Low Degree Of Cross-linking Research Articles

Electrical Treeing Phenomena in Two-Layer Silicone Gel with Different Crosslinking Degrees and its Dielectric Strength

Silicone gel is widely used to encapsulate power modules, and improvement of its dielectric strength has been required. So, the purpose of our research is to improve dielectric strength of silicone gel encapsulant, and we focus on crosslinking degree of silicone gel. Previous studies have shown that growth mechanism of electrical tree changes with crosslinking degree of silicone gel. This suggests the possibility that the presence of the interface by different crosslinking degrees inhibits the tree growth. In this paper, we have investigated the tree growth and breakdown characteristics in silicone gel - crosslinking degrees graded layer materials. The interfaces in our study are arrange as being vertical to the line of electric force. Consequently, it was clarified that barrier effect of interface by different crosslinking degrees and the relaxation of electric field in low crosslinking degree region retards on tree growth, which improves the dielectric strength.

Synthesis and characterization of positive volume phase transition hydrogel membrane prepared using a cellulose substrate

ABSTRACT Thermo-responsive hydrogels display swell-collapse behavior in response to changing temperature. While the hydrogels themselves have many applications such as environmental and chemical separations, the hydrogel can be incorporated within a membrane substrate to improve its mechanical properties and expand the opportunities for development and implementation. The present work describes synthesis of positive volume transition temperature responsive poly(acrylamide-co-acrylic acid) hydrogels on cellulose paper substrates. Effects of factors including co-monomer ratios, degree of crosslinking and mass loading are assessed for Series A random copolymer hydrogels in terms of permeability response. Examination of the membranes is then extended to investigate inter-penetrating networks (IPN) between acrylamide and acrylic acid homo-polymer hydrogels. Series B membranes explore the impact of nonpolar ligands on temperature response through addition of butyl methacrylate co-monomer. For both random copolymer and IPN hydrogel membranes, mass loading dominates permeability performance, though certain criteria must be met. Performance of the Series A membranes was found to be ideal when monomer ratio was 1:1 and there was a lower degree of crosslinking. Addition of butyl methacrylate did not appear to have a consistent impact on the membrane response, appearing to be tied to the degree of crosslinking for random copolymer hydrogel coatings.

Improved viability of probiotics encapsulated in soybean protein isolate matrix microcapsules by coacervation and cross-linking modification

The objective of this research was to encapsulate probiotic bacteria based on soy protein isolate (SPI) matrix using either coacervation, cross-linking modification or their combination, and investigate the influences on the survival of probiotic bacteria during spray drying, in vitro gastrointestinal digestion, heating, UV irradiation and storage. A probiotic isolate Lactobacillus plantarum 550 was spray dried in SPI solution combined with either pectin (PEC), transglutaminase (TGase) or their combination. High survival rate and low moisture content were obtained for all the samples. Microcapsules fabricated using either SPI-PEC coacervation or TGase induced cross-linking obtained well cell survival during gastric digestion, heat/UV treatment and storage, however, combination of these two modification methods generated microcapsules with lower cross-linking degree and loose package structure corresponding with significant negative effects to the cell viability during gastric digestion and storage. Among the formulations tested, SPI-PEC microparticles provided the best protection to the probiotic cells, as pectin own well thermal stability and digestion resistibility, could fill the cracks and voids existed in SPI matrix and form hydrogen bond to stabilize cell membrane during processing. In conclusion, the current study demonstrated that SPI based probiotic microcapsules with high structural density and cross-linking degree may provide better protection to adverse external environment.

NIR-II live imaging study on the degradation pattern of collagen in the mouse model.

