最新刊期
卷 51 ， 期 7 ， 2020
- 摘要：By confining the polymerization in nano-sized reactors, Prof. Hu and coworkers from East China University of Science and Technology demonstrated a novel strategy to control molecular weights with a narrow polydispersity.关键词：Stepwise polymerization;Controllable;PDI
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发布时间：2021-01-26 - 摘要：Semi-aromatic polyamides (SaPAs) and their derivatives combining each advantage of aromatic and aliphatic polyamides receive ever-increasing interest in both academic and industrial fields. However, severe challenges, such as processibility and flammability of SaPAs still remain which limit their versatile applications. In order to endow satistied processibility of SaPAs either in melt or in solution, tremendous efforts have been explored to weaken the interchain cohesive energy by chemical modification of the SaPAs’ backbones or side groups. Unfortunately, their flame retardancy got even worse. In this work, a novel series of SaPAs containing flexible siloxane spacers and rigid fluorenyl pendent, termed P-FPH100−xSix, were designed and synthesized through the aromatic nucleophilic substitution (SNAr) polycondensation. The effects of both the fluorenyl pendent and siloxane spacers on the comprehensive properties of the semi-aromatic polyamides were comprehensively investigated. On the one hand, the presence of the rigid fluorenyl pendent endowed the resulting P-FPH100−xSix with enhanced thermal stability and mechanical properties, compared with the commercially available HTN. On the other hand, with increasing content of the siloxane spacers, their tensile strength and impact strength gradually decreased. Most importantly, by introducing the silaxane spacers, P-FPH100−xSix displayed intrinsic flame retardancy and anti-dripping performance despite the absence of conventional P-/N-containing flame retardants. When the content of the siloxane spacers was 10 mol%, the P-FPH80Si20 did not only achieve the V-0 rating in UL-94 burning test with limiting oxygen index (LOI) as high as 33.5%, but also maintain 80.0 MPa of tensile strength and 4.8 kJ/m2 of the notched Izod impact strength. Taking the aforementioned advantages, this kind of novel SaPAs hold potential in a wide range of applications.关键词：Copolyamide;Siloxane spacer;Mechanical properties;Flame retardancy
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发布时间：2021-01-26 - 摘要：Giant molecules are a new type of precise polymers whose building blocks are rather rigid molecular nanoparticles, e.g. polyhedral oligomeric silsesquioxane (POSS). Giant molecules containing a large number of molecular nanoparticles connected in 3-dimension have persistent 3-dimensional shape, and are different from traditional chain-like polymers. We studied a series of hydrophilic giant molecules and associated clusters of hydrophobic giant molecules. Their dynamics in the bulk state, above their glass transition temperature (Tg) is governed by their diameter, unlike the dynamics of traditional polymers which is governed by entanglement. The relaxation of giant molecules slows down by at least 108 when their diameters increases across the critical diameter. Giant molecules that are larger than the critical diameter cannot relax or diffuse. The exhibited elastic modulus plateau is proportional to temperature, corresponding to the confinement on individual “nanoatom”. 3-Dimensional giant molecules exhibit new rules other than reptation, entanglement, and tube in traditional polymer, and may bridge polymers and colloids. Random First Order Transition theory derived that, at the onset of glass transition, cooperative rearranging regions are 6 times the diameter of basic moving units. This is in accordance with our results. We claim large giant molecules are in a glass-like state, namely cooperative glass. Soft clusters such as giant molecules may resemble the cooperative rearranging region, thus experimentally supporting deeper understanding on glass transition.关键词：Giant molecules;Rheology;Dynamics;Soft-cluster;Cooperative glass;Entanglement
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发布时间：2021-01-26 - 摘要：Structural proteins from nature are fantastic macromolecules. Based on the folded/unfolded structures and supramolecular interactions, the assembled biomaterials exhibit very promising applications in high-tech fields due to their extraordinary mechanical performance. However, present study is focusing on the proteins of spider silk and silkworm which leads to the limited choice for the design and synthesis of artificial proteins. It is also difficult to optimize the structures of artificial proteins due to the incomplete/destroyed functional domains. Moreover, it is challenging for mass production of the proteins when they are expressed in heterologous hosts. Therefore, the realization of rational design of structural proteins, efficient biosynthesis, precise assembly from molecule to bulk materials, and the optimized mechanical performance is still a major challenge. Nowadays, synthetic biological technology as a powerful tool offers new opportunities for the development of artificial proteins and mechanomaterials. In this review, we outline recent progress and challenges in the design and synthesis of artificial proteins based on spidroins and non-spider sequences. We first briefly discuss the structure, composition, mechanical modulation, and application of protein-based fibers. Next, an overview of the synthetic protein-based adhesives is given. Finally, the development of protein-based structural biomaterials is prospected. The achievements in development of structural proteins by synthetic biology certainly will accelerate the protein-based mechanomaterials for translational applications.关键词：Structural proteins;Synthetic biology;Mechanical performance;Fiber;Adhesive
