最新刊期
卷 52 ， 期 3 ， 2021
- 摘要：Surface modification of biomaterials via graft polymerization has become one of the most important methods to enhance their virtual bio-functionalities. Compared with other living graft polymerization methods, photo-initiated living graft polymerization exhibits superior merits and has been more and more widely used in surface modification of biomaterials. The photoinitiators used for photo-initiated living graft polymerization are mainly categorized into three types: photoiniferter-mediated polymerization (PIMP), benzophenone and its derivatives, and thioxanthones. In this review, the development, graft mechanism and characteristics of the three photo-initiated living graft polymerization systems are briefly introduced. Meanwhile, the applications of photo-initiated graft polymerization in three different biomedical fields are mainly reviewed. i) Antibacterial surface: layered functional polymer brushes constructed by photo-initiated living graft polymerization have been developed to achieve antibacterial function on demand; ii) Immunoassay: layered functional polymer brushes can solve the problem of low detection sensitivity and protein interference; iii) Bioactive molecules fixed on the surface: visible light living graft polymerization system is used to realize the immobilized enzyme on the surface as well as the cell surface modification to improve the stability. Finally, their recent advances in the biomedical fields and the future opportunities and challenges are highlighted.关键词：Photo-initiated living graft polymerization;Surface modification;Antibacterial;Immunoassay;Bioactive molecular
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发布时间：2021-03-05
Feature Articles
- 摘要：Lithium ion batteries (LIBs) generally suffer from severe electrolyte decomposition and the unstable cathode and electrolyte interface (CEI) during high voltage cycling, seriously impeding their practical applications. Binders can not only tightly bind the cathode active materials and conductive carbons onto the current collector, but also play a positive role in the construction of multi-scale compatible CEI. Thus, theoretically, the optimization of binders can effectively solve the above problems. In this review, we present the requirements of high voltage cathode binders, including excellent adhesion and mechanical properties, electrochemical stability and thermal stability, as well as good ion and electron transport capacity, review the high voltage cathode binders reported at present through natural binders and synthetic binders and summarize the recent research progress and development status of binders for high voltage LIBs along with the action mechanisms of various binders on the bonding and coating of electrodes and the performance of LIBs. Furthermore, we elaborate the interactions between the polar groups of binders and the cathode active particles, such as hydrogen bonding and ion dipole interaction. Finally, some perspectives and directions on future development of state-of-the-art binders for high voltage LIBs are discussed.关键词：Lithium ion battery;High voltage cathode;Binder;Natural binder;Synthetic binder
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发布时间：2021-03-05 - 摘要：In recent years, the utilization of biomedical materials causing iatrogenic infection problems has emerged as a serious threat to people’s health. Fabrication of antibacterial coatings on the biomedical material surfaces is the key strategy to avoid such incident. Antibacterial coatings can eliminate initial bacterial attachment and prevent subsequent biofilm formation, which are essential in many biomedical applications, especially implanted medical devices. Presently, antibacterial coatings can be divided into four kinds based on their mechanisms and functions. They are adhesion coatings with bacterial killing function, anti-adhesion coatings with only bacterial inhibition function, anti-adhesion coatings with bacterial killing function and intelligent antibacterial coatings. Fabrication of antibacterial coatings on the biomedical material surface not only brings about excellent antibacterial properties, but also confers anti-adhesion, biocompatibility, oxidation resistance properties, as well as biological recognition and sensing properties to the materials. Although various approaches, including bacteria-inhibition and bacteria-killing mechanisms, have been developed, none has been entirely successful due to their inherent drawbacks. Here, we present the different antibacterial coatings, their fabrication methods as well as their corresponding applications in the various biomedical materials, such as implants and forin vitro usages. The design principles of these coatings are discussed and a brief perspective on remaining challenges and future research directions are presented. We believe that this review will provide a promising inspiration for further development of high-performance antibacterial coatings especially their applications in biomedical materials.关键词：Surface modification;Anti-adhesion;Antibacterial coatings;Biomedical materials