The degradation of collagen in different body parts is a critical point for designing collagen-based biomedical products. Here, three kinds of collagens labeled by second near-infrared (NIR-II) quantum dots (QDs), including collagen with low crosslinking degree (LC), middle crosslinking degree (MC) and high crosslinking degree (HC), were injected into the subcutaneous tissue, muscle and joints of the mouse model, respectively, in order to investigate the in vivo degradation pattern of collagen by NIR-II live imaging. The results of NIR-II imaging indicated that all tested collagens could be fully degraded after 35 days in the subcutaneous tissue, muscle and joints of the mouse model. However, the average degradation rate of subcutaneous tissue (k = 0.13) and muscle (k = 0.23) was slower than that of the joints (shoulder: k = 0.42, knee: k = 0.55). Specifically, the degradation rate of HC (k = 0.13) was slower than LC (k = 0.30) in muscle, while HC showed the fastest degradation rate in the shoulder and knee joints. In summary, NIR-II imaging could precisely identify the in vivo degradation rate of collagen. Moreover, the degradation rate of collagen was more closely related to the implanted body parts rather than the crosslinking degree of collagen, which was slower in the subcutaneous tissue and muscle compared to the joints in the mouse model.

Novel macrocyclic polyamines regulated nanofiltration membranes: Towards efficient micropollutants removal and molecular separation

The discharge of wastewater containing organic micropollutants not only causes severe environmental pollution, but also exacerbates the scarcity of freshwater resources and poses a serious threat to human health. The nanofiltration (NF) membrane has unique advantages and obvious energy-saving effects in the demineralization of organic micropollutants. Poly(piperazine) amide NF membrane exhibits the poor organic micropollutants/salt selectivity and low water permeance. Therefore, developing a novel NF membrane with high water permeance and superior selectivity is of significance. In this study, a loose nanofiltration (LNF) membrane is fabricated by interfacial polymerization with 1, 4, 7, 10-tetraazacyclododecane (Cyclen) as a new aqueous phase monomer to modulate the polyamide microstructure. The steric structure of Cyclen is larger than that of PIP, and the steric hindrance increases, resulting in a low stacking density of the formed polyamide polymer. Compared with the PIP-based NF membrane, the fabricated Cyclen-TMC LNF membrane has a smoother surface, a higher density of carboxyl groups, and a lower degree of cross-linking. The Cyclen-TMC membrane exhibits the considerable water permeance, with the corresponding rejection of 99.9% and 92.7% for methyl blue and tetracycline (pH = 9), respectively, while maintaining a low rejection for monovalent salts (e.g., 4.5% for NaCl). Furthermore, the LNF membrane shows a superior anti-fouling performance with the relatively smooth, highly negatively charged surface and low operation pressure. The novel LNF membrane exhibits a high potential for textile and pharmaceutical wastewater treatment. This study provides a new candidate to regulate the separation performance of NF membranes using new aqueous monomers.

Physicochemical properties and combustion characteristics of coal gasification fine ash modified by NaOH-HCl hydrothermal treatment

Coal gasification fine ash (CGFA) is difficult to handle, which makes its effective utilization difficult. This study modified a typical CGFA sample, referred to as dry ash (DA), by using a NaOH-HCl hydrothermal process and analyzed the physicochemical properties of the carbon residue after treatment. The evolution of the physicochemical properties and the effect of this evolution on the combustion characteristics of the sample were investigated in detail. It was determined that the loss on ignition (LOI) significantly increased after DA was subjected to NaOH-HCl hydrothermal treatment. The carbon skeleton of the residual carbon was also modified, with a higher degree of looseness and a lower degree of cross-linking. At the same time, the specific surface area of the carbon particles and the content of surface CC bonds increased. This was beneficial for improving the combustion reaction activity of the treated sample. It is worth noting that compared with DA, DA-NC (samples obtained after DA was hydrothermally treated with NaOH) exhibited an LOI increase of 27.98 %, an ash removal rate of 48.32 %, and an SBET as high as 354.09 m2/g. Proximate analysis and thermogravimetric analysis further showed that NaOH-HCl hydrothermal treatment effectively increased the residual carbon content of the sample and reduced the activation energy required for combustion. The comparable combustion characteristics of DA-N and DA-NC (samples obtained after DA was hydrothermally treated with NaOH-HCl) with coal demonstrated their value as fuels. This work demonstrates that DA can be successfully modified into high calorific value solid fuel by NaOH-HCl hydrothermal treatment, which is beneficial for realizing the large-scale resource processing of CGFA. Moreover, the evolution of the physical and chemical properties of the residual carbon during the treatment process leads to a significant improvement in combustion characteristics.

