最新刊期
卷 51 ， 期 8 ， 2020
- 摘要：Given their great biocompatibility, biodegradability and good mechanical properties, aliphatic polyesters as important polymers have been widely used in many applications as absorbable sutures, tissue engineering scaffolds and food packing materials. Aliphatic polyesters can be synthesized by ring-opening polymerization (ROP) of cyclic lactones or lactides. Organophosphazene bases are a family of uncharged, non-nucleophilic organobases, which have achieved great success as organocatalysts for the ROP of cyclic lactones and lactides. This feature article reviewed the recent progresses for ROP of cyclic lactones and lactides by utilizing phosphazene bases as catalysts, including γ-butyrolactone and its derivatives, ε-carprolactone, δ-valerolactone, lactide and macrolactones. The challenges and perspectives on the further development of phosphazene base catalyzed ROP were also discussed.关键词：Eco-polymers;Ring-opening polymerization;Polyesters;Organocatalysts;Phosphazene bases
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发布时间：2021-01-26 - 摘要：When polymer materials are damaged during usage, they will lose their original mechanical strength and function. Polymer materials with healability can have an extended service life, reduce raw material consumption and improve reliability. Endowing polymer materials with self-healing/healable capacity is an important requirement for the development of sustainable society. Polymeric complexes can be produced by directly mixing polymers with complementary interactions or copolymerization/sequential homopolymerization of two kinds of monomers with complementary interactions in bulk solutions. Polymer complexation provides a flexible method for the fabrication of polymer composite materials crosslinked by noncovalent supramolecular interactions or dynamic covalent bonds. Meanwhile, the mechanical properties of the polymeric composite materials derived from polymeric complexes can be conveniently tailored. This paper gives a comprehensive summary of the solution-based polymeric complexation method for the fabrication of self-healing/healable polymer materials developed in our research group. Based on the polymeric complexation method, we have successfully fabricated polymeric hydrogels, elastomers and high-strength polymer composites with excellent healing capacity. We also demonstrate that the contradiction between the satisfactory healability and high mechanical strength of polymer composites can be solved by integrating a high density of reversible supramolecular interactions andin situ-formed rigid polymeric complex nanoparticles in the targeted polymer composites. The polymeric complex nanoparticles can serve as nanofillers and cross-linkers to significantly improve the mechanical strength of the polymer composites. Meanwhile, the reversibility of supramolecular interactions facilitates the mobility of polymer chains and enables highly efficient healing of damaged composites to restore their original mechanical properties. Moreover, we also fabricated self-healing/healable polymer composite materials with functions such as antifogging, proton conduction and sensing. These polymer composite materials can heal mechanical damage as well as restore their original functions. We believe that the polymeric complexation method provides new avenue for the fabrication of self-healing/healable polymer materials with excellent mechanical properties and functions.关键词：Polymer complexes;Supramolecular chemistry;Self-healing materials;Non-covalent bonds;Supramolecular materials
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发布时间：2021-01-26 - 摘要：Topological proteins are proteins possessing non-linear backbones and nontrivial chemical topology. Since nascent polypeptide chains are strictly linear as defined by the translational mechanism of the cellular machinery, synthesis of topological proteins remains a huge challenge. By folding into various three-dimensional shapes, proteins can gain certain control over the spatial relationship of secondary motifs, however, the diversity of the chemical topology of the backbone remains largely untapped. The discovery of natural topological proteins in the past decades have inspired the researchers to explore the design and synthesis of artificial topological proteins. Meanwhile, the progresses in supramolecular chemistry and topological polymer chemistry have brought in various strategies for the synthesis of topological molecules in general. Among them, the “assembly-reaction” synergy seems to be a generally applicable and powerful one in creating unconventional structures. With genetically encoded entangling protein motifs and genetically encoded peptide-protein reactive pairs, different topological