最新刊期
卷 51 ， 期 12 ， 2020
- 摘要：Since the COVID-19 epidemic, the global demand for medical supplies, e.g., disposable medical masks (DMMs), have been largely increasing. Blocking bacteria and virusesvia wearing masks, according to the pre-judgment of epidemic infectious disease experts, will be a normal phenomenon within a long future period. Therefore, how to process the large number of waste DMMs properly is becoming an important issue for various countries and regions all over the world. From the view of chemical upcycling, this paper reviews the current status of recycling, and prospects the upcycling of polypropylene (PP), which is the main component of DMMs. The upcycling methodologies here mainly include mechanical blending, chemical modification, controllable degradation and physical process modification. Both the advantages and disadvantages of these methodologies have been discussed based on the analysis of technological feasibility and economic benefit. On the basis of the formation of public awareness of recycling and treatment of waste DMMs, by exploring the mechanism of decomposition, reconstruction and re-functionalization of PP, developing new selective green catalysts, degradants, in situ collaborative detection technologies, utilizing the residual value of the existing waste DMMs, etc. will greatly promote the upcycling of waste DMMs. It is believed that converting waste PP selectively into a single type of chemicals, fuels and high value-added material by chemical ways is the fundamental method to realize the transformation of waste DMMs from “waste” to “treasure” and sustainable development.关键词：Disposable medical masks;Polypropylene;Recycling;Chemical upcycling
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发布时间：2021-01-26 - 摘要：Zwitterionic hydrogels have received considerable attention owing to their characteristic structures and properties. Bearing high density of oppositely charged groups within polymer networks at the micro-scale, the zwitterionic hydrogels exhibit a macroscopic electro-neutrality. As a result, the soft matter exhibits various specific features, such as high hydrophilicity owing to their dense charged groups, “anti-polyelectrolyte behavior” due to salt clearable associations between oppositely charged groups, and UCST-type thermo-responsiveness as a result of temperature-sensitive polymer inner and inter-chain associations. In this review, the unique properties of the materials are described at first, and their potential applications including biomedicine, gel polymer electrolyte, sensor, and actuator are subsequently illustrated in detail. Thereafter, the possible constraints that hinder their current practical application are well discussed. The difficulty in monomer synthesis, the relatively poor chemical stability against long term hydrolysis and oxidization in aqueous media, and unsatisfactory mechanical performance are three main plausible reasons. Developing zwitterionic hydrogels with ameliorated chemical structures effectively enhances their chemical stability, while the exploration of polyzwitterionic composite hydrogels with nanoparticles is a possible way to figure out the existing drawback of poor mechanical performance. In the end, current status as well as future prospect of the zwitterionic hydrogels are finely presented.关键词：Zwitterionic;Hydrogel;Biomedicine;Gel polymer electrolyte;Sensor;Actuator
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发布时间：2021-01-26 - 摘要：As a kind of special engineering plastics, poly(aryl ether ketone) has excellent comprehensive properties, making poly(aryl ather ketone) have broad application prospects in many fields. Research progress of poly(aryl ether ketone) fibers and structure optimization of poly(aryl ether ketone) on spinnability are introduced from amorphous poly(aryl ether ketone) and crystalline poly(aryl ether ketone). There are some differences in solubility, processing methods, aggregation structure and application fields between amorphous poly(aryl ether ketone) and crystalline poly(aryl ether ketone) fibers. At present, more studies have been done on crystalline poly(aryl ether ketone) fibers than on amorphous poly(aryl ether ketone) fibers. In terms of physical modification, poly(aryl ether ketone) blends with inorganic lubricants, thermotropic liquid crystalline polyester and thermotropic liquid crystalline poly(aryl ether ketone). Processability of the blend and mechanical properties of the fibers are improved significantly. In terms of chemical modification, poly(aryl ether ketone) is modified by sulfonation, chloromethylation, ring opening polymerization, multicomponent copolymerization, introduction of mesogenic units or different side groups, introduction of twisted non-coplanar structure and introduction of thermotropic liquid crystalline polyester. Processing methods of poly(aryl ether ketone) are expanded and the solubility of poly(aryl ether ketone) is improved. Ionic conductivity of