Cross-linking effects of EGCG on myofibrillar protein from common carp (Cyprinus carpio) and the action mechanism.

The cross-linking effects and action mechanism of epigallocatechin gallate (EGCG) on myofibrillar protein from common carp (Cyprinus carpio) were investigated. According to particle size, zeta potential, and atomic force microscopy, EGCG could cause the aggregation of myofibrillar protein, while hydrogen bonds and electrostatic interactions were the main molecular forces. With the measurement of Fourier transform infrared spectrum, surface hydrophobicity, fluorescence spectrum, circular dichroism spectrum, and molecular dynamics simulation, EGCG could make the spatial configuration of myofibrillar protein loose, enhance the exposure of amino acid residues, and further change its secondary and tertiary structures by forming intermolecular and intramolecular hydrogen bonds with myofibrillar protein. In addition, the gel properties of myofibrillar protein were improved by EGCG. All results suggested that EGCG had the cross-linking effects on myofibrillar protein in carp meat and could further improve its properties, which showed the potential to improve the qualities of fish meat in food industry. PRACTICAL APPLICATIONS: Compared with other meat, fish meat is particularly easy to break and deteriorate during its processing and sales due to the short length and low cross-linking degree of fish myofibrillar protein, which shows some negative impacts on the quality of fish meat. In the present study, epigallocatechin gallate (EGCG) showed the significant cross-linking effects on carp myofibrillar protein and further improved its physicochemical properties. All results suggested that EGCG had the potential to increase the cross-linking degree of fish myofibrillar protein and improve its properties, so as to ameliorate the quality of fish meat during processing and storage.

Imaging of the microstructure of Carbopol dispersions and correlation with their macroelasticity: A micro- and macrorheological study

We developed a new data analysis strategy, the so-called micro-rheo-mapping technique, based on multiparticle tracking experiments to obtain an accurate and direct visualization of the microstructure of commercial acrylate thickeners of Carbopol-type with high (Ultrez 10), intermediate (ETD 2020), and low (ETD 2050) degree of crosslinking. At low polymer concentration, aggregates made of several primary Carbopol particles are formed with an average diameter of 43 ± 11, 56 ± 14, and 10 ± 2.5 μm for Ultrez 10, ETD 2020, and ETD 2050, respectively. For ETD 2050, the least crosslinked thickener, the shell of dangling polymer chains covering the aggregate surface is thicker than for ETD 2020 and Ultrez 10. At technically relevant polymer concentrations, our results indicate, for all three thickeners, that the microstructure is highly heterogeneous with regions of different crosslink densities. One region inaccessible for tracer particles corresponding to a mixture of polydisperse aggregates and individual primary particles with a core mesh size less than 200 nm and a second, diluted enough to be accessible and which exhibits both elastic and viscous characteristics. The study of the impact of pH, polymer concentration, and crosslink density on these local structural and viscoelastic heterogeneities as well as macrorheological properties allowed us to establish a correlation between microstructure and macroelasticity. In particular, we found that the bulk shear modulus strongly depends on the fraction of inaccessible areas, making this microscopic parameter most relevant for describing the macroelasticity of Carbopol gels, whereas the local elasticity of the interstitial regions is of minor importance.

Dual Rolling Circle Amplification-Assisted Single-Particle Fluorescence Profiling of Exosome Heterogeneity for Discriminating Lung Adenocarcinoma from Pulmonary Nodules

Dual Rolling Circle Amplification-Assisted Single-Particle Fluorescence Profiling of Exosome Heterogeneity for Discriminating Lung Adenocarcinoma from Pulmonary Nodules

A Computer Simulation Study of Thermal and Mechanical Properties of Poly(Ionic Liquid)s.

