最新刊期
- 摘要：Organic electrochemical transistors play a crucial role in modulating the electronic structure and conductivity of conjugated films through ion-electron coupling, making them highly promising for the advancement of flexible smart electronics. This article provides a comprehensive overview of the organic electrochemical transistors by integrating electrochemical doping principle. It discusses the recent advancements in ion-electron coupling performance and mechanical characteristics such as stretchability, mechanical conformability, and bioviscosity. In addition, it reviews the multifunctional applications of the organic electrochemical transistors, including their role in complementary logic circuits, biosensing, and bionic neural synapses. Furthermore, emphasis is placed on research strategies aimed at enhancing device performance and enabling multifunctionality through approaches like organic conjugated molecule design, interface modification, ion dynamics control, and device structure optimization, underscoring the versatility of OECTs in smart electronics. Finally, the key challenges and opportunities of organic electrochemical transistors are discussed in detail concerning integrated intelligent sensing devices for sensing-adaptation-feedback-processing and low-cost commercial preparation.关键词：Organic electrochemical transistor;Conjugated molecules;Electric performance;Mechanical properties;Multifunctional application
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发布时间：2024-05-18 - 摘要：A regioselectively substituted cellulose derivative with bulky pendants at the 6-position, that is the cellulose-[2,3-(3,5-dimethyl)-6-(4-(4-(3-(9-ethyl-9H-carbazole-3)ureido)benzyl))]phenylcarbamate (Cel-1), was successfully synthesized using cellulose as substrate by 6-position-protection method and carbamoylation. The 1H-NMR spectrum and elemental analysis data indicated that the cellulose derivative was structurally regular with almost complete substitution as expected. The fluorescent recognition property of Cel-1 was then evaluated in detail based on twelve metal ions. The results indicated that the bulky cellulose derivative (Cel-1) could realize excellent dual-mode recognition to both Fe3+ and Cu2+ with high sensitivity and high selectivity in the DMSO/H2O system, together with high anti-counterfeiting ability to the other ten metal ions tested in the study. Especially, the limits of detection of Cel-1 for Fe3+ and Cu2+ in both fluorescence and UV-visible modes were lower than the maximum acceptable concentrations of the two ions in drinking water as defined by the United States Environmental Protection Agency (EPA). It demonstrated that the obtained bulky cellulose derivative possessed high-efficient and specific fluorescent recognition ability for Fe3+ and Cu2+, which could be used as chemosensors for the rapid recognition and detection of the two metal ions. In addition, the fluorescent ink prepared based on Cel-1 could not be observed under natural light, whereas emitted bright blue fluorescence under ultraviolet light, suggesting its potential in the anti-counterfeiting related field.关键词：Fluorescent sensing;Bulky pendants;Cellulose derivatives;Metal ion recognition;Dual mode detection
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发布时间：2024-05-17 - 摘要：This study focuses on the development of a sustainable and highly sensitive Antheraea pernyi (A. pernyi) silk paper-based electrochemical sensor, utilizing the excellent solvent resistance of silk paper as the substrate and incorporating molybdenum disulfide (MoS2) functional units. The electrochemical sensing principle of this sensor is based on a transpiration-driven electricity generation mechanism. Different solvents interact distinctly with the sensor, resulting in transpiration-driven electrical signals with varying characteristics. Although these electrical signals display complex band-shaped patterns lacking sharp peaks or specific mutation points, they exhibit highly reproducible trends for specific solvent systems. Consequently, this study further employs a feedforward neural network to construct a solvent identification model based on the oak silk fibroin ultrafine paper electrochemical sensor. This model processes and analyzes these complex yet highly repetitive electrical signals. The AI-driven A. pernyi silk paper-based electrochemical sensor not only accurately identifies solvents with highly similar chemical structures and properties, such as methanol, ethanol, isopropanol, and deionized water, but also recognizes chemically similar mixed solvent systems, like varying proportions of ethanol-water mixtures. In 100 identification tests, the accuracy was 100%. The development of this AI-driven A. pernyi silk paper-based electrochemical sensor offers a convenient, cost-effective method for rapid and accurate solvent detection, holding significant implications in fields such as alcohol testing, environmental monitoring, and chemical analysis.关键词：Silk paper;Eutectic solvent;Depolymerization;Electrochemical sensor;Deep learning
