-free TiO2 nfs with amphiphilicity and ionic conductivity. The resulting PLA/TiO2 nfs fibrous membrane exhibits excellent mechanical performance with a tensile strength and elongation at break of 3.68 MPa and 97.32 MPa at 5 wt% loading, respectively, which is 4 and 8 times higher than that of pure PLA, respectively. Additionally, TiO2 nfs can migrate onto the surface of PLA fibers during electrospun process, which significantly enhanced hydrophilicity, antistatic property, moisture sorption capacity and wicking properties of PLA fabrics. Meanwhile, the membrane also showed ultrafast water filtration of 3500 L m-2 h-1 driven by gravity force, which is 10-12 times higher than that of commercial ultrafiltration membrane. After ion-exchange reaction with salt solution, excellent antibacterial activity (against E. coli and S. aureus was 95% and 99.9%, respectively) and separation efficiency (above 90% on E. coli) of the obtained fabrics are also achieved. Overall, organic nfs are an idea candidate for fabricating hydrophilic PLA based biodegradable fabric that can be applied in contaminated water treatment, antibacterial textiles and biodegradable absorption materials.

An anisotropic layer-by-layer carbon nanotube/boron nitride/rubber composite and its application in electromagnetic shielding.

Multifunctional polymer composites with anisotropic properties are attracting interest as they fulfil the growing demand of multitasking materials. In this work, anisotropic polymer composites have been fabricated by combining the layer-by-layer (LBL) filtration method with the alternative assembling of carbon nanotubes (CNTs) and hexagonal boron nitride flakes (hBN) on natural rubber latex particles (NR). The layered composites exhibit anisotropic thermal and electrical conductivities, which are tailored through the layer formulations. The best composite consists of four layers of NR modified with 8 phr (parts per Hundred Rubber) CNTs (∼7.4 wt%) and four alternate layers with 12 phr hBN (∼10.7 wt%). The composites exhibit an electromagnetic interference (EMI) shielding effectiveness of 22.41 ± 0.14 dB mm-1 at 10.3 GHz and a thermal conductivity equal to 0.25 W m-1 K-1. Furthermore, when the layered composite is used as an electrical thermal heater the surface reaches a stable temperature of ∼103 °C in approx. 2 min, with an input bias of 2.5 V.