Thermal and mechanical properties of poly(ionic liquid)s (PILs), an epoxidized ionic liquid-amine network, are studied via molecular dynamics simulations. The poly(ionic liquid)s are designed with two different ionic liquid monomers, 3-[2-(Oxiran-2-yl)ethyl]-1-{4-[(2-oxiran-2-yl)ethoxy]phenyl}imidazolium (EIM2) and 1-{4-[2-(Oxiran-2-yl)ethyl]phenyl}-3-{4-[2-(oxiran-2-yl)ethoxy]benzyl}imidazolium (EIM1), each of which is networked with tris(2-aminoethyl)amine, paired with different anions, bis(trifluoromethanesulfonyl)imide (TFSI−) and chloride (Cl−). We investigate how ionic liquid monomers with high ionic strength affect structures of the cross-linked polymer networks and their thermomechanical properties such as glass transition temperature (Tg) and elastic moduli, varying the degree of cross-linking. Strong electrostatic interactions between the cationic polymer backbone and anions build up their strong structures of which the strength depends on their molecular structures and anion size. As the anion size decreases from TFSI− to Cl−, both Tg and elastic moduli of the PIL increase due to stronger electrostatic interactions present between their ionic moieties, making it favorable for the PIL to organize with stronger bindings. Compared to the EIM2 monomer, the EIM1 monomers and TFSI− ions generate a PIL with higher Tg and elastic moduli. This attributes to the less flexible structure of the EIM1 monomer for the chain rotation, in which steric hindrance by ring moieties in the EIM1-based PIL enhances their structural rigidity. The - stacking structures between the rings are found to increase in EIM1-based PIL compared to the EIM2-based one, which becomes stronger with smaller Cl− ion rather than TFSI−. The effect of the degree of the cross-linking on thermal and mechanical properties is also examined. As the degree of cross-linking decreases from 100% to 60%, Tg also decreases by a factor of 10–20%, where the difference among the given PILs becomes decreased with a lower degree of cross-linking. Both the Young’s (E) and shear (G) moduli of all the PILs decrease with degree of cross-linking, which the reduction is more significant for the PIL generated with EIM2 monomers. Transport properties of anions in PILs are also studied. Anions are almost immobilized globally with very small structural fluctuations, in which Cl− presents lower diffusivity by a factor of ~2 compared to TFSI− due to their stronger binding to the cationic polymer backbone.

One-Step Synthesis of Cross-Linked Esterified Starch and Its Properties

Cross-linked esterified starch (CES) was prepared using a one-step method, where maize starch was selected as the raw material, sodium trimetaphosphate as the cross-linking agent, and acetic anhydride as the esterifying agent, respectively. A response surface experiment was systematically conducted for analyzing the correlation of the experimental variables (cross-linked temperature, pH, reaction time, sodium trimetaphosphate and acetic anhydride dosage) and properties of the product (peak and final viscosity). The Brabender viscosity, freeze-thaw stability, shearing resistance, and acid tolerance of the cross-linked acetylated dual modified starch were studied under different conditions of crosslinking degree and acetyl content. Meanwhile, the granular structure and morphology of the modified starch were analyzed. The results indicated that: after cross-linked acetylated dual modification, the starch had a distinct birefringence and granular structure, along with the creation of new carbonyl groups. The low degree of crosslinking and high acetyl contents were beneficial to the viscosity, which was significantly increased at both low and high temperatures. Moreover, the freeze-thaw stability of CES was elevated sharply after five cycles. In addition, CES displayed increased shear and acid tolerance compared to the original waxy maize, and their lowest differences between waxy maize and CES were only 0.62% and 0.59%, respectively. In summary, a novel method for starch modification was provided, and the synthesized CES was suggested to have exceptional performance for the food industry.

Molecular dynamics study on mechanical properties of helical graphenes/epoxy nanocomposites

Helical graphenes (HGs) have attracted much attention due to its excellent electrical and mechanical properties, and provide an ideal nanofiller for the preparation of novel functional epoxy resin matrix composites.The mechanical properties of HGs/epoxy resin composites (marked as HGs/epoxy) are investigated by molecular dynamics (MD) simulations and compared with those of pure epoxy resin systems (referred to as epoxy).The results show that HGs/epoxy systems have higher Young's modulus and yield strength than pure epoxy systems with the same crosslinking degree.Interestingly, the strengthening effect of HGs on the epoxy systems with low crosslinking degree is more obvious. The Young's modulus of the HGs/epoxy system with 40% crosslinking degree increase by 55.73%, 53.82% and 48.61% along the X, Y, Z directions, respectively.For the HGs/epoxy system with 60% crosslinking degree, the yield strengths increase by 36.64%, 26.69% and 43.39% along three directions, respectively. The enhancement of the overall mechanical properties for the HGs/epoxy systems is mainly attributed to the entanglement between molecular chains and HGs. Especially when the molecular chains are wound around adjacent coils of HGs,the binding energy between the matrix and reinforcement is greater,and the system exhibits better mechanical properties and more obvious mechanical anisotropy.These results provide the theoretical support for the preparation of novel epoxy resin matrix composites.