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发布时间：2024-05-17 - 摘要：Form-stable phase change materials (FSPCMs) are a kind of latent heat/cold energy storage materials and play key role in fields like new energy development, cold chain temperature control and healthcare. Lots of expensive chemicals have been investigated as phase change materials (PCMs) for FSPCMs, however, the application of water, a very cheap and abondance material in our planet, as a phase change cold energy storage material for FSPCMs is neglected. Herein, a kind of hydrogel based on poly(vinyl alcohol) and poly(acrylic acid) was prepared at first, and then novel FSPCMs with high latent cold energy storage capacity were obtained by solving the problem of water leakage in the hydrogel through simple surface freeze drying. The latent cold energy storage capacity of the obtained hydrogel-based FSPCMs attained 237 J/g, and the water in the FSPCMs would not volatilize when the temperature was not higher than 50 ℃. The FSPCMs also exhibited excellent anti-leakage performance even it was heavily pressed. Meanwhile, the FSPCMs possessed good long-term thermal reliability and its latent cold storage performance has not changed after 50 freeze-thaw cycles. The FSPCMs also had good temperature control and shaping properties, making it applicable to cold storage, cold chain temperature control, cold compress and other fields. In addition, in order to fully utilize the high porosity of dried hydrogel, exfoliated graphite nanoplatelets (xGnP) were applied to enhance the stability of the hydrogel skeleton with the largest water content, and a novel supporting material with high porosity was obtained by freeze-drying. Then, erythritol (ET) and PEG2000, two water-soluble PCMs, were selected as representatives, and two types of FSPCMs were prepared by melting impregnation. Both types of FSPCMs possessed very high content of PCMs and very high latent heat storage capacity, which proved that polymer network skeletons of hydrogels were perfect supporting materials for FSPCMs. Consequently, the results obtained in this study have important value for promoting the application of hydrogel itself and hydrogel materials in the fields of heat energy storage and temperature control.关键词：Hydrogel;Form-stable phase change materials;Phase change temperature control;Cold storage;Supporting materials
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发布时间：2024-05-17 - 摘要：A series of large-ring metal coordination catalysts with manganese(Ⅲ) as the axial ligand and alkali metal(Ⅰ) as the core were synthesized in this experiment, and their structures were characterized in detail by matrix assisted laser desorption time-of-flight mass spectrometer (MALDI-TOF-MS) and elemental analysis. These catalysts can catalyze the polymerization of propylene glycolide (LA) and ε-caprolactone (ε-CL) in the presence of cyclohexane oxide (CHO). We screened and optimized different alkali metal ions to ensure the best polymerization performance. The experimental results show that the introduction of alkali metal centers significantly improves the performance of the catalysts, far exceeding that of mononuclear Schiff base manganese catalysts. The steric hindrance effect of the amine bridge moiety of the catalyst on the reaction activity is also significant. We investigated the stereo-selectivity of the catalysts for monomers and conducted copolymerization studies using different LA isomers, finding that this catalyst is more prone to obtaining polymers with isotactic tendencies. The polymerization mechanism was further analyzed by using MALDI-TOF-MS spectrometer to analyze the end groups of the obtained PLA and assist in the study of the polymerization mechanism. Experimental studies show that the stereo-selectivity of the polymerization is achieved through a chain-end control mechanism.关键词：Heterodinuclear complex;Polylactic;Polycaprolactone;Ring-opening polymerization;Non-homogeneous catalysts