proteins have been prepared, including cyclic proteins, star proteins, branched proteins, tadpole proteins and protein catenanes. While structures and functions are well preserved in most cases, they also exhibit considerable advantages in terms of thermal stability and resistance to chemical denaturation and proteolytic digestion. Herein, begin with the major challenges in the synthesis of topological polymers, we summarize the biosynthesis of topological proteins in nature and the recent efforts to design and construct artificial topological proteins in chemistry. We will discuss the strategies for their synthesis and characterization, as well as the potential functional benefits of topological proteins. Finally, we will present our perspective on the challenges and opportunities of this emerging field.关键词：Topology;Protein engineering;Knot protein;Lasso;Catenane;Assembly-reaction synergy
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发布时间：2021-01-26 - 摘要：Polymer products are widely used in our daily life. While plastics make modern life very convenient, there also two concomitant issues that need to be addressed immediately. First, plastic waste generated from the use of polymer materials is destroying the living environment. In particular, thermosetting polymers cannot be reprocessed once the crosslinked network structure forms. However, by introducing “vitrimer” chemistry to thermosets, damaged thermosetting polymers can be repaired, their service life can be extended, and plastic waste will be reduced. Second, the preparation of polymer materials often requires the consumption of non-renewable petrochemicals, which in turn increases industrial pollution. The use of renewable resources to prepare polymer materials could be an effective solution to slow down the consumption of fossil resources and reduce associated pollution. To promote greener polymer production, this paper reviews the recent research progress on bio-based vitrimer materials. First, the history and unique features of vitrimer materials are reviewed. These unique features, including repairability, recyclability and reprocessability, originate from the dynamic covalent crosslinks which often exhibit both associative and dissociative mechanisms. Second, recent developments in vitrimer preparation from vegetable oil, lignin, cellulose, natural rubber, rosin, vanillin and other biobased resources were reviewed, and the commonly involved dynamic covalent chemistries were discussed.关键词：Dynamic covalent bond;Bio-based polymer;Vitrimer;Thermoset
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发布时间：2021-01-26 - 摘要：Understanding how complex inorganic materials are organized through synergistic self-assembly and chemical synthesis across multiple length scale using nanocellulose is of growing interest in materials science and nanotechnology. This review article highlights recent advances in the synthetic construction of nanocellulose-based inorganic materials. We first examine a range of inorganic cations that give rise to inorganics-coated nanocellulose. It shows that nanocellulose binds preferentially to the inorganic cations in the order of hard base ≥ borderline base >> soft base, indicating the formation of stable acid-base pairs between the surface hydroxyl oxygen of nanocellulose and the hard base closely followed by the borderline base. We then look into approaches that facilitate the nucleation, growth and transformation of inorganics surrounding nanocellulose. It is demonstrated that extended length scale structuration is possible, which warrants functional enhancement and renders new functionality for nanocellulose-based inorganic materials. Examples of function-led organization of nanocellulose-based inorganic materials were presented. Of particular interest are cellulose nanocrystals that facilitates its use as a chiral nano-mesogen for helicoidal organization with circular polarization ability, bacterial cellulose that promotes its applications as an optical sensing platform and cellulose nanofibers that exploit its potential as conductive substrates for water splitting. Ongoing research continues to exploit the richness of nanocellulose as a sustainable platform for rational organization of functional inorganic materials.关键词：Nanocellulose;Self-assembly;Synthesis;Multi-level and structural hierarchy;Rational organization
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发布时间：2021-01-26 - 摘要：Natural polymers are environmentally friendly and sustainable renewable raw materials with many advantages, such as variety of sources, different chemical components, excellent biocompatibility and biodegradability. The controllable production of conductive materials derived from natural polymers with excellent properties is critical for the design and manufacture of new conductive materials, and the assembly of unique functional flexible sensors. Recently, the research of green flexible sensors based on natural polymers has been widely concerned by scientists at home and abroad, and great progress has been made. The review summarizes the preparation approaches of conductive materials based on natural polymers, which can be divided into template method and doping method. The template method takes the micro-nano skeleton structures of the natural polymers as matrix, while the doping method takes the products or derivatives of the natural polymers as matrix. The research progresses of flexible sensors based on natural polymers are summarized, including the flexible sensors of humidity, temperature, strain, airflow, gas, light and biomedicine. Finally, the prospects of flexible conductive materials based on natural polymers in the design and assembly of flexible sensors are prospected, and novel ideas to efficient utilization of natural polymer materials for developing green flexible electronics have been proposed.关键词：Natural polymers;Conductive materials;Flexible sensors
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发布时间：2021-01-26 - 摘要：With the emphasis on the development and utilization of renewable energy, environmentally responsive hydrogels based on cellulose have attracted much attention with their structure design and response performance. Besides the good biocompatiblity and biodegradablity, cellulose-based environmentally responsive hydrogels show excellent abilities in detection, recognition and response behaviors to environmental and biomedical relevant stimuli, which expands the applications of these hydrogels as biomedical smart materials and in other fields. In this article, we summarized the design and applications of environmentally responsive hydrogels, where cellulose could work as the cross-linkage in the 3D network or the nanofillers to improve properties, especially mechanical properties of hydrogels. Classified by crosslinking methods including physical or/and chemical crosslinking, the structural design and fabrications of these cellulose-based hydrogels were first discussed. Physical cellulose-based hydrogels constructed by supramolecular interactions usually exhibited more flexibility, and their responsiveness to external stimuli might depend on changes among the interactions in networks, while the chemical hydrogels showed responsiveness due to the cellulose skeleton mostly like pH responsive carboxymethyl cellulose. Moreover, focusing on their properties and functions, several types of cellulose-based hydrogels and their responses to chemical, physical and multi-stimuli were described, such as pH responsive, redox responsive, CO2 responsive and temperature responsive hydrogels. Taking some biomedical researches as examples, it was expounded in this paper that the environmentally responsive hydrogels based on cellulose could be applied as drug delivery carriers, shape memory devices and wound dressing, etc. To broaden the use of environmentally responsive cellulose-based hydrogels, it’s of great importance to design the hydrogel networks with multiple responsiveness and to improve the speed and sensitivity of the response process. With the development of artificial intelligence, it’s believed that environmentally responsive cellulose-based hydrogels will have great potential in applications for 3D printing, electronic skins, intelligent soft robots and so on in the future.关键词：Cellulose;Hydrogels;Environmentally responsive;Stimuli-responsive;Smart materials
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发布时间：2021-01-26 - 摘要：The fibrinogen nanofilm was prepared by using the reaction between fibrinogen and the reducing agent tris(2-carboxyethyl) phosphate hydrochloride (TCEP) and resultant amyloid-like aggregation. The kinetics of the reaction between fibrinogen and TCEP and the change of its secondary structure were investigated with optical characterization methods such as fluorescence spectrum and far ultraviolet-circular dichroism. The structure of the thin film was characterized by transmission electron microscopy. The concentration of fibrinogen, the pH value and concentration of TCEP buffer on the thickness of the film were investigated by atomic force microscope and optical ellipsometer. The film stability was characterized by atomic force microscopy. Finally, the antifouling ability of the film was measured by platelet adsorption and protein adsorption. The experimental result shows that by controlling the reaction conditions, the film thickness was controlled, and the film showed excellent stability in different environments. More important, the thin film showed certain resistance to platelet adsorption and model biofluid mixtures (e.g., fetal bovine serum, milk). Therefore, the fibrinogen amyloid-like aggregation film reported in this article is expected to be used as a new type of bio-based materials in anti-thrombosis, vascula stent coating, anti-fouling coating and other biomedical engineering fields. The idea of phase-transited protein with strong non-specific adsorption through amyloid aggregation into anti-fouling coatings that resist non-specific adsorption of other molecules can inspire us to explore more anti-fouling systems based on functional protein aggregation mechanism.关键词：Fibrinogen;Nanofilm;Bio-based materials;Surface modification;Amyloid
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发布时间：2021-01-26 - 摘要：Cisplatin (CDDP), as a traditional first-line chemotherapeutic drug, has been broadly used for the treatment of numerous solid cancers in the clinic. However, the treatment efficacy of CDDP is limited by a variety of issues, including enhanced efflux, increased detoxification capability, and improved ability of DNA damage repair of cancer cells. For example, the high level of intracellular glutathione (GSH) significantly decreases the cytotoxicity of CDDP through the formation of stable GS-Pt complex, which can be rapidly extracted from the tumor cells through an adenosine triphosphate-dependent glutathione S-conjugate export pump (GS-X pump). Therefore, the antitumor efficacy of CDDP can be upregulated by inhibiting the synthesis of GSH with drugs, directly depleting GSH with organic or inorganic nanoparticles, or neutralizing GSH through upregulating the level of reactive oxygens species (ROS) in the cells. Herein, the intracellular acidity-sensitive nanocluster (NCPGN-Pt+As) was developed to improve the antitumor efficacy, which was fabricated by the calcium phosphate (Ca3(PO4)2)-curing of CDDP-loaded poly(L-glutamic acid) nanoparticle (PGN-Pt) and arsenic trioxide (ATO). The optimal mass ratio of CDDP and ATO in NCPGN-Pt+As was determined to be 2:1 by the coefficient of drug interaction (CDI) between CDDP and ATO. NCPGN-Pt+As exhibited a nanosphere structure with a diameter of 129.8 nm. NCPGN-Pt+As showed prolonged blood circulation, evidenced by the increased half-life (t1/2β) and the area under the drug concentration-time curve (AUC0-t). Moreover, NCPGN-Pt+As demonstrated the reduced accumulation in the normal tissues and improved accumulation in the tumor. The intratumoral accumulations of CDDP and ATO were 5.7 and 3.9 times higher than those of the free CDDP+ATO group, respectively, which should be attributed to the enhanced permeability and retention effect. Upon entering the endosome, NCPGN-Pt+As decomposed and released PGN-Pt and ATO under the acidic conditions. CDDP was sustainedly released from PGN-Pt in the cells and maintained effective concentration. CDDP and ATO synergistically upregulated the level of intracellular ROS, which could kill tumor cells or enhance the efficacy of CDDP and synergistically inhibit peritoneal metastasis of ovarian cancer. At the same time, NCPGN-Pt+As was proved safe by the remained body weights of mice during the treatment period and normal levels of the liver- and kidney-related parameters after all treatments relative to free CDDP+ATO. Given its excellent efficacy and safety, this platform provided a uniquely effective strategy for the design of CDDP nanomedicines.关键词：Polymer nanomedicine;Arsenic trioxide;Calcium phosphate nanocluster;Intracellular drug delivery;Synergistic chemotherapy of cancer
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发布时间：2021-01-26 - 摘要：Based on the strategy of normal combustion carbonizaiton, highly crystalline structure of cellulose nanocrystals (CNCs) is expected to favor a conversion to char. Thus, graphene with stable carbon skeleton, phosphorous compound and solid acid metal ion are specifically introduced to hybridize with CNC as one integration system through covalent bonding and complexation. In this case, phosphorous compound and solid acid metal ion might play the roles of free radicals capturing and dehydrogenation/char-forming catalysis, respectively. Moreover, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide firstly reacted with graphene oxide (GO) to obtain phosphorus-containing GO (P-GO), while the CNCs were esterificated by maleic anhydride to give the nanoscaled products with carboxyl groups-coverd surface (CNC-COOH); subsequently, a novel flame retardant CNC/P-GO hybrid (CNC@P-GO) was prepared via the complexation of Fe3+ with carboxyl groups on the surface of P-GO and CNC-COOH. Compared with no char residue of individual CNC-COOH or P-GO in air atmosphere under high-temperature alone, the char of the CNC@P-GO hybrid with the equivalent ratio of CNC-COOH to P-GO as 2:1 could reach up to 37.6%, showing a graphitized continuous structure. When this kind of the CNC@P-GO hybrids was applied to promote flame retardant of bio-based polyester, only very low loading-level of 5 wt% could result in 17% char residue rate of CNC@P-GO-filled poly(butylene succinate) (PBS) in contrast to almost no char of neat PBS. At the same time, the peak heat release rate and total heat release dramatically dropped down by 71% and 66%, respectively. The predominant reduction of the combustion heat indicated an enhancement of fire safety, which was mainly attributed to the fact that the CNC@P-GO hybrid as flame retardant resulted in the formation of a dense and continuous carbon layer with high graphitization degree. Overall, this study enriches the ideas on the design of high-efficiency flame retardants derived from biomass resources and the fire-safety enhancement of bio-based polyester.关键词：Cellulose nanocrystals;Flame retardants;Poly(butylene succinate);Fire-safety;Combustion to char
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发布时间：2021-01-26 - 摘要：Cellulose nanocrystals (CNCs) are a class of sustainable renewable nanomaterials with many advanced features, such as biodegradability, biocompatibility, large specific surface area, and outstanding mechanical properties. They have attracted significant interest due to their fascinating self-assembly behavior. In this work, amino modified CNCs (CNC-NH2) were prepared by reacting CNCs with epichlorohydrin and then with ammonia. The structure, morphology and self-assembly behavior of CNC-NH2 in aqueous suspensions and solid films were investigated by UV-Vis spectroscopy, DLS, XRD, XPS, POM, AFM, SEM, TEM and rheology testing. The degree of substitution of amino groups was deternmined to be 0.048. CNC-NH2 showed a rodlike morphology with the length (L) of (180 ± 75) nm and width (W) of (13 ± 5) nm, and the average aspect ratio (L/W) was nearly 13.8. CNC-NH2 could be well dispersed in water and the ζ-potential was determined to be −28.0 mV, which could be stored for a long time due to the strong electrostatic repulsion. The chiral nematic liquid crystal was observed in the CNC-NH2 suspensions as the solid content increased up to 1.75 wt%. The CNC-NH2 suspensions displayed unique rheological properties, which were divided into three regions: isotropic, biphase and liquid crystal, with increasing solid content. Moreover, the evaporation-induced self-assembly (EISA) method was used to prepare CNC-NH2 films. It was found that the liquid crystalline structure of CNC-NH2 in colloidal suspension still maintained in the solid films. The iridescent color of the films could be tuned by the initial content of the suspension and the ultrasonic time. The iridescence and colored films were obtained only if the pitch length in the solid film was approximately that of the wavelength of visible light. This work provides a new way for the preparation of cellulose liquid crystal materials, and helps to understand the formation mechanism of the liquid crystal of the rodlike nanoparticles.关键词：Cellulose nanocrystals;Amino modification;Self-assembly;Liquid crystal;Iridescent film
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发布时间：2021-01-26 - 摘要：Cellulose gel is first prepared by ionic liquid dissolution and regeneration, and then, boehmite, an aluminum oxide hydroxide (AOOH), is incorporated into cellulose gel via in situ “sol-gel” method. After supercritical CO2 drying, the cellulose/AlOOH composite aerogel membranes (CAAMs) are prepared. Related properties are investigated by Fourier transform infrared spectrometry (FTIR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM) with energy-dispersive X-ray spectra (EDS), transmission electron microscopy (TEM), dynamic mechanical analysis (DMA), and microscale combustion calorimeter (MCC), and ignition tests. And the CAAMs are further characterized in terms of electrochemical stability and electrochemical performance in lithium-ion batteries (LIBs) and are compared to a commercial polypropylene separator membrane (Celgard 2400). The in-situ formed nanofibrous AlOOHs are overlapped with each other, creating a network structure and homogeneously distribution in the membrane, which endows the CAAMs with compact morphology and uniform pore structure with porosity around 83.9% and an average pore size about 23 nm. The results demonstrate that the CAAMs have excellent flame retardancy and show self-extinguishing behaviors, and the peak of heat release rate (PHHR), the heat release capacity (HRC), and the total heat release (THR) are significantly reduced. Compared to Celgard 2400 that are easily softened at high temperatures, the CAAMs have almost no dimensional change at 150 °C for 30 min and