Mechanical property and dielectric spectra analysis of solvent-free poly(ionic liquid)/poly(ethyl acrylate) double network elastomers under tensile deformation

Solvent-free double network elastomers have excellent mechanical properties and stability. However, there are few studies on ion transport in solvent-free double network elastomers. In this paper, we prepared a kind of poly(ionic liquid) (PIL)-based solvent-free elastomer with double network structure by using crosslinked poly[2-(methacryloyloxy)ethyl] trimethyl ammonium bis(trifluoromethanesulfonyl) imine (P[VBTMA][TFSI]) network as brittle network and crosslinked poly(ethyl acrylate) (PEA) as stretchable network. The mechanical properties and the ion transport of samples as a function of elongation strain were investigated by stress-strain curves and broadband dielectric spectroscopy, respectively. The results show the double network elastomer has medium elastic modulus of 0.4–0.9 MPa, high elongation strain of 1700–2300% and ionic conductivity of 1.04 × 10−7 S·m−1 at room temperature. When the sample does not yield, stretching almost does not affect the ion transport in the network. As the strain exceeds the yield point, the conductivity relaxation time of the samples with low crosslinking degree of PIL network increases little, while the conductivity relaxation time of the samples with high crosslinking degree increases significantly. This is because the former network breaks uniformly, while the latter appears phase separation when yielding. The result improves the understanding of ion transport in double network polyelectrolyte elastomers.

Selective recovery of lithium from spent coin cell cathode leachates using ion imprinted blended chitosan microfibers: Pilot scale studies provide insights on scalability

We report an approach on specific and scalable recovery of lithium ions from coin cells using functionalized chitosan microfibers. Low swelling ratios and high degree of crosslinking resulted from a dual combination of blended viscosities and crosslinking. Owing to their defined structure (pore diameter: 2.29±0.31 µm; fiber diameter: 176.5±3.44 µm; ion exchange capacity: 8.45 meq/g), imprinted microfibers exhibited high lithium uptake potential (100 mg/g), high distribution coefficient (6969.7 mL/g) and high separation factors (90) in a multi-metal system generated from leachates (co-ions: Co(II), Ag(I), Mn(II), Cu(II), Al(III), Ni(II), Na(I), K(I) and Ca(II)). The uptake phenomena followed a homogeneous monolayer adsorption mode and a spontaneous endothermic nature (ΔG:-20.3 KJ/mol). High values of relative lithium sorbed (RLS) (>20) and relative lithium released (RLR) (>9) in case of imprinted microfibers suggested high selectivity. Batch conditions showed a selective recovery of 45.7%/g/L of leachates (< 50 cathodes) at pH of 6.1. However, packed bed column studies showed that 14.3 g of biosorbent could recover up to 99.1% lithium (recovered lithium of up to 971.19 mg/L) over 9 cycles (250 cathodes; CoLi: 976.33 mg/L). The present study suggested blended and imprinted chitosan microfibers as a useful matrix towards scalable lithium recovery.

Carbon nanomaterials as additives to ethylene vinyl acetate copolymer foams for sport footwear applications

AbstractEthylene vinyl acetate (EVA) copolymer foams with addition of 1.0, 2.5, and 5 wt% of carbon nanomaterials (graphene, graphene oxide, carbon nanotubes, and multiwalled carbon nanotubes) were fabricated. Properties of these foams were compared with reference sample (no additives) and samples containing carbon black. The following properties of these samples were examined: density, compressive stress (50% compression), impact behavior, thermal conductivity, and hydrophobicity. The morphology was studied using scanning electron microscopy. The samples were additionally characterized using thermal gravimetric analysis and differential scanning calorimetry. Increasing weight percentage of carbon‐based additives led to foam structure with lower porosity and higher density. Samples with a higher degree of cross‐linking were less dense (~10%) as compared to the reference sample and also displayed better mechanical and thermal properties. Increasing weight percentages of additives led to higher compressive strength and higher energy absorption. Samples with 5 wt% of additives and increased quantity of cross‐linking agent exhibited great mechanical properties. Despite their lower density, these samples had higher values of compressive stress, 10%–15% higher than those of the reference sample, and higher energy return properties. All samples follow the trend of increasing values of compressive strength with the increase in density, for some samples, this correlation has quasi linear character. The obtained results show that EVA foams with the addition of carbon black, graphene, carbon nanotubes, and multiwalled carbon nanotubes have properties desirable in high‐performance materials for sport footwear soles. Multiwalled carbon nanotube additives could be incorporated at low weight percentages and low degree of crosslinking into EVA matrix to achieve lower density and enhanced energy repulsion and cushioning effects.

Silica–Polystyrene Hybrid Core/Shell Microparticles of Rhodium–Chiral Diene Complexes as Catalysts for Asymmetric 1,4-Addition Reactions

Heterogeneous catalysts for fine chemical synthesis play a crucial role in establishing an efficient chemical process. Immobilization of homogeneous catalysts is an important method for the preparation of heterogeneous catalysts; however, it is often accompanied by a loss of catalytic activity due to limited mass transport in the support matrix. Here, we have designed core/shell type polystyrene shell supports on silica with low degrees of cross-linking to improve accessibility to reaction sites. It was found that rhodium–chiral diene complexes on core/shell particles showed higher catalytic activity in comparison those on conventional supports and even better catalytic activity than the corresponding homogeneous catalyst in asymmetric 1,4-addition reactions. Our results may provide a general strategy to obtain many other heterogeneous catalysts with high activities.

Preparation of liquid crystal-based molecularly imprinted monolith and its molecular recognition thermodynamics

液晶分子印迹聚合物(MIPs)因刚性液晶单体的加入而在超低交联度水平下也能印迹和识别模板分子,有效解决了传统MIPs因高交联度造成的位点包埋、结合容量低、传质慢等问题。尽管液晶MIPs具有如此独特的优势,但却面临着由于交联度的大幅度降低而导致印迹效果下降的问题。为了研究液晶MIPs的结合特性,制备具有良好印迹效果的低交联液晶MIPs,该文通过二次接枝聚合,制备了一系列不同交联度的液晶分子印迹整体柱,用高效液相色谱法研究了聚合参数与印迹整体柱亲和性的关系。实验中选用三羟甲基丙烷三甲基丙烯酸酯(TRIM)为交联剂,以甲苯和十二醇为致孔剂合成整体柱骨架,并在此基础上以(S)-萘普生为模板,加入液晶单体4-氰基苯基单环己基乙烯(CPCE)进行二次聚合接枝。实验中系统考察了流动相中乙腈比例及缓冲液pH值对色谱保留的影响,结果发现液晶单体的加入使得MIPs对萘普生保留控制机制由原来的氢键作用变为了疏水作用;通过动态吸附实验得到的突破曲线经前沿分析及对吸附等温线Langmuir、Freundlich和Scatchard分析拟合,发现交联度为15%时液晶MIPs印迹因子最大(3.78)、非均一性最强,且特异性吸附量高于非特异性吸附量。液晶MIPs的计量置换模型(SDM-R)分析表明,液晶印迹整体柱对模板分子的总亲和力(ln A=0.645)明显高于其类似物;而从空间匹配程度看,与液晶印迹整体柱空间匹配程度最高的是酮洛芬而非模板分子,但液晶印迹整体柱对酮洛芬的总亲和力(ln A=0.242)不及模板分子的一半,表明在本低交联液晶印迹系统中,空间效应不是决定印迹系统识别能力的主要因素。进一步的分离热力学研究发现,低交联液晶印迹柱的|ΔΔH|<T|ΔΔS|,而交联度为70%的非液晶MIPs柱的|ΔΔH|>T|ΔΔS|,表明液晶MIPs的分离过程是一个熵控制过程,而常规无液晶MIPs的分离过程是一个焓控制过程。上述结果表明,液晶单体的加入改变了MIPs的识别机制,适当的低交联度可显著提高液晶MIPs的识别性能,因此液晶MIPs这些特质有望使其成为新一代的MIPs。