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发布时间：2024-05-17 - 摘要：Based on polymerized thermally activated delayed fluorescence (TADF) small molecules, a series of single white-emitting polymers named P010-P075 have been designed and synthesized by using acridine- benzophenone-carbazole (AcBPCz) as the sky-blue TADF moiety, acridine-naphthalimide-carbazole (AcNICz) as the orange TADF moiety and tetramethylbenzene as the linker between them. After a modulation of the AcNICz content in the range of 1%-7.5%, a part energy transfer can happen from AcBPCz to AcNICz. Consequently, P010-P075 all display a dual spectral profile in the photoluminescence (PL): the sky-blue emission peaked at 482-492 nm is from AcBPCz, while the orange emission peaked at 590-602 nm is from AcNICz. And the ratio of sky-blue to orange emission together is found to be decreased gradually with the increasing content of AcNICz. The corresponding solution-processed OLEDs achieve a bright white electroluminescence (EL), revealing a maximum current efficiency of 5.4-16.8 cd·A-1 and a maximum external quantum efficiency of 3.0%-6.4%. Noticeably, the EL is obviously dependent on the AcNICz content, consistent with the PL counterparts. Ongoing from P010 to P075, the Commission Internationale d'Eclairage (CIE) coordinates are shifted from (0.32, 0.50) to (0.47, 0.44) and the correlated color temperature (CCT) is reduced from 5910 K to 2797 K. The obtained cold white EL for P010 and warm white EL for P075 are believed to be applicable for different lighting scenes.关键词：OLED;Thermally activated delayed fluorescence polymers;Single white-emitting polymers;Polymerized thermally activated delayed fluorescence small molecules;Emissive color
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发布时间：2024-05-17 - 摘要：The self-consistent field theory (SCFT) is employed to study the self-assembly behavior of AB diblock copolymers confined in alternately adsorbed nanopores. Focusing on the emergence and stability of the disk (Dk) phases, a series of phase diagrams are constructed with respect to the alternating adsorption period (w), size of the cylindrical pore (D), and the volume fraction of the A block (f). The results indicate a significant enhanced stability of Dk structure by the alternately adsorbing surface fields. The Dk structure is especially favored, when the alternating adsorption period is around 5.0Rg. With fixed w = 5.0Rg, the appearance of the Dk structure is tuned by D and f, it forms biconcave shape with negative curvatures within a certain varying ranges of D and f, otherwise it transforms into ellipsoidal or toroid shapes. Additionally, a number of novel cylinders and regularly arranged spheres emerged in the nanopores with specific surface fields. The results deepen the understanding of self-assembly behavior of block copolymers under cylindrical confinements, and provide theoretical guidance for the experimental preparation of such complex structures.关键词：Block copolymers;Self-assembly;Cylindrical confinement;Surface field induction;Self-consistent field theory (SCFT)
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发布时间：2024-05-17 - 摘要：As a main-chain liquid crystalline polyelectrolyte, poly(2,2'-disulfonyl-4,4'-benzidine terephthalamide) (PBDT) is characterized by its fully aromatic architecture, ultra-high density of sulfonate groups, intramolecular and intermolecular hydrogen bond networks formed by the amide groups. Here we describe a series of distinctive characteristics of PBDT solutions, including the self-assembled double helical conformations, formation of nematic liquid crystalline phases, and anisotropic ion transport along polymer chains. Based on the multi-scale molecular conformation of PBDT and its selective ion transport properties, composite materials with various functions can be designed, such as PBDT-based hydrogels, ionogels and nanocomposites. By emphasizing the rigid rod architecture and the anisotropic ion transport mechanism of counter ions in PBDT, the applications of PBDT composites in solid-state electrolytes and lithium battery electrode binders have been highlighted; meanwhile, indicating potential significance for the development of other rigid-rod polyelectrolyte materials similar as PBDT for the field of new energy storage and conversion and other related areas.关键词：Rigid rod polyelectrolytes;Double helical conformation;Liquid crystalline phase;Anisotropic ion transportation;Lithium batteries
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发布时间：2024-05-14 - 摘要：To investigate the effective procedure for controlled polymer structure and thermal properties through radical polymerization, amylose derivatives were used as chiral additives to induce the radical polymerization of methyl methacrylate (MMA). The effect of amylose derivatives on the structure and thermal properties of polymethylmethacrylate (PMMA) was subsequently explored. Four kinds of amylose derivatives were synthesized through carbamoylation, including amylose tri(4-chlorophenyl carbamate) (ACPC), amylose tri(phenylcarbamate) (ATPC), amylose tri(4-methylphenylcarbamate) (AMPC) and amylose tri(S-(-)-α-methylbenzyl carbamate) (ASMBC). The structures and degree of substitution of the amylose derivatives were characterized by magnetic resonance spectroscopy (1H-NMR) and circular dichroism (CD) spectra, demonstrating complete substitution and regular chiral helical structure of the obtained derivatives. The thermal stability of PMMA was assessed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), revealing a significant enhancement in the thermal stability of PMMA induced by amylose derivatives. Furthermore, the substituents properties of the derivatives and the polarity of the polymerization solvent significantly influenced the radical polymerization behavior of MMA. Both bulk polymerization and solution polymerization were effective in improving the thermal properties of PMMA, with the solution polymerization system utilizing non-polar octane as the solvent achieving the most significant improvement. Among the amylose derivatives, the para-methyl-substituted amylose derivatives (AMPC) demonstrated the most effective induction effect, which could increase the glass transition temperature (Tg) and the onset decomposition temperature (T0) of PMMA by 26 and 71 ℃, respectively. The induction mechanism of amylose derivatives was investigated using gel permeation chromatography (GPC), dynamic laser light scattering (DLS) and X-ray diffraction (XRD). The results indicated that MMA monomers could be arranged in order along the chiral helical cavity of the derivatives. This ordered arrangement can not only improve the structure order of polymer molecular chains, but also have a positive effect on its aggregation behavior, thereby achieving effective control of the thermal properties of PMMA. It suggests that the radical polymerization behavior and thermal properties of MMA can be effectively regulated by selecting appropriate helical polymers, offering a novel idea for exploring the controlled radical polymerization method of methacrylate monomers.关键词：Amylose derivatives;Polymethyl methacrylate;Thermal stability;Free radical polymerization
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发布时间：2024-05-13 - 摘要：The aramid fiber reinforced polyurethane composites (AF@PU), which exhibit high strength and lightweight characteristics, have attracted widespread concerns for advanced personal protective systems. However, the interface has consistently been the scientific issue that permeates composite research and is frequently overlooked. In this work, polydopamine and γ-aminopropyltriethoxysilane modified SiO2 (m-SiO2) were used to optimize the interfacial properties, and the effects on ballistic performance and ballistic damage mechanism of composites were deeply investigated. Attributing to the strong bonding strength between fibers and polymer resins improved by them at the interface, the interfacial peeling strength of m-SiO2/PDA/AF@PU is increased by 244.1% (4.68 N/cm); the interlaminar shear strength is increased by 30.7% (6.09 MPa); the tensile, flexural and compressive strength of is maximally increased by 5.0%, 91.4% and 69.5%, respectively. Notably, because the introduction of abundant m-SiO2 enhances the interface roughness, m-SiO2/PDA/AF@PU demonstrates the maximal energy absorption value; the ballistic limit velocity is improved from 449.8 m/s of AF@PU to 481.9 m/s of m-SiO2/PDA/AF@PU. This work highlights the optimization of interfacial properties and provides an efficient guideline for the design of next-generation fiber reinforced polymer resin composites.关键词：Composites;Interfacial modification;Polydopamine;Nano silica;Ballistic performance
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发布时间：2024-05-13 - 摘要：This study reported that an efficient and controllable ring-opening polymerization of ω‑Pentadecalactone (PDL) by using cyclic trimeric phosphazene base (CTPB) as a catalyst and benzyl alcohol (BnOH) as an initiator. High molecular weight PPDL was obtained after optimizing the experimental conditions. The PPDL film with high molecular weight not only showed similar mechanical properties, crystallinity and high melting point (Tm=95.5 ℃) as polyethylene, but also exhibited the degradability of aliphatic polyesters. Differential scanning calorimetry (DSC) proved that PPDL had good crystallinity. Wide-Angle X-ray Scattering (WAXS) showed that PPDL had a unit cell structure similar to that of commercial high-density polyethylene (HDPE). Moreover, bishydroxyl-end-capped PPDL (PPDL-diol) can be easily prepared via ROP of PDL with BDM as initiator. Then the PPDLs with high molecular weights were obtained by chain extension reactions with diisocyanates and showed enhanced mechanical properties. In addition, we synthesized a variety of random copolymers with different ratios of PDL and ε-caprolactone (ε-CL). The melting points and hydrolysis of the copolymers could be adjusted by changing the ratio of ε-CL. The melting points of the obtained random copolymers could be adjusted in the range of 53.0-95.5 ℃ by changing the ratio of ε-CL. Finally, the hydrolysis of PPDL copolyester was achieved under alkaline conditions. Compared with PPDL homopolymer, the hydrolysis of random copolymers showed faster hydrolysis rate and adjustability.关键词：Ring-opening polymerization;Organobase;Polyethylene-like polymers;Degradable polyester
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发布时间：2024-05-13 - 摘要：Porous polymers with azobenzene skeleton (Azo-POPs), which are characterized by good chemical stability, high specific surface area, and easy functionalization and modification, have shown great application prospects in a number of fields and attracted much attention. In this review, we firstly sorted out the ways of introducing azobenzene structural elements into porous polymer skeletons in recent years, including the condensation polymerization of polyaminoaromatics and poly(nitroso)aromatics, the oxidative coupling polymerization of polyaminoaromatics, the reductive coupling polymerization of poly(nitroso)aromatics and the coupling polymerization of electron-rich aromatics with polydiazonium salts, etc. It is pointed out that the coupling polymerization of electron-rich aromatic hydrocarbons with polydiazonium salts has mild conditions, high polymerization efficiency and good functional group tolerance. This paper briefly describes the examples and characteristics of functional Azo-POPs. The electron cloud, polar dipole interactions and alkalinity provided by amino or hydroxyl groups in Azo-POPs, can significantly improve the adsorption capacity of porous polymers for metal ions, polar compounds and CO2. Then the paper analyzes and demonstrates the irreversible isomerization of tris(β-hydroxyazo)benzene structure to tris(β-keto-hydrazone)cyclohexane structure, and analyzes and summarizes the applications of Azo-POPs in the fields of gas and vapor adsorption and storage, multiphase catalysis, removal of pollutants in water, gas membrane separation and electrochemistry. Finally, the challenges to the development of Azo-POPs are analyzed and pointed out, and the future development direction and prospect of Azo-POPs are discussed in the light of the existing research reports.关键词：Porous organic polymers;Azo-benzene;Hydroxyl-azobenzene;Amino-azobenzene;Tris(β-keto-hydrozo)cyclohexane
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发布时间：2024-05-11 - 摘要：The self-assembly behavior of three regio-isomers, namely the ortho-, meta-, and para-isomers, formed by double chains grafted at different vertices of cage-like molecules, was simulated using the dissipative particle dynamics (DPD) method. The results indicate that a long the varying length of the grafting chains the three regio- isomers exhibit inconsistent regulation of the emergence and stability of self-assembled structures. Specifically, when the grafting chains are relatively short, the curvature of the ordered structures self-assembled by the tail chains increases in the order of ortho-, meta-, and para-isomer. In contrast, when the grafting chains are longer, the cage-like molecules in different isomers tend to stack into distinct bicontinuous structures. The simulation results also predict that the temperature of the order-disorder transition (TODT) for the three regio-isomers decreases in the order of ortho-, meta-, and para-, and this trend is consistent with the TODT of the combined regio-isomers. The diverse phase behaviors in the regio-isomers can be understood from the different conformation of the chains and packing of the cage molecules. This study clarifies that the tiny differences in the structural unit can profoundly impact the self-assembled structures, which offers new insights into exploring unconventional order structures self-assembled in soft matters.关键词：Cage-like molecule;Block copolymer;Dissipative particle dynamics (DPD);Self-assembly