display excellent thermal stability. The CAAMs have superior affinity for the polar liquid electrolyte and therefore the CAAMs have higher uptake of liquid electrolytes of 350% and higher ionic conductivity of 3.1 mS/cm in contrast with 90% and 0.53 mS/cm for the polypropylene separators. LIBs assembled with the CAAMs show better electrochemical stability at a voltage below 4.7 V versus Li/Li +. The capacity retention was 90.2% after 100 times cycling tests and the specific discharge capacity was 80.7 mA h g−1 at a fast charge/discharge rate of 4 C/4 C, which were better than those of commercial polypropylene separators. To sum up, this novel cellulose based composite aerogel membrane has great potential for the development of highly safe LIBs.关键词：Cellulose;Composite aerogel membrane;Flame-retardant;Lithium ion battery
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发布时间：2021-01-26 - 摘要：Bacterial cellulose (BC) is a nano-size cellulose synthesized by Gluconacetobacter xylinus during its growth and movement. Due to its good biocompatibility and good mechanical property, BC has been widely studied and applied in biomedicine and tissue engineering. Gluconacetobacter xylinus is a kind of aerobic bacteria, which preferentially synthesizes a BC film at the gas-liquid interface. Aiming at the sensitive characteristics of oxygen demand ofGluconacetobacter xylinus, we referred the method of “solid-gas-liquid” three-phase interface formed on the interface of superhydrophobic nanomaterials in aqueous solution. Photolithographic silicon substrate with different micropillar structure on the surface were manufactured, and further evaporated a layer of heptadecafluorodecyltrimethoxysilane on the surface of silicon substrate, which made the silicon substrate superhydrophobic. Different sizes of medium with bacterial droplet sprayed on the silicon substrate through a sprinkling can, which made medium droplets were limited contact with the top of micropillar on the photolithographic silicon substrate to form a "solid-gas-liquid" interface, to solve the oxygen demand problem between ordered microstructure template and bacterial culture medium. Therefore, many micro-size fibers obtained due to the different sizes of droplet, including BC nanowire, BC wall, BC ball and BC network. When bacterial medium droplet rolling on pillar-structured photolithographic (~ 5 μL) formed BC nanowire between tips of two micropillar, large droplet (10 – 20 μL) formed BC wall between two micropillars, over 30 μL droplet formed BC network on micropillars. Furthermore, large droplet (10 – 20 μL) formed BC balls instead of BC network on large space (20 μm) vertical pillar-structured photolithographic silicon substrates, micro droplet (~ 1 μL) formed single BC ball on small space (5 μm) vertical pillar-structured photolithographic silicon substrates. In addition, HaCAT cells could culture on the BC network that means BC network synthesize in this way could capture adherent cells. Finally, challenges and opportunities of this BC synthesis method and its BC products toward future applications were discussed.关键词：Bacterial cellulose;Gluconacetobacter xylinus;Solid-gas-liquid interface;Cell capture
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发布时间：2021-01-26 - 摘要：Methyl methacrylate grafted natural rubber (MGNR) is one of the modified products of biology-based natural rubber (NR). The relatively high Mooney viscosity of pure MGNR restrict its applications. Thus, it is rarely reported as the main component of rubber products. In this paper, polar MGNR and non-polar NR were blended. The high flexibility of NR molecular chains effectively reduces the Mooney viscosity of MGNR, improving the processability of MGNR. Besides, fumed silica with Si―OH on its surface was added. On the one hand, silica forms bonded rubber with MGNR and NR chains. On the other hand, Si―OH on the surface of fumed silica interacts strongly with methyl methacrylate grafted on MGNR, and silica acts as a “bridge” to improve the compatibility between MGNR and NR. As the content of fumed silica increased, the tensile strength and elongation at break of MGNR/NR (40/60) blend gradually improved. When the content of fumed silica was 10 phr, the tensile strength of the blend was 31.2 MPa, which improved by 42.4% and 55.2% compared with those of the blend without fumed silica and the pure MGNR, respectively. Meanwhile, the elongation at break of the blend was 605%, raised by 28.9% and 93.9% compared with those of the blend without fumed silica and the pure MGNR.关键词：Methyl methacrylate grafted natural rubber;Natural rubber;Processing performance;Compatibility
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发布时间：2021-01-26
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