Preparation and characterization of CeO2@high silica ZSM-5 inorganic-organic hybrid polyamide nanofiltration membrane

Nanofiltration with high stable permeance is of great significance for wastewater treatment. Herein, we reported the novel polyamide thin-film composite (PA TFC) nanofiltration membranes prepared for the first time by blending nanometer cerium doped high silica ZSM-5 zeolites (CeO2@HSZSM-5, CHZ) in the aqueous phase followed by the classic interfacial polycondensation. The structural morphology of these membranes and their performance had been characterized. SEM and XPS characterizations clearly revealed the presence of inorganic CHZ in the PA layer. The results also showed that the CHZ-integrated inorganic-organic PA TFC membranes with a higher fraction of CHZ had a thinner PA active layer (28.3 ± 3.6 nm) and slightly enlarged pore size with lower crosslinking degree. The optimized membranes exhibited 1.65-folds pure water permeability of the traditional membrane, 20.3 L/(m2.h.bar) with comparable Na2SO4 and MgSO4 rejection of 95.8% and 91.1%, respectively. The rejection of dyes stayed stable above 96.0% with boosted permeance, and the membrane almost completely removed CR and RB as well as natural organic matters. The composite membrane also sustained superior stability and excellent antifouling performance. The as-prepared CHZ-integrated PA TFC membranes with regulatable structural morphology and superior separation properties enables the potential practical application in wastewater treatment.

MicroRNA-activated hydrogel scaffold generated by 3D printing accelerates bone regeneration

Bone defects remain a major threat to human health and bone tissue regeneration has become a prominent clinical demand worldwide. The combination of microRNA (miRNA) therapy with 3D printed scaffolds has always posed a challenge. It can mimic physiological bone healing processes, in which a biodegradable scaffold is gradually replaced by neo-tissue, and the sustained release of miRNA plays a vital role in creating an optimal osteogenic microenvironment, thus achieving promising bone repair outcomes. However, the balance between two key factors - scaffold degradation behavior and miRNA release profile - on osteogenesis and bone formation is still poorly understood. Herein, we construct a series of miRNA-activated hydrogel scaffolds (MAHSs) generated by 3D printing with different crosslinking degree to screened the interplay between scaffold degradation and miRNA release in the osteoinduction activity both in vitro and in vivo. Although MAHSs with a lower crosslinking degree (MAHS-0 and MAHS-0.25) released a higher amount of miR-29b in a sustained release profile, they degraded too fast to provide prolonged support for cell and tissue ingrowth. On the contrary, although the slow degradation of MAHSs with a higher crosslinking degree (MAHS-1 and MAHS-2.5) led to insufficient release of miR-29b, their adaptable degradation rate endowed them with more efficient osteoinductive behavior over the long term. MAHS-1 gave the most well-matched degradation rate and miR-29b release characteristics and was identified as the preferred MAHSs for accelerated bone regeneration. This study suggests that the bio-adaptable balance between scaffold degradation behavior and bioactive factors release profile plays a critical role in bone regeneration. These findings will provide a valuable reference about designing miRNAs as well as other bioactive molecules activated scaffold for tissue regeneration.

The stability of paintings and the molecular structure of the oil paint polymeric network

A molecular-level understanding of the structure of the polymeric network formed upon the curing of air-drying artists’ oil paints still represents a challenge. In this study we used a set of analytical methodologies classically employed for the characterisation of a paint film—based on infrared spectroscopy and mass spectrometry—in combination with solid state NMR (SSNMR), to characterise model paint layers which present different behaviours towards surface cleaning with water, a commonly applied procedure in art conservation. The study demonstrates, with the fundamental contribution of SSNMR, a relationship between the painting stability and the chemical structure of the polymeric network. In particular, it is demonstrated for the first time that a low degree of cross-linking in combination with a high degree of oxidation of the polymeric network render the oil paint layer sensitive to water.