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发布时间：2024-05-11 - 摘要：It is a desirable method to develop high energy density supercapacitors without sacrificing power density to prepare electrode materials with both capacitance and battery characteristics by the modification of conductive conjugated polymers. In this study, the intermolecular force is strengthened by electron-withdrawing groups to improve the charge transfer performance of materials, improve the cyclic stability of electrode materials and make them have higher energy density and power density. We use liquid-phase treatment to treat CC and in situ oxidation polymerization to polymerize three D-A type conductive conjugated polymers on the surface of CC with 2,3-dichloro-5,6-dicyano-p-benzoquinone as the acceptor and 3,3-dimethylbenzidine, 3,3-dimethoxybenzidine and 3,3-dihydroxybenzidine as the donors. We studied the capacitance characteristics of three flexible composite electrodes. The P2/CC electrode material with a donor end of 3,3-dimethoxybenzidine exhibits fast electrochemical kinetics characteristics in the range of less than 70 mV·s-1, its discharge specific capacitance reaches 686.27 F·g-1 at a current density of 0.5 A·g-1, and the retention rate of the specific capacitance after 5000 charge discharge cycles is 99.70%. The composite electrode also achieved an energy density of 50.66 Wh·kg-1 at an ultra-high power density of 497.46 W·kg-1. The organic-inorganic synergistic effect between conductive conjugated polymers and CC helps to improve the conductivity and stability of electrodes, and the pseudocapacitive charge storage behavior of conductive conjugated polymers enhances the discharge specific capacity. The preparation of flexible composite electrodes provides a favorable reference for the low-cost development of new electrode materials with high energy density and power density to further improve the performance of supercapacitors.关键词：D-A type conductive polymer;Carbon cloth;Flexible electrodes;High energy density;High power density
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发布时间：2024-05-11 - 摘要：Sulfur dispersion is the most common crosslinking agent for latex vulcanization. However, sulfur dispersion is unstable and its preparation process is complex, and toxic zinc-containing accelerators should be used together for effective crosslinking. In recent years, synthesizing sulfur copolymers through inverse vulcanization of elemental sulfur and vinyl monomers has received widespread attention. Herein, self-emulsified sulfur copolymers (STD) were prepared by inverse vulcanization of elemental sulfur, polysorbide 80 and 1,3-diisopropylbenzene. The effect of monomer feed ratio on the structure and yield of STD was studied. According to laser particle size distribution analyzer and scanning electron microscope measurements, STD emulsion could be stably dispersed in water for a long time with an average size of about 80 nm. Further, STD was used as the crosslinking agent for carboxylated nitrile rubber latex, and the influences of STD content and composition on the properties of crosslinked rubber were systematically studied. The results showed that the fractions of sulfur and polysorbate 80 in STD determine the properties of crosslinked rubber by affecting crosslinking density and plasticizing effect, respectively. Compared with sulfur dispersion, STD emulsion is more stable with smaller micelle size and has higher reactivity, which avoids using toxic zinc-containing accelerators and imparts the crosslinked networks with better mechanical properties, thus exploring new avenue for the green crosslinking of rubber latex and the preparation of high-performance rubber materials.关键词：Inverse vulcanization;Rubber latex;Green crosslinking;Sulfur copolymer
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发布时间：2024-05-10 - 摘要：The frictional behaviors of implant soft materials in vivo are important to medical effect. In this study, hydroxyethyl acrylate sodium/acryloyldimethyl taurate copolymer (EMT-10) aqueous dispersions are adopted, acting as lubricants in hydrophobic polydimethylsiloxane elastomer (PDMS) Gemini interfaces or hydrophilic polyamide hydrogel (PAM) Gemini interfaces, respectively. The associations exist in EMT-10 aqueous dispersions via hydrogen bonding, electrostatic and hydrophobic interactions, similar to bio-lubricants. The EMT-10 aqueous dispersions, surface characteristics of Gemini interfaces and the axial force (Na) during frictional experiments in Stribeck curves are studied. Under low and high concentrations of EMT-10 lubricant, the PDMS Gemini interfaces exhibit opposing sensitivity