poly(aryl ether ketone) nanofiber membrane is also improved. Blending with inorganic lubricant, blending with thermotropic liquid crystalline polyester, blending with thermotropic liquid crystalline poly(aryl ether ketone), sulfonation, introduction of different side groups and introduction of twisted non coplanar structure play an important role in crystalline poly(aryl ether ketone). While, chloromethylation, ring opening polymerization, multicomponent copolymerization and introduction of thermotropic liquid crystalline polyester play an important role in amorphous poly(aryl ether ketone). By chemical modification, the application of poly(aryl ether ketone) nanofiber membrane in ion-exchange membrane of fuel cell and many other promising fields are expanded. In corresponding fields, the structure and properties of amorphous and crystalline poly(aryl ether ketone) still have great potential for improvement. Hope this paper could provide reference for the other researchers.关键词：Poly(aryl ether ketone);Fibers;Structural optimization of polymer;Liquid crystal phase;Post functionalization
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发布时间：2021-01-26 - 摘要：Chitosan (CS) hydrogel based adhesives have good biocompatibility, but poor adhesive property. In this paper, catechol modified chitosan (CS-pC) was synthesized by modifying CS with 3,4- dihydroxybenzoic acid. The mass ratio of catechol group of CS-pC is 14.4%. When the CS-pC acetic acid aqueous solution and the aqueous solution of β-glycerol phosphate disodium salt (β-GP) is mixed, an injectable CS-pC/β-GP sol is formed, which can be transformed into CS-pC/β-GP hydrogel under heating. The sol-gel transition time decreases exponentially with the increase of the temperature, and is around seven minutes at 37 °C. The CS-pC/β-GP hydrogel has good biocompatibility, showing no cytotoxicity to Hela cells, MCF-7 cell, as well as 293T cells. It has excellent antibacterial properties on killing Escherichia coli and Staphylococcus aureus. It is noted that the CS-pC/β-GP hydrogel has brilliant adhesion property. The CS-pC/β-GP hydrogel can adhere to the porcine skin tightly. The critical peel strength is up to 4.9 kPa, eight times higher than that of the hydrogel prepared from unmodified CS (0.6 kPa). Furthermore, the water-soluble drug doxycycline hydrochloride (DH) and near-infrared (NIR) photothermal agent gold nanorods (AuNR) can be loaded into the CS-pC/β-GP sol to form an injectable CS-pC/β-GP/DH/AuNR sol, which can also be transformed into CS-pC/β-GP/DH/AuNR hydrogel rapidly at 37 °C. The strong NIR photothermal conversion effect of the loaded AuNR offers the hydrogel a remarkable NIR light controlled release function. The release rate of the loaded DH will increase six times under the irradiation of 808 nm NIR laser, which indicates that the CS-pC/β-GP/DH/AuNR hydrogel adhesive can also achieve a controlled wound healing. This work provides a new way for the development of safe, high-performance, and multifunctional injectable catechol modified chitosan based biological adhesives.关键词：Chitosan hydrogel;Injectable sol;Biological adhesives;Near-infared-light-controlled release
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发布时间：2021-01-26 -
Enhancement of Nonleaching Antimicrobial Poly(vinyl alcohol)/Poly(hexamethylene guanidine) Hydrogels
摘要：A novel nonleaching antimicrobial poly(vinyl alcohol)/poly(hexamethylene guanidine) hydrochloride (PVA/PHMG) hydrogel was prepared with freezing-thawing method. The hydrogen bond interaction between PVA and PHMG confirmed by ATR-FTIR spectra, endowed PVA/PHMG hydrogels with the nonleaching characteristic. These antimicrobial hydrogels behaved above 99.9% of antimicrobial rates against both E. coli and S. aureus, even after washing or soaking in water for 7 days. The PVA-0.100wt%PHMG hydrogel had 120% higher tensile strength than pure PVA hydrogel due to the reinforement of hydrogen bonding between PVA and PHMG. Furthermore, GO (graphene oxide) and SiO2 were respectively added to the PVA-0.100wt% PHMG system to reinforce the mechanical properties. PVA/PHMG/GO hydrogel and PVA/PHMG/SiO2 hydrogel were also prepared via freezing-thawing method. These two composite hydrogels still showed nonleaching antimicrobial properties and the antimicrobial rates were above 99.99% even after washing or soaking in water for 7 days. Compared with PVA/PHMG hydrogel, the ―OH peak of the PVA/PHMG/SiO2 hydrogels in the infrared difference spectra shifted to the lower wavenumbers by 38 cm−1, while the ―OH peak of the PVA/PHMG/GO hydrogels shifted by 23 cm−1. Therefore, the hydrogen bonding effect of SiO2 with PVA/PHMG might be stronger than that of GO. The hydrogen bond interactions among reinforcing agents, PVA and PHMG significantly enhanced the tensile strength of the hydrogel. The tensile strengths of PVA/PHMG/GO and PVA/PHMG/SiO2 hydrogels were 1.6 times and 3.3 times of that of PVA/PHMG hydrogels, respectively. This study provides a simple approach to develop reinforced and nonleaching antimicrobial PVA hydrogels.关键词：PVA hydrogel;Hydrogen-bond;Antimicrobial performance;Enhancement- 152
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发布时间：2021-01-26 - 摘要：In order to solve the problem of oily wastewater, the poly(m-phenyleneisophthalamide) (PMIA) braided tube reinforced (PBR) poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether)(PFA) hollow fiber membrane was prepared via dipping-sintering method with the PFA and poly(vinyl alcohol)(PVA) as membrane-forming polymer and bonding agent, respectively. The membrane surface structure was adjusted by changing the sintering temperature and graphene (GE) content, and the influence of membrane structure and oil-water separation performance were investigated by scanning electron microscopy (SEM), thermogravimetric (TG), Fourier transform infrared (FTIR), pore size analysis and oil-water separation experiment. The morphology observation shows that the surface PFA melts and permeates into the PMIA braided tube after sintering, and separation layer is closely combined with the support layer. The experiment results also indicate that with sintering temperature increasing, the oil flux decreases. On the other hand, with GE content increasing, the water contact angle, roughness, and porosity of PBR-PFA/GE hollow fiber membrane decrease, however, the oil flux increases initially and then decreases, the oil-water separation efficiency increases gradually. Furthermore, the introduction of GE not only has a similar effect on the increase of sintering temperature, but also results in two different ways of pore formation on the membrane surface. The PBR-PFA/GE hollow fiber membrane exhibits excellent hydrophobicity and lipophilicity with more than 97% separation efficiency for different oil products at −0.02 MPa. In addition, the membrane shows higher separation ability to the water-in-oil emulsion, and maintains a fine flux recovery rate after recycling, making it possible to apply in the field of wastewater treatment.关键词：Poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether);Graphene;Reinforced;Hollow fiber membrane;Oil-water separation
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发布时间：2021-01-26 - 摘要：In order to prepare organic piezoelectric materials with good piezoelectric properties and enhance the intrinsic piezoelectric properties of the poly(vinylidene fluoride) (PVDF) crystal phase, a solution coating film-forming process was adopted to prepare PVDF films. The films with different stretch ratios (R = 3,5,7) were made by uniaxial stretch process. The morphology and structure of the films were investigated by scanning electron microscopy (SEM), transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC). Gold electrode is sprayed on the surface of the film and then the film is subjected to high-voltage electric field polarization treatment. Connect the films to the sampling multimeter to further study the piezoelectric properties of the films. It shows that uniaxial stretch can increase the crystallinity of PVDF and promote the transformation of α phase into β phase. During the stretch process, the molecular segments of PVDF are highly oriented to form the β phase of the all-trans conformational structure. The larger the stretch ratio, the higher the crystallinity of PVDF and the higher the relative content of the polar β phase. When the stretch ratio is 7, the relative content of β phase increases to 85.12%, which is 1.5 times higher than that of the unstretched film. Since the intrinsic piezoelectric properties of PVDF are controlled by its crystalline β phase content, the larger the stretch ratio, the better the ferroelectric and piezoelectric properties of the film. The film exhibits the best electrical properties when it is stretched 7 times: When the applied electric field is 200 MV/m, the residual polarization intensity reaches 2.69 μC/cm2. When the strain is 5%, the average output current density is 58.92 nA/cm2, and the average output voltage is 89.70 mV. In this study, the single-axis stretched PVDF film has a high voltage sensing sensitivity, and a PVDF film in a small area size (22 mm × 4 mm) can provide an output voltage as high as 89.70 mV. Therefore, the material can be used to produce ultra-thin, lightweight portable electronic devices in ideal shape, and is expected to be used as a flexible touchable sensor to obtain biomechanical energy from the human body for health monitoring.关键词：PVDF film;Uniaxial stretch;Crystal transition;Piezoelectric response
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发布时间：2021-01-26 - 摘要：The soft and hard acid-base theory (HSAB) is a new acid-base theory created by Sir. Pearson based on the theory of Lewis acid-base electron. It can be used to explain various chemical reactions, especially in coordination chemistry. In this study, the synthesized Cat.1 − Cat.6 [N,P]Ti catalysts containing ligands with electron withdrawing groups were prepared for ethylene polymerization without the addition of cocatalyst. The other optimal conditions for ethylene polymerization were determined through optimizing the polymerization behavior. Cat.5 with ligand L5 containing tetrafluorobenzene ring showed a catalytic activity of to 2.83 × 105 gP∙(molM) −1∙h−1 for this polymerization. The obtained polyethylene featured high weight average molecular weight of 8.6 × 105 g/mol. The molecular weight distribution of polyethylene obtained by these six catalysts were in 2.2 − 2.5, and the melting point was about 135 °C The reaction mechanism of ethylene polymerization was explored by HSAB. The results showed that when the substituent on the catalyst aniline was an electron withdrawing group, both the polymerization activity and the molecular weight of the obtained polymer were higher. Density Functional Theory (DFT) results indicated that ethylene was more inclined to react with one of the M―C bonds of the catalyst. The energy barrier for the ethylene insertion reaction by Cat.5 was the lowest, compared to other catalysts except Cat.1, which made ethylene insertion reaction easier. These ligands containing electron withdrawing groups on aniline ring made the catalytic active species more stable. Much higher molecular weight of polyethylene was produced by utilizing these catalysts with the ligands containing electron withdrawing groups on aniline ring. These experimental results were consistent with those of HSAB and DFT.关键词：[N,P]Ti catalysts;Without cocatalyst;Ethylene polymerization;Soft and hard acid-base theory;Density functional theory
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发布时间：2021-01-26 - 摘要：The styrene/butadiene copolymer is widely used as elastomer in various applications of packing material, such as shoes, asphalt modifiers, etc. The control of structure is the key to control the properties of material. Living anionic polymerization is still state of the art for the precise preparation of SBC. However, the sequence distribution of the copolymerization of styrene and butadiene cannot be as precise as that of styrene and DPE derivatives, because the product of reactivity ratios of styrene and butadiene is not approximately equal to 0. The composition distribution control was proposed to describe the behaviour of monomers in the statistical anionic copolymerisation. Herein, the primary amine DPE derivative was copolymerized with styrene and butadiene. In the terpolymerization, two primary amine functionalized SBC with similar molecular weight but different composition distributions were synthesized by varying feeding orders (i.e. ran-NFSBC and grad-NFSBC). The kinetics of copolymerizations were calculated. In ran-NFSBC, the reactivity ratio of St to DPE derivative was 2.58. The conversion of primary amine DPE derivative was 71.7%. The composition distribution was random distribution. Ingrad-NFSBC, the primary amine DPE derivative was totally consumed. The composition distribution was determined to be gradient distribution using the timing sample method. Finally, the relationship between composition distribution and thermal behavior of SBC was preliminarily studied by DSC.关键词：Living anonic polymerization;Amine functionalzied;Styrene/Butadiene copolymer;Composition distribution
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发布时间：2021-01-26 - 摘要：The melt strength of polyolefin materials could be enhanced by graft modification, since the introduction of long side chains could result in entanglement among the chains and thus improve the foaming properties. Herein, polybutylene (PB) with the improved foaming property was produced by melt grafting of octadecyl methacrylate (SMA) as long side chains. It was found that the chain entanglement was increased and the foaming behavior was improved. The structure was characterized by infrared (IR) spectroscopy, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Compared with un-modified PB, the tensile strength of the modified PB decreased, whereas its impact strength firstly increased and then decreased when increasing the amount of SMA. DSC curves showed that the crystallinity of PB decreased when increasing the grafting dosage. The SEM images showed that all the parameters including the average cell size, cell size distribution, and cell density of foam beads were improved after introducing the longside chains. When the weight ratio of SMA/PB was 3/100, the average cell diameter of PB was 12.3 μm, the cell density was 38 × 107 cells/cm3, and the expansion ratio was 12. The cell density and expansion ratio of PB with longside chains were 9.2 times and 1.6 times respectively as many as those of un-grafted PB produced with the same foaming method. Additionally, the grafted PB exhibited a wider foaming temperature range.关键词：Polybutylene;Grafting chain;Foaming
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发布时间：2021-01-26
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