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发布时间：2021-03-05 - 摘要：Fluorescence correlation spectroscopy (FCS) is a statistical spectroscopy technique mainly used to study the dynamics of systems under thermal equilibrium. This technique is extremely sensitive and has excellent spatial and temporal resolution, making it very powerful in studying the dynamics of systems under thermal equilibrium, especially measuring translational diffusion of single molecules, in solutions and at interfaces. In recent years, there have been significant contributions of FCS to the investigations in the field of materials and chemistry researches, and a large number of new researches have been successfully conducted. In polymer science, this technology plays increasingly important roles, especially in polymer structure and dynamics. This review will cover many aspects of FCS, including the principles of FCS, the basic theory and the instrumentation of FCS. Experimental skills have also been introduced. Attention is paid to the applications of FCS in a few fields that are challenging to conventional methods such as dynamic scattering. The investigations by FCS have been introduced into polymer solutions, including polyelectrolyte solutions and cononsolvency of neutral polymers, and lateral diffusion of single polymer molecules at surfaces and interfaces, as well as the coupling of translational diffusion among charged macromolecules. It has been demonstrated that due to the extreme sensitivity, the FCS experiments are conducted at extreme dilution, making effective measurements of individual charged molecules and providing important information on the chain conformation and its transition. The advantage of FCS has also been shown to creat long enough time window for single molecule measurements. Under such conditions, diffusion of single polymer molecules can be measured while they are supposed to precipitate under experimental condition of conventional methods. The effectiveness of FCS in studying translational diffusion has also been demonstrated, showing the powerfulness of FCS in multiple dimensional measurements. All of the examples provided in the current review help to highlight the characteristics and advantages of FCS that distinguish it from other traditional technologies. It is believed that FCS can continue to enjoy its effectiveness in a number of fields in polymer researches.关键词：Fluorescence correlation spectroscopy;Polymer;Polyelectrolyte;Surface and interface;Cononsolvency
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发布时间：2021-03-05
Reviews
- 摘要：In order to obtain polymer composites with rapid self-healing function of thermal conductivity and mechanical strength degradation, a self-healing polymer reinforced by thermally conductive fillers was proposed. In this work, the bis(3-aminopropyl) terminated polydimethylsiloxane (H 2N-PDMS-NH2) was modified by introducing 6-methyl-4-pyrimidinone (UPy) as end groups, which was based on the reversible cleavage and reconfigurability of the quadruple hydrogen bonds between the UPy groups. The results of Fourier infrared spectroscopy (FTIR), mechanical tensile tests and scanning electron microscopy (SEM) showed that the UPy double-terminated polydimethylsiloxane (UPy-PDMS-UPy) had good self-healing properties, and the healing efficiency of mechanical strength reached 86.6% after healing at 60 °C for 20 h. Subsequently, thermally conductive composite material with self-healing function was prepared by filling hydroxylated boron nitride (mBN) into the UPy-PDMS-UPy. It was found that mBN could enhance the tensile strength of the composite material but reduce the toughness, and had positive and negative effects on thermal conductivity and self-selfing function, respectively. When the mBN content was 30 wt%, the tensile strength healing efficiency reached 82.0% after 40 h at 60 °C. And the thermal conductivity reached as high as 2.579 W·m−1·K−1 but fell with further increase of mBN content due to the aggregations and holes. Therefore, mBN-30/UPy-PDMS-UPy was involved in the following measurements. Infrared thermal imaging camera showed that the upper surface temperature of mBN-30/UPy-PDMS-UPy was close to the initial temperature after healing for 10 h, which showed good self-healing function of heat transfer, and the relevant self-healing machnism was discussed in the end. The design achieved the self-healing function of both mechanical strength and thermal conductivity for composite material, which provided a great guide for the design of self-healing thermal interface materials.关键词：Self-healing;Quadruple hydrogen bonds;Thermally conductive;Polydimethylsiloxane;Composites
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发布时间：2021-03-05 - 摘要：In recent years, non-conjugated aggregation-induced emission (AIE) polymers without traditional
${\text{π}}$ 关键词：Aggregation-induced emission;Non-conjugated polymer;Hydrothermal reaction;Ion detection- 178
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发布时间：2021-03-05 - 摘要：The alternating regulation of living anionic copolymerization of 1-(4-dimethylsiloxphenyl)-1-styrene (DPE-SiH) and isoprene (Ip) was studied. By combining in situ 1H-NMR with MALDI-TOF MS technologies, the sequence distribution and apparent rate constant of monomers in the copolymer, as well as the reactivity ratio of Ip were determined. The results showed that the amount of DPE-SiH unit entering in the copolymer was less than that of Ip, and the site of DPE-SiH unit was mainly gathered at the end of copolymer when without the addition of regulators. Meanwhile, the gradient copolymer was obtained with the reactivity ratiorIp=9.28. The apparent rate constants of DPE-SiH and Ip unit were KD=0.00134 min−1 and KIp=0.01421 min−1, respectively. In addition, the sequence distribution characteristics of the two monomers in the copolymer chain after the addition of the regulators [N'N'N'N-tetramethylethylenediamine (TMEDA) and potassium tert-butoxide (t-BuOK)] were investigated. The copolymer with the alternating sequence feature was obtained when the regulator TMEDA andt-BuOK were added, achieving the sequence control of DPE-SiH and Ip unit in the copolymer chain. Meanwhile, the alternating entry of two monomers in the copolymer chain and the improvement of trans-1,4 Ip contents of copolymer were attributed to the “space-limited” living species resulted by the addition of regulators according to the results of Gaussian simulation.关键词：Living anionic polymerization;Alternating sequence control;1-(4-Dimethylsiloxphenyl)-1-styrene;Isoprene
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发布时间：2021-03-05 -