to Na, different from the PAM Gemini interfaces, which always showing lower CoF at higher Na. This phenomenon results from the various degree of perfection for lubrication film between the Gemini interfaces. To further distinguish the lubrication film formation, and correlate frictional surface characteristic and rheological behaviors of lubricant, a new parameter, relative thickness (φ), is established. When φ<1, the lubrication film is discrete, and the boundary lubrication regime plays dominant role during the frictional test. When φ>1, the entire lubrication film forms and the whole system enters hydrodynamic lubrication regime. For PDMS Gemini interfaces, the lubrication film is composed of the confined and adsorbed EMT-10 polymer chains owing to the strong attraction between the hydrophobic surface and the C－C backbone. As a result, the lubrication film is greatly affected by the concentration of the lubricant thus φ increases. The PDMS frictional system gradually converts from the boundary into hydrodynamic lubrication regime. For PAM Gemini interfaces, the film is made of the hydrogel surface mesh and the confined EMT-10 chains, so φ is always larger than 1, exhibiting the characteristic of hydrodynamic lubrication regime. The study tends to probe the frictional behavior of the complex fluids in the soft Gemini interfaces and unveils the mechanism behind the phenomenon.关键词：Lubrication;Gemini interfaces;Polydimethylsiloxane elastomer;Hydrogel
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发布时间：2024-05-08 - 摘要：Biomimetic construction of extracellular microenvironment with dynamic viscoelastic behavior is an important strategy for the design of extracellular matrix (ECM) in tissue engineering. In this study, a poly(vinyl alcohol) (PVA)/cellulose nanofiber (CNF) composite hydrogel with anisotropic structure was constructed through the cooperative strategy of directional freezing (DF) and confined drying and re-swelling (CDR). The prepared composite hydrogel showed the oriented fiber arrangement structure parallel to the directional freezing direction. Rheological experiments showed that PVA/CNF composite hydrogel had anisotropic dynamic modulus (G'∥ = (76.77±1.61) kPa and G'⊥ = (42.93±1.34) kPa; G''∥ = (5.44±0.26) kPa and G''⊥ = (3.71±0.13) kPa). The energy storage modulus (G') and loss modulus (G'') improved with the increase of PVA content in the low frequency and low strain regions, and showed a tendency of increasing and then decreasing with the increase of CNF content. The results of stress relaxation experiments indicated that the composite hydrogel had viscoelastic properties. Therefore, the viscoelastic properties and rules of the composite hydrogel with anisotropic structures summarized in this study have potential applications in guiding the design of tissue-engineered biomimetic ECM and its effect on cell biological behavior.关键词：Anisotropy;Composite hydrogel;Extracellular matrix;Rheological behavior;Stress relaxation
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发布时间：2024-05-07 - 摘要：Elastomer materials with long-lasting and stable room-temperature phosphorescence have great potential in the fields of flexible electronics and photonics. However, developing such materials remains a daunting challenge. Systems of small molecule doped polymers are limited by the tensile properties of the polymer matrix. Currently commonly used polymethylmethacrylate (PMMA) and poly(vinyl alcohol) (PVA) have poor tensile properties. However, the increased flexibility cannot provide rigid external conditions for phosphorescence emission. This trade-off parameter adjustment has always hindered its development. Here, we report a highly stretchable and mechanically strong sustainable luminescent room-temperature phosphorescent covalent organic framework elastomer (SPU-D230-UPy COF) material. The material is composed of an alkyl chain soft segment and a limited covalent organic framework containing multiple hydrogen bonding hard segments. This structural design of separated soft and hard segments provides the structural basis for high mechanical properties, high toughness, and phosphorescent emission. The soft segment structure can ensure its high stretchability, and the hard segment structure can provide high mechanical strength while also providing a rigid environment for phosphorescence emission. These prepared elastomers exhibit high mechanical properties and high elasticity, and exhibit bright and sustained luminescence after removal of 365 nm excitation (luminescence time lasts for 3.0 s). Mechanical studies show that the obtained material exhibits