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发布时间：2021-01-26 - 摘要：High-performance electrolyte is necessary to improve safety issues and electrochemical performance of rechargeable lithium batteries. Sandwich-structured electrolyte, a novel class of electrolyte system, possess special two, three or more layers of symmetrical or asymmetrical structures, which can complement the performance advantages of different materials, effectively improving the performance of rechargeable lithium batteries. Based on this, this paper combs the multi-functional applications exhibited by sandwich-structured electrolytes in high-voltage lithium batteries, solid-state lithium batteries, lithium metal batteries and high-energy lithium-sulfur batteries: (1) enhancing ionic conductivity; (2) improving compatibility of the lithium/electrolyte interface to inhibit lithium dendrite growth; (3) improving the oxidation resistance of the electrolyte at the cathode interface; (4) preventing dissolution of transition metal ions in the cathode; (5) suppressing the shuttling of polysulfides to improve the electrochemical performance of lithium-sulfur batteries. And from the specific application of sandwich-structured electrolytes, we mainly summary the types, preparation process and research advances of sandwich-structured electrolytes in high-performance rechargeable lithium batteries. At the end of the review, we also discuss the challenges and future development of sandwich-structured electrolytes. It will undoubtedly act as a great reference and theoretical guidance for researchers engaged in high-performance electrolytes for rechargeable lithium batteries.关键词：Sandwich structure;Electrolytes;Rechargeable lithium batteries;Interfacial compatibility;Perspectives
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发布时间：2021-01-26 - 摘要：Exploring molecular interaction mechanisms is vital for a better understanding of life activities. In recent years, with the development of DNA nanotechnology, researchers have been using DNA nanostructures to study molecular interactions. Numerous progresses have been made on molecular interaction mechanisms using DNA nanostructures. With high programmability and addressability of DNA nanostructures, the system to be observed could be located on DNA nanostructures through different strategies such as DNA hybridization and covalent interactions. The spatial arrangement, molecule type, and the number of target molecules can be precisely controlled. Thus, DNA nanostructures offer an excellent template for observing molecular interactions. With the designability and high rigidity, DNA nanostructures could be utilized as frames with certain mechanical properties. By spatially organizing anchored molecules, nanoscale microenvironment could also be regulated on the platform of DNA nanostructures. In addition, DNA nanotechnology could be combined with various single-molecule techniques such as fluorescent imaging, atomic force microscopy, allowing single-molecule study with DNA nanostructures. In this review, we provide an overview of the construction of observing platforms with DNA nanostructures and the applications of DNA nanostructures in the study of molecular interactions. Finally, we summarize and prospect the development of DNA nanotechnology in this field.关键词：DNA nanotechnology;Molecular interactions;Single-molecule imaging
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发布时间：2021-01-26 - 摘要：Lysine and furfural are naturally available renewable resources. With the dwindling petroleum and eventual depletion of fossil resources, the controlled synthesis of bio-based polymers derived from lysine and furfural has recently become a growing research focus. However, their simple and general polymerization still remains a key challenge. Herein, we demonstrate that natural lysine and furfural monomers can be polymerized via Ugi reaction in a step-growth fashion, which leads to the polypeptoids with a number average molecular weight (Mn) up to 10.0 kg/mol, under mild conditions (open to air, room temperature, and catalyst free). More importantly, the polymerization can be carried out in water, avoiding the use of toxic solvents. The structures of resultant polypeptoids were confirmed by 1H- and 13C-NMR spectroscopy. All of the signals attributed to the repeating unit of the polypeptoid that should be produced by the Ugi reaction are visible. Moreover, the MALDI-TOF MS analysis of the resulting product consists of an array of peaks separated by a 407.2 Da interval, which corresponds to the molar masses of the repeating unit. The MALDI-TOF MS result is consistent with the proposed mechanism of Ugi reaction. These polypeptoids exhibit aTg value of 116 °C, and do not show melting transition. Indeed, the renewable feedstocks and simple concepts described here offer an attractive framework from which the Ugi reaction can be applied to prepare lysine and furfural based polymers.关键词：Ugi reaction;Lysine;Furfural;Renewable resource
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发布时间：2021-01-26 - 摘要：As one of the most important thermoplastic polymer materials, polypropylene (PP) is mainly flawed on mechanical properties by low impact strength (particularly at sub-zero temperatures) and on melt processibility by low melt strength, hindering greatly efforts that are aimed to expand its applications. It is thus of great scientific as well as practical importance to address these two issues simultaneously and to prepare both mechanical and processing-proof new PP materials. However, due to the long-standing challenge in propylene polymerization of long chain-branching, the past efforts succeeding in achieving increased impact strengths by heterophasic copolymerization incorporating elastomeric ethylene-propylene copolymer (EPR), have nonetheless failed to make progress in improving the processing side of properties. In this study, