Acid-Doped Pyridine-Based Polybenzimidazole as a Positive Triboelectric Material with Superior Charge Retention Capability

The energy conversion efficiency of a triboelectric nanogenerator (TENG) is severely limited by the charge density of triboelectric materials, while drastic and unavoidable charge decay happens during contact due to the insufficient charge retention capacity of positive triboelectric materials. Here, elaborately synthesized acid-ion-doped pyridine-based polybenzimidazole processing with strong charge retention capability is demonstrated to couple with negatively corona-polarized electrets. As illustrated by thermal stimulation and an ion mass spectrometer, the formation of acid-ion chimerism processes high activation energy for stored charges, and the selective anion migration can compensate the escape of polarized charge. Accordingly, the charge density can reach up to 596 μC m-2 and the charge retention rate reaches 49.7%, which is so far the highest intrinsic charge density obtained in the open air. Thus, the ionic chimerism strategy provides an effective way to suppress the charge escaping in the open air and gives a great expandable avenue for the material challenges of TENG's practical deployment.

Self-poled piezoelectric polymer composites via melt-state energy implantation

Lightweight flexible piezoelectric polymers are demanded for various applications. However, the low instinctively piezoelectric coefficient (i.e. d33) and complex poling process greatly resist their applications. Herein, we show that introducing dynamic pressure during fabrication is capable for poling polyvinylidene difluoride/barium titanate (PVDF/BTO) composites with d33 of ~51.20 pC/N at low density of ~0.64 g/cm3. The melt-state dynamic pressure driven energy implantation induces structure evolutions of both PVDF and BTO are demonstrated as reasons for self-poling. Then, the porous material is employed as pressure sensor with a high output of ~20.0 V and sensitivity of ~132.87 mV/kPa. Besides, the energy harvesting experiment suggests power density of ~58.7 mW/m2 can be achieved for 10 N pressure with a long-term durability. In summary, we not only provide a high performance lightweight, flexible piezoelectric polymer composite towards sustainable self-powered sensing and energy harvesting, but also pave an avenue for electrical-free fabrication of piezoelectric polymers.

Strengthening-toughening pure poly(lactic acid) with ultra-transparency through increasing mesophase promoted by elongational flow field

Poly(lactic acid) (PLA), as a biodegradable material, finds wide applications in packaging, automotive, and biological industries. However, achieving high strength, toughness, ultra-transparency, and heat resistance simultaneously in pure PLA through continuous one-step manufacturing remains a significant challenge. In this study, we addressed this challenge by utilizing the eccentric rotor extruder (ERE) in combination with cooling rolls to manufacture PLA sheets with outstanding mechanical performance. The ERE's elongational flow field combined with the cooling roller's weak stretching action induced orientation in the PLA molecular chains and promoted the formation of more mesophase, significantly improving mechanical properties. When the extrusion-stretch ratio (λ) value was 3.5, the tensile yield strength, Young's modulus, and elongation at break of ERE-fabricated samples ER-3.5 reached 86.2 MPa, 1777 MPa, and 57.9 %, respectively. Compared to the SE-3.5 samples manufactured with traditional methods, the increases were 38.8 %, 25.8 %, and 9.4 times, respectively. Additionally, the ERE manufactured samples maintained ultra-transparency and high heat resistance, making them suitable for food packaging, biomedicine, and other related fields. This methodology provides an efficient industrial-scale approach for manufacturing neat, biodegradable PLA with outstanding mechanical performance and ultra-transparency.

Water evaporation induced in-situ interfacial compatibilization for all-natural and high-strength straw-fiber/starch composites

In this paper, we proposed a novel and green strategy based on water evaporation induced in-situ interfacial compatibilization (WEIC) mechanism for fabricating high-strength and all-natural lignocellulose/starch composites. This mechanism exploits the natural compatibility of the lignocellulose and starch and was tested through an internal mixing process with regulated water evaporation. Specifically, we revealed that a restrained layer was in-situ formed at the interface of the lignocellulose and starch during the internal mixing process; a faster water evaporation rate thickens this restrained layer, restricts the starch's molecular movement and significantly increases the composite's mechanical properties. The highest tensile strength and Young's modulus of the composites achieved are 21.7 ± 0.8 MPa and 2.2 ± 0.1 GPa, respectively, superior to many existing starch/lignocellulose composites. Thus, this work provides new insight into the compatibilization of various hydrophilic polysaccharides and paves new avenues for developing greener and more facile methods to fabricate all-polysaccharide composites.

Layer-by-Layer Assembly of Multifunctional NR/MXene/CNTs Composite Films with Exceptional Electromagnetic Interference Shielding Performances and Excellent Mechanical Properties

With the rapid advance of electronics, the light, flexible, and multifunctional composite films with high electromagnetic interference (EMI) shielding effectiveness and excellent thermal management are highly desirable for next-generation portable and wearable electronic devices. Herein, a series of flexible and ultrathin natural rubber/MXene/carbon nanotubes (NR/MXene/CNTs) composite films with sandwich structure are constructed layer by layer through a facile vacuum-assisted filtration method for EMI shielding and Joule heating application. The fabricated NR/MXene/CNTs-50 composite film, with NR/MXene as inner layer and NR/CNTs as out layers, not only has high EMI shielding efficient, but also has excellent comprehensive mechanical properties at the thickness of only 200 µm. In addition, the superior environmental durability, high electrothermal conversion efficiency, hydrophobicity, and fine performance stability after periodic cyclic bending make the film possess more value in practical application.

One-step laser etching of a bionic hierarchical structure on a silicone rubber surface with thermal and acid/alkali resistance and tunable wettability

Superhydrophobic silicone rubbers with robust physical and chemical stability have promising application potential in the field of flexible electronics. A one-step laser etching strategy is proposed for successfully fabricating superhydrophobic silicone rubbers with bioinspired hierarchical micro/nanostructures. Regular and dense micro/nano spheres gradually accumulate on the modified silicone rubber surface with the increase of laser etching cycles. Owing to the bioinspired hierarchical micro/nano spheres, a 5 μL water droplet on the modified silicone rubber surface exhibits a contact angle of 158 ± 3° and a sliding angle of 5 ± 1°. Moreover, the modified silicone rubber can maintain a stable superhydrophobic state in acid/alkali (pH = 2, 4, 6, 8, and 10) and thermal environments (50-90 °C). Importantly, the contact angle and sliding angle are adjustable depending on the number of laser etching cycles, which is beneficial for the different application requirements. The proposed method for the fast fabrication of superhydrophobic silicone rubbers with tunable wettability can provide an excellent candidate for the protection of flexible electronics in rainy and acid/alkali environments.

Cost-Effective Fabrication of Micro-Nanostructured Superhydrophobic Polyethylene/Graphene Foam with Self-Floating, Optical Trapping, Acid-/Alkali Resistance for Efficient Photothermal Deicing and Interfacial Evaporation

Solar evaporation is one of the most attractive and sustainable approaches to address worldwide freshwater scarcity. Unfortunately, it is still a crucial challenge that needs to be confronted when the solar evaporator faces harsh application environments. Herein, a promising polymer molding method that combines melt blending and compression molding, namely micro extrusion compression molding, is proposed for the cost-effective fabrication of lightweight polyethylene/graphene nanosheets (PE/GNs) foam with interconnected vapor escape channels and surface micro-nanostructures. A contact angle of 155 ± 2°, a rolling angle of 5 ± 1° and reflectance of ≈1.6% in the wavelength range of 300-2500 nm appears on the micro-nanostructured PE/GNs foam surface. More interestingly, the micro-nanostructured PE/GNs foam surface can maintain a robust superhydrophobic state under dynamic impacting, high temperature and acid-/alkali solutions. These results mean that the micro-nanostructured PE/GNs foam surface possesses self-cleaning, anti-icing and photothermal deicing properties at the same time. Importantly, the foam exhibits an evaporation rate of 1.83 kg m^-2 h^-1 under 1 Sun illumination and excellent salt rejecting performance when it is used as a self-floating solar evaporator. The proposed method provides an ideal and industrialized approach for the mass production of solar evaporators suitable for practical application environments.

Ultrafast Fabrication of Graphene-Reinforced Nanocomposites via Synergy of Steam Explosion and Alternating Convergent-Divergent Flow

Producing high-quality graphene and polymer/graphene nanocomposite is facing the problems of complex procedure, low efficiency, and serious resource waste. To explore a new fabrication approach with high efficiency and low cost is crucial for solving these technical issues, which becomes a current research hotspot and also a great challenge. Herein, a one-step melt mixing strategy based on the synergy of steam explosion and alternating convergent-divergent flow, is innovatively developed to fabricate high-density polyethylene (HDPE)/graphene nanocomposites using industrial-grade expanded graphite (EG) without chemical agents and complex procedures. The co-action of the external force derived from elongational melts and the internal force generated by steam explosion make EG ultrafastly exfoliate into few-layer graphene nanosheets (GNS) and simultaneously disperse in melts within 4 min. The as-produced GNS have a lateral size of over 5 µm and a minimum thickness of 1.4 nm, can introduce super heterogeneous nucleation to HDPE macromolecules and greatly increases nanocomposite crystallinity up to 86.5%. Moreover, plentiful HDPE crystallites and well-dispersed GNS jointly form an improved thermally-conductive network, making nanocomposites with a rapid-respond ability in solar-to-thermal conversion and heat dissipation. This facile strategy will facilitate the development of scalable production and wide application of high-performance graphene and highly-filled nanocomposites.

Constructing Bone-Mimicking High-Performance Structured Poly(lactic acid) by an Elongational Flow Field and Facile Annealing Process

Poly(lactic acid) (PLA) as one of the most promising biodegradable polymers is being tremendously restricted in large-scale applications by the notorious toughness, ductility, and heat distortion resistance. Manufacturing PLA with excellent toughness, considerable ductility, balanced strength, and great heat distortion resistance simultaneously is still a great challenge. Natural structural materials usually possess excellent strength and toughness by elaborately constructed sophisticated hierarchical architectures, however, completely reproducing natural structural materials' architecture have evidenced to be difficult. Inspired by the hierarchical construction of the compact bone, an innovational method with an intensive and continuous elongational flow field and facile annealing process was developed to create bone-mimicking structured PLA at an industrial scale. The bone-mimicking structured PLA with unique and novel hierarchical architectures of interlocked 3D network lamellae and large extended-chain lamellae connecting the regular lamellae was constructed by in situ formed oriented thermoplastic poly(ether)urethane nanofibers (TNFs) acting as "collagen fibers", orderly staggered PLA lamellae behaving as "hydroxyapatite (HA) nanocrystals", and the tenacious interface functioning as a "soft protein" adhesive layer. Attributed to the unique structure, it possesses super toughness (90.3 KJ/m²), high stiffness (2.15 GPa), balanced strength (52.6 MPa), and notable heat distortion resistance (holding at 163 °C for 1 h) simultaneously. These excellent performances of the structured PLA provide it with immense potential applications in both structural and bio-engineering materials fields such as artificial bones and tissue scaffolds.

Phase Morphology and Performance of Supertough PLA/EMA-GMA/ZrP Nanocomposites Prepared through Reactive Melt-Blending

Nanofiller zirconium phosphate (ZrP) and ethylene-methyl acrylate-glycidyl methacrylate copolymer (EMA-GMA) were introduced into poly(lactic acid) (PLA) through reactive melt-blending method to improve its toughness. The impact strength of PLA/EMA-GMA/ZrP (82/15/3) nanocomposites was improved about 22 times that of pure PLA to 65.5 kJ/m2. Fourier transform infrared spectroscopy (FTIR) analysis indicated there were compatibilization reactions between the components. The miscibility and thermal behavior of the blends were investigated by dynamic mechanical analysis (DMA), differential scanning calorimetric (DSC), and thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were applied to observe the fractured surface and phase morphology to study the toughness mechanism. A typical core-shell morphology, ZrP wrapped by EMA-GMA phase, was observed in the nanocomposites, which can cause plastic deformations. The supertough effect of the compound was mainly confirmed by effective interfacial compatibilization and massive shear-yielding deformation achieved by the synergy of EMA-GMA with ZrP in the PLA matrix.

A promising screw-extrusion steam explosion pretreatment process: effects on the morphological and structural features of Eucalyptus woodchips

SESE pretreatment is a continuous high-efficiency process that dramatically decreases fiber size and breaks structural recalcitrance.

Effect of compatibilizer on the properties of PBS/lignin composites prepared via a vane extruder

Maleic anhydride (MAH) grafted polymers and silanes have been used as the compatibilizer in poly (butylene succinate)/lignin (PBS/lignin) composites. Compatibilized composites were fabricated by a novel vane extruder (VE). The effects of MAH grafted and coupling agent on the mechanical, thermal property, rheological property and water absorption of PBS/lignin were investigated. The results showed that the use of MAH grafted polymers and silanes resulted in significant improvements in flexural property, tensile modulus and tensile strength. Furthermore, MAH grafted polymers and silanes exhibited some improvement on the properties of vicat softening temperature as well as water absorption. The composites treated by MAH grafted polymers and silanes showed non-Newtonian behaviors from rheological tests. A better interfacial adhesion between lignin and matrix was observed from the scanning electron microscopy (SEM) of the compatibilized composites.

MgO nanowire growth from Mg metal and SiO2

Comparative study on the diameter distribution of MgO nanowires has been carried out. MgO nanowires could be synthesized by the direct reaction between metallic magnesium and silica, and the obtained nanowires have diameters ranging from 50 to 200 nm and lengths of several hundreds nanometers, exhibiting a straight wire. The diameter can be downscaled to smaller than 50 nm, and the nanowire exhibits a curved and twisted one-dimensional structure with lengths up to several micrometers, when a fine support catalyst was used as the reactant. The diameter-controlled growth mechanism was also explained in this work.

Circulating bioactive inhibin levels during human pregnancy

In this study bioactive inhibin was measured in 112 serum samples from 103 pregnant women by a sensitive ovine pituitary cell culture system. Human inhibin activities were detected in a range between 0.02-5.28 U/mL at six dilutions by using serum from the 38-week pregnant women as a quality control. A remarkable increase in serum inhibin was observed from 4 to 38 weeks of pregnancy. The mean serum inhibin level was 1.58 U/mL at 4 weeks. Thereafter, inhibin levels increased progressively with the weeks of pregnancy (r = 0.988; P less than 0.001). In the midterm of pregnancy, serum inhibin was elevated at average levels of 2.84 and 3.84 U/mL at 20 and 28 weeks, respectively. The peak level of inhibin (5.33 U/mL) was obtained at 38 weeks, which was an increase of 237% compared to that at 4 weeks. The average rate of increase in serum inhibin levels was 14.51% every 2-4 weeks (ranging from 8.1-20%). These findings suggest that circulating inhibin is useful marker during human pregnancy.