a strength of ∼33.5 MPa and excellent toughness of ∼188.26 MJ/m3, with a Young's modulus of ∼76.6 MPa. The material can easily lift heavy objects without breaking. Impressively, these elastomers maintain strong optical properties even under repeated mechanical deformation, an unprecedented property. These outstanding properties make these long-lasting luminescent elastomers ideal for potential applications in wearables, flexible displays, and anti-counterfeiting devices. This separate structural design of soft and hard segments effectively breaks the trade-off between structural flexibility and phosphorescence emission. It can not only improve the mechanical properties, flexibility and stretchability of the material, but also effectively maintain the phosphorescence emission, which will provide a new path for the development of stretchable elastomer phosphorescent emissive materials.关键词：Elastomer;Covalent organic framework;ultralong room temperature phosphorescence;multiple hydrogen bonds
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发布时间：2024-04-29 -
Preparation and Research of Polyurethane Based Anti-icing Coating Based on Different Young's Modulus
摘要：Using 4,4'-diphenylmethane diisocyanate (MDI) and polytetrahydrofuran ether diol (PTMEG) as precursors, a one-component wet-cured polyurethane elastomer (PUE) coating with tunable Young's modulus (0.72-5.95 MPa) was synthesized by manipulating the R value. The effect of Young's modulus of coating on ice adhesion strength was studied by comparing polyether diols with different molecular weights. The results show that higher molecular weight series of polyether diols exhibit lower ice adhesion strength (average 57.71 kPa). As the Young's modulus of the coating increases, the corresponding ice adhesion strength initially rises and then declines. The analysis reveals that the surface of the coating with low Young's modulus (for example, PTMEG-1000 as the soft segment, 1.05-2.96 MPa) is easily deformed during water icing expansion, forming uneven structures and providing more adhesion points for the ice structure to adhere, which makes the ice adhesion strength closely related to the surface energy, resulting in the possibility of increasing the ice adhesion strength. However, the decrease interval of ice adhesion strength in coatings with higher Young's modulus (for example, PTMEG-1000 as the soft segment, 2.96-5.95 MPa) is not consistent with the positive correlation between Young's modulus and ice adhesion strength. This is due to the effect of low temperature resilience, the elastic mismatch between the ice and the coating induces micro-cracks and cavitation of the ice-coating interface, resulting in the possibility of reducing the ice adhesion strength. Therefore, understanding how coating's Young's modulus affects ice adhesion can be effectively utilized to reduce such adhesive properties.关键词：Polyurethane elastomer;Young's modulus;Ice adhesion strength;Mechanical property- 85
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发布时间：2024-04-28 - 摘要：The properties and applications of crystalline polymer materials largely depend on their crystallinity. Rapid preparation of highly crystalline or single crystal polymer materials is not only beneficial for studying their structure-property relationship, but can also expand their practical applications. However, efficiently and accurately assembling organic molecules into polymer single crystals through polymerization is a challenging task. To address this issue, our group has developed a supercritically-solvothermal method for achieving ultra-fast preparation of polymer single crystals. This method uses supercritical carbon dioxide as the reaction medium, which greatly improves the growth rate of polymer crystals due to its high diffusion rate and low viscosity. This feature article reviews the commonly used synthesis methods for covalent organic frameworks (COFs), as well as the challenges faced in single crystal preparation. Then, the basic properties and applications of supercritical fluids, the advantages of supercritically-solvothermal method, and the structural characterization of the prepared COF single crystals are systematically discussed. Finally, the challenges and development directions faced in the synthesis of polymer single crystals by supercritically-solvothermal method are prospected.关键词：Supercritically-solvothermal method;Polymer;Single crystal;Covalent organic frameworks;Fast synthesis
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发布时间：2024-04-24
- Postal code：100190
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