最新刊期
卷 54 ， 期 12 ， 2023
- 摘要：The rapid development of tough hydrogels has greatly expanded the application scope of gel materials. The strength and toughness of some synthetic hydrogels have surpassed those of soft biotissues, however, the elastic modulus of gels is usually less than 1 MPa, much lower than that of connective tissues such as tendons. One major reason is the water molecules have strong hydration and plasticizing effects on hydrophilic polymer network, resulting in the gels in the elastic or viscoelastic state. In recent years, we have developed high-performance (high strength, high stiffness, high toughness) hydrogels through molecular design to form dense and robust associative interactions within the matrix that effectively reduce the dynamics of the network to afford the gel in a glassy state at room temperature. The glassy state is one new state of gel materials, which opens a new avenue to develop high-performance hydrogels and broadens the tuning range of mechanical and viscoelastic behaviors as well as the application potentials. This account summarizes and reviews the synthesis and structure-property relationship of glassy hydrogels, including the general characters, molecular mechanism, design principles, and unique functions. Finally, we introduce some applications of glassy hydrogels in the fields of biomedicine, engineering, etc., and give prospects to the challenges and future directions in this area.关键词：Hydrogels;Glassy state;Associative interactions;Mechanical properties;Rheological behavior
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发布时间：2024-03-28
Feature Article
- 摘要：In view of the application demand for rigid structural foam in the extremely low-temperature environment in the aerospace field, polymethacrylimide (PMI) structural closed foams were prepared by thermal foaming of the copolymer sheet prepared by bulky radical copolymerization of methylacrylonitrile (MAN) and methacrylic acid (MAA). The reaction mechanism of PMI foam preparation process was analyzed. The thermal and mechanical properties of PMI foam as well as its structural and performance stability after being treated with liquid hydrogen (LH2: -253 ℃) and liquid oxygen (LO2: -183 ℃) were systematically studied. Experimental results indicated that the imide cyclization reaction was the main reaction in the foaming process, which occured above 160 ℃. The PMI foams obtained showed excellent mechanical, thermal and heat insulation properties at ambient temperature. The glass transition temperature of PMI foam was 202 ℃, and the initial thermal decomposition temperature was higher than 300 ℃. The compressive strength was 3.99 MPa with density of 111 kg/m3. After treated in liquid hydrogen and liquid oxygen at extremely low temperatures for 1 h, no obvious change was detected on the chemical structures and combined properties of the PMI foams. Otherwise, the PMI foam showed excellent mechanical properties at -150 ℃, with compressive strength and modulus which were higher than that measured at room temperature (25 ℃), and tensile strength and elongation at break which were 70% and 48% of that at 25 ℃, respectively. The excellent high and low temperature resistance of PMI foam makes it expected to be used in the preparation of the structural parts of cryogenic propellant tank.关键词：Polymethacrylimide foam;Liquid hydrogen;Liquid oxygen;Propellant tank
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发布时间：2024-03-28 - 摘要：Silicone, alkyne and naphthalene groups are introduced into polyimides to obtain novel polyimides with good thermal and processing properties. Asymmetric diamine (3-aminophenyl)-(4'-aminophenyl)-acetylene (AMPA) and 3-(naphthalene-1-acetylene) aniline (NAA) naphthalene rings were synthesized by Sonogashira reaction. Then using AMPA, NAA, bis(3,4-dicarboxyphenyl) dimethylsilane di-anhydride, 4,4'-diphthalic anhydride (ODPA) and m-aminobenzene (APA) as raw materials, a series of polyimide resins PI-Si-Ⅰ (APA as the terminating agent) and PI-Si-Ⅱ (NAA as the terminating agent) containing silicon and endoalkynyl groups in molecular chains were prepared with control group PI-O-Ⅰ and PI-O-Ⅱ (ODPA as the monomer of dianhydride). The PI-Si resins had high solubility in common solvents such as tetrahydrofuran (THF), low melt viscosity and wide processing window of Pi-Si-Ⅱ resin. The processing window of resin was 100 ℃. The curing thermal behaviors of the resins were tracked by differential scanning calorimetry (DSC). The results showed that each resin had two curing peaks, the first peak appeared in the range of 285‒328 ℃ with the peak temperature at 311 ℃, and the second peak appeared in the range of 350‒422 ℃ with its second peak temperature at 390 ℃. The thermogravimetric test showed that the Td5 of cured resin was 547 ℃, and the R800℃ exceeded 79%, suggesting their excellent heat resistance. The thermal cracking analysis of the cured resins showed that the silico-oxy-silicon structure, benzene ring and naphthalene ring rigid structures were formed when silicomethyl and acetylene groups were introduced into the main polyimide chain at high temperature, which improved the heat resistance of the resin.关键词：Polyimide;Processability;Thermal properties;Naphthalenic unit;Silicon