Effects of Linear Alicyclic Polyamide Chemical Structure on the Mechanical and Optical Properties 增强出版
摘要：The three kinds of linear alicyclic polyamides (LATPA) with different repeating units were studied by a combination of Nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FTIR), thermal analysis, X-ray diffraction (XRD). The influence of the side and terminal groups of the chain structure on the aggregation structure of materials was discussed. The mechanical properties and optical transparences of LATPA with different aggregation structures were also compared. The relationship between chain structure, aggregation structure, and mechanical and optical properties was established. The results indicated that the steric hindrance of the side group prevented the chains to get organized orderly and reduced the crystallinity of LATPA, moreover, increased the glass transition temperature (Tg) of the material. The polymer chains can be packed more regularly and the crystallization can be boosted if the terminal extender groups are flexible aliphatic segments. The aggregation structures directly affect the mechanical properties. All LATPAs with amorphous and microcrystalline structures have excellent optical transparency. The former has slightly higher transparency, while the latter has the highest tensile strength and modulus, which is the contribution of microcrystalline structures to mechanical properties.关键词：Linear alicyclic polyamide;Chain structure;Aggregation structure;Mechanical properties;Optical transparency- 264
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发布时间：2021-03-05 - 摘要：Most of the traditional liquid crystal elastomers are based on polyacrylate or polysiloxane systems and prepared by thermal or photo-initiated free-radical polymerization. However, the free-radical polymerization is easily inhibited by oxygen, causing high volume shrinkage and large internal stress during the curing process . In order to address these drawbacks, we design and synthesize a new liquid crystal monomer and a crosslinking agent bearing epoxy groups. The epoxy liquid crystal elastomer is prepared by in situ cationic polymerization/crosslinking using iodonium salt as the photo-initiator. Compared with the traditional liquid crystal elastomers, the volume shrinkage is small during the photo-initiated cationic reaction and the photo-curing process will not be interfered by oxygen. The liquid crystallinity and mechanical properties of the epoxy liquid crystal elastomer material are systematically characterized. The results show that epoxy liquid crystal elastomer material prepared by photo-initiated cationic polymerization possess better mechanical properties than the traditional polyacrylate/polysiloxane liquid crystal elastomers. The elastic modulus reach 2.53 MPa at the temperature beyond the LC-to-isotropic phase transition.关键词：Liquid crystalline elstomer;Photo-initiation;Cationic polymerization;Reversible deformation
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发布时间：2021-03-05 - 摘要：Conductive polymer composites with positive temperature coefficient (PTC) effect have been widely utilized in electronic industry due to their low density, excellent processibility and abundant adjustability. At the melting temperature, the phase transition of crystalline region results in volume expansion, which leads to a dramatic increase in volume resistivity of the composite. Therefore, the PTC performances are highly correlated with the melting process and melt properties of polymer matrix, which means the motion ability of molecules chain during matrix melting affects the performances of the composite such as PTC intensity and reproducibility. Making a thorough inquiry of the effects of polymer molecular motility on PTC behavior is helpful for the design and fabrication of polymer based PTC materials with highly sensitive response to temperature and stable reproducibility in heating-cooling cycles. In this study, the resistance-temperature characteristic of carbon fibers (CF) filled poly(vinylidene fluoride) (PVDF) composites with varied melt viscosity of PVDF was investigated. All the samples showed significant PTC effect during heating processes without negative temperature coefficient (NTC) effect even at temperatures much higher than the melting point of polymer matrix. It can be found that the PTC transition temperature range depended only on the chemical structure and crystallinity of PVDF, while the cyclic stability of PTC behavior was significantly affected by the motion ability of the matrix molecules. For the PVDF(710)/CF composite with matrix of stronger molecular motion, during the heating cycles, the molecular chains possibly stuck to the fillers surface to form an insulating layer, which resulted in wider gaps between fillers and thus reduced tunneling current. After cooling, the reconstruction of conductive paths in composites was impeded, resulting in higher resistivity at room temperature, lower PTC intensity and worse reproducibility. On the contrary, in the PVDF(5130)/CF composites with higher matrix viscosity, the molecular chains with weaker motion ability would not cover CF particles. The composite could almost rebuild the conductive paths to the initial condition after heating-cooling cycles, thus stabilizing a better PTC reproducibility and stable resistivity at room temperature. When applied in the circuit overheat protection device, the PVDF(5130)/CF composite shut off the current timely at 167 °C and recovered the circuit when cooled down, exhibiting excellent sensitivity and reproducibility as thermal responsive switch.关键词：Poly(vinylidene fluoride);Conductive polymer composite;Positive temperature coefficient;Molecular motility
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发布时间：2021-03-05
Research Article
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