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发布时间：2024-03-28 - 摘要：In recent years, there has been a great emphasis on improving the value of polyethylene (PE) products by developing high-performance PE products. Post-functionalization modification of PE is an effective method to achieve this goal. The use of additives for functionalized modification of PE is a straightforward and economical approach. However, most additives are organic small molecule compounds that tend to migrate, evaporate, or get lost from the polymer matrix through solvent extraction during the use of polymer products. This results in a decrease in product performance and poses a threat to human health, especially in the field of food packaging. Modifying small molecular additives by macromolecules has emerged as current research frontiers to address the aforementioned issues. This study aims to create macromolecular functional additives using functionalized PE with coumarin as the side groups. A PE derivative with coumarin as the functional side group is synthesized using the Mitsunobu derivatization reaction of commercial poly(ethylene-co-vinyl acetate) (EVA). The polymer structures are confirmed through infrared and nuclear magnetic resonance characterization. When used as an additive for PE, it not only provides antibacterial and antioxidant properties to the substrate, but also resists ultraviolet ageing. Additionally, it outperforms commercial UV absorbers (UV-329) by effectively avoiding the additive migration while maintaining superior UV ageing resistance.关键词：Functional modification of polyolefins;Coumarin and its derivatives;Polymer additives
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发布时间：2024-03-28 - 摘要：To prepare a water-based epoxy resin with stable superhydrophobicity, we need to prepare the silica with different particle sizes (micron, submicron, nanometer) based on the alkaline hydrolysis reaction of 3-aminopropyltriethoxysilane (KH550), γ-glycidyloxypropyltrimethoxysilane (KH560) and methyltrimethoxysilane (MTMS). Strawberry-like SiO2 (CM-SiO2) multiple particles with multi-scale effect were then synthesized through the grafting reaction of layer-by-layer assembly. At the same time, as a comparison, the single-coated hydrophobic SiO2 with a smooth surface was prepared. The morphology and structure of the two types of particles were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS), while the similarities and differences can also be compared. The self-made modified particles were blended with water-based epoxy resin (WEP) to construct a rough micro-nano structure on the surface of the coating to prepare a water-based epoxy resin coating with superhydrophobic properties. Differential scanning calorimetry (DSC) and thermo gravimetric analyzer (TGA) were applied to characterize the blending performance and heat resistance of coatings. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to quantitatively analyze the characteristics of the coating and its surface morphology. The superhydrophobic properties of the waterborne coatings and the variation of surface energy were characterized by the contact angle test (WCA). The results show that compared with the smooth particles coated with a single layer, the modified SiO2 particles with multi-layer structure migrated to the surface of WEP and constructed the micro-nano structure, which is more conducive to the formation of superhydrophobicity. In addition, the rough coating has an excellent self-cleaning effect and can maintain the stability and durability of the structure in harsh environments, reflecting excellent abrasion resistance and chemical corrosion resistance.关键词：Particles design;Water-based epoxy resin;Superhydrophobicity;Micro-nano structure;Self-assembly
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发布时间：2024-03-28 - 摘要：Four kinds of castable poly(urethane-urea) elastomers (PUU-s) were prepared by introducing different contents of hydroxy-terminated polydimethylsiloxane (PDMS) to the PUU, which was synthesized with polytetramethylene ether glycol (PTMEG), 2,4-diisocyanato-1-methylbenzene (TDI) and 4,4'-methylene-bis(2-chloroaniline) (MOCA). The effects of PDMS content on the mechanical properties, heat resistance, fatigue resistance, recoverability, dielectric resistance, and tribological properties of PUU-s were systematically studied. The results show the diamine used as curing agent reacted with ―NCO and yielded the urea group, which offer high density hydrogen bonding sites that allows the PUU elastomers to perform an excellent mechanical properties. The tensile strength, elongation at break and toughness of modified PUU-4 wt% elastomers are (36.6±1.3) MPa, (527.6±10.9)% and (88±4.7) MJ/m3, respectively. While PDMS was introduced to the PUU through chemical bonding, the PDMS content affects the physico-chemical properties of the PUU. The transition temperature of PUU-s elastomer decreases from -24.3 ℃ to -26.4 ℃ with the increase of PDMS content. The lower surface energy of PDMS endows PUU-s elastomer with excellent heat resistance (THRI = 165.95 ℃) and hydrophobic properties (surface energy = 44.8 mN/m). In addition, due to the enrichment of PDMS on the surface of PUU-s elastomer, the wear loss and friction coefficients decreased from 0.074 cm3/1.61km and 0.2 to 0.022 cm3/1.61km and 0.05, respectively. The excellent anti-wear resistance is comparable to that of commercial high-performance thermoplastic polyurethane. Moreover, the poly(urethane-urea) elastomer prepared in this study possesses excellent solvent resistance, the tensile strength remains (45.48±7.3) MPa even after long-term immersion in 80 ℃ water, which indicates the long service life of our PUU elastomer as sealing material. On one hand, the flexibility of PDMS could reduce the intramolecular friction, on the other hand, the dynamic dissociation and recombination of high-density hydrogen bonds consumes partially solve the friction heat accumulation caused wear and sealing failure. Therefore, the PUU synthesized here can be used as a sealing material under harsh conditions, such as the sealing material for the main drive of the tunneling boring machine.关键词：Poly(urethane-urea);tribological properties;Silicone resin;sealing materials
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发布时间：2024-03-28 - 摘要：The preparation of block copolymer microparticles that change morphology in response to multiple external stimuli is of great significance for the development of new smart materials. This work proposes a new strategy to control the morphology transition of block copolymer microparticles by taking advantage of temperature/pH dual-responsive polymeric co-surfactant, poly(acrylic acid)-b-poly(N-isopropylacrylamide) (PAA-b-PNIPAM). The transformation of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) microparticles among pupa-like particles, strawberry-like particles, and onion-like particles could be realized by tuning the volatilization temperature and the pH value of the aqueous phase. This morphological transformation depended on the hydrophilic and hydrophobic transformation of PAA-b-PNIPAM regulated by temperature/pH, which changed the distribution of co-surfactant at the interface, resulting in the change of the interface selectivity of oil/water interface and the morphology of the microparticles. Moreover, the effects of temperature/pH on the morphology transition mechanism of PS-b-P4VP microparticles were systematically studied by means of changing the mass fraction of PAA-b-PNIPAM and the block ratio of PAA to PNIPAM. This work provides a new way for shaping the microparticle morphology of inert block copolymers via the introduction of temperature/pH dual-responsive co-surfactant. Such dual-responsive microparticles are expected to be used in drug release, smart delivery, and other areas.关键词：Block copolymers;Confined assembly;Polymeric microparticles;Stimuli-responsiveness;Morphological transformation
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发布时间：2024-03-28 - 摘要：A room-temperature approach based on the solution surface for the fabrication of polyaniline (PANI) film and gas sensitive devices was introduced in this study. The protonated PANI film was directly produced on the surface of the aqueous solution through oxidation polymerization way, only using the aniline monomer, hydrochloric acid, and ammonium persulfate as raw materials. The gas sensitive device was subsequently built based on the transferable properties of the film. A mechanism for PANI film production was therefore proposed, according to which protonated aniline monomers preferentially aggregate and polymerize on the solution surface. It was discovered that the pH of HCl solution was crucial for the creation of the PANI dense film. The film gas-sensitive device was successful in detecting NH3 at room temperature, and the response varied regularly with the temperature and duration of film polymerization. The resulting film has a lower detection limit of 0.7 mg/m3, a good linear response to NH3 in the range of 0.7‒140.0 mg/m3, good repeatability, selectivity, rapid response, and competitive response value under optimal fabrication conditions (pH=0.6, room temperature 18 ℃, and plolymerization of 60 min). Obviously, the fabrication process is environmentally friendly, the film can be produced across a vast surface area, and it exhibits outstanding gas sensitivity performance, all of which are anticipated to provide a new route for the fabrication of PANI-based films as well as for the research and application of room-temperature gas sensors.关键词：PANI film;Polymerization on solution surface;Room-temperature fabrication;Room-temperature gas-sensing performance;Ammonia Gas
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发布时间：2024-03-28 - 摘要：Blending of isotactic polybutene-1 (iPB-1) and isotactic polypropylene (iPP) is a facile way to obtain polymer materials with excellent performance. However, the interfacial structure that determines the properties of the iPB-1/iPP blends has rarely been studied. In this study, a bilayer film of iPB-1 and iPP that was fabricated by hot-pressing was used to analyze the influence of thermal annealing temperature and crystallization temperature on the interfacial structure and bond properties of iPB-1/iPP blend via tearing experiment, scanning electron microscope (SEM), and transmission electron microscope (TEM) observation. It is found that the interfacial bonding strength of iPB-1/iPP blends significantly decreased with the thermal annealing, and the higher annealing temperature resulted in the lower interfacial bonding strength and a lower rough tear surface. Also, the iPB-1/iPP blend that underwent two-step crystallization involving the crystallization of iPP at 130 ℃ and then the crystallization of iPB-1 at 60 ℃ after thermal annealing exhibited a higher interfacial bonding strength and a rougher tear surface than those of the samples which underwent one-step crystallization involving the crystallization of iPP and iPB-1 at 60 ℃. After two-step crystallization, a thicker interfacial layer was observed by TEM, and the diffusion of iPB-1 molecular chains towards the iPP phase region was also observed.关键词：Isotactic polybutene-1;Isotactic polypropylene;Blending modification;Interfacial structure and property
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发布时间：2024-03-28 - 摘要：In order to fabricate cation exchange membrane with good permselectivity of proton/divalent metal ions, the influence of functional group (quaternary ammonium group and carboxyl group) content on the membrane performance was investigated. The ionic polysulfone (PSF) with pendent quaternary ammonium group and carboxyl group was synthesized by "click chemistry" reaction and blended into sulfonated polyether ether ketone (SPEEK). The content of quaternary ammonium group in the blend membrane was adjusted by the amount of ionized PSF, the functionalization degree of PSF and the ratio of quaternary ammonium group to carboxyl group, respectively. With the increase of ionized PSF content, the water uptake rate, swelling degree and proton flux of blend membrane gradually decreased, while the membrane surface resistance increased. The permselectivity of blend membrane for hydrogen and ferrous ions increased first and then decreased with the increase of ionized PSF content. When the ionized PSF content was 40%, the highest permselectivity of blend membrane (312.86) was obtained, which was 38 times that of SPEEK. Its proton flux (3.51 mmol·m-2·s-1) decreased to 38% that of SPEEK membrane (9.23 mmol·m-2·s-1). The permselectivity of blend membrane increased first and then decreased with the increasing functionalization degree of ionized PSF. The permselectivity of PSF-X10Y10 membrane was 12 times and 3.5 times that of PSF-X6Y6 and PSF-X15Y15 membranes, respectively. The permselectivity of PSF-X10Y10 membrane was 4 times and twice that of PSF-X7Y13 and PSF-X13Y7 membranes, respectively. The formation of ion pairs between quaternary ammonium group and sulfonic acid group was beneficial to inhibit membrane swelling, and the permselectivity of membrane was improved via Donnan repulsion and size-sieving effect. However, when the content of quaternary ammonium group exceeds a certain value, the formation of ion clusters leads to the uneven distribution of functional groups in the membrane, and the permselectivity of the membrane decreases. The reduction extent of proton flux could be decreased by increased carboxyl group content via the formation of hydrogen bond.关键词：Cation exchange membrane;Permselectivity;Click chemistry;Ion cluster
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发布时间：2024-03-28 - 摘要：The application of polymer based solid-state ion thermoelectric batteries to convert low-quality heat energy into electrical energy is an effective way to improve energy comprehensive utilization. Using chitosan as the matrix, a high ion conductivity and high thermal power based ion thermoelectric material (CGH-G) was prepared by grafting dicyandiamide and guanidine ions, which enhances the flexibility and dimensional stability of the material. Due to the introduction of two positively charged amino ions, the thermal diffusion effect of ion pairs is significantly enhanced, while the thermal work rate of the material is increased from 2.16 mV/K to 4.84 mV/K, and the impedance of the thermoelectric material is significantly reduced. The prepared chitosan based ion thermoelectric material is assembled into a quasi-solid-state ion thermoelectric cell. Under the environmental conditions of a temperature difference of 25 K and an external 5 Ω load, the power density can reach 1.33 W/m2 while achieving a high energy density output of 25.43 J/m2. In addition, multiple flexible ion thermoelectric batteries connected in series exhibit high output stability, demonstrating the broad application prospects of chitosan-based ion thermoelectric materials in waste energy utilization.关键词：Chitosan;Quasi solid state ion thermoelectric materials;Ion pyrogen battery;Power density;Energy density
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发布时间：2024-03-28 - 摘要：When polymer melts crystallize under high pressure, they often exhibit completely different crystallization behaviors from atmospheric crystallization. This difference is not only manifested in crystallization kinetics, but also in the crystal structure of the product. The crystallization behavior of iPB-1/iPP blends under different pressure was studied by means of wide-angle X-ray diffraction (WAXD), differential scanning calorimeter (DSC) and scanning electron microscopy (SEM) in this study. The results showed that under higher pressure the phase separation of iPB-1 and iPP was effectively inhibited, and the size of the phase domain of iPB-1 was reduced, thus the nucleation and growth of form II in iPB-1 was inhibited, which was benefit for the formation of form I'. At the same time, γ-iPP crystal could also induce the nucleation of form I'. The synergy of high pressure and γ-iPP could also further improve the structural stability of form I' of iPB-1, and make form I' phase stable under the high pressure range from 200 MPa to 500 MPa. In iPB-1/iPP blends, the smaller phase domain of iPB-1, the formation of form I' and γ-iPP could improve the breaking strength and elongation at break of products, therefore improve their mechanical properties.关键词：Polybutene-1/polypropylene blends;High-pressure crystallization;Structural stability;Mechanical property
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发布时间：2024-03-28 - 摘要：The polymer tethered with nanoparticles at two ends is a preferred molecular model for studying the effect of the chain end on the relaxation behavior of polymers. We constructed a polymer model with two nanoparticles tethered at each end and used coarse-grained molecular dynamics to study the characteristic temperature and relaxation behavior of these polymers. The effects of nanoparticle radius and polymer length on the glass transition temperature, crystallization temperature, and dielectric properties were examined. We found that two apparent transitions occur during the annealing. The high-temperature transition corresponds to the crystallization due to the existence of nanoparticles at ends, and the low-temperature transition is the glass transition related to polymer chains. The presence of nanoparticles at both ends of the polymer can delay the relaxation of the polymer chain and promote crystallization, resulting in an increase in the glass transition temperature and crystallization temperature of the polymer as the nanoparticle becomes large or the polymer chain shortens. The chain relaxation was further studied by calculating the relaxation correlation functions and dielectric relaxation spectra. The work revealed that the dielectric loss peak shifts towards low frequencies as the nanoparticle radius increases or the polymer chain length decreases. We finally compared the simulation results with existing experimental findings, and an agreement was achieved. The work can deepen the understanding of the structure and properties of the polymer with two nanoparticles tethered at each end.关键词：Relaxation;Glass transition;Molecular dynamics;Polymer-grafted nanoparticle
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发布时间：2024-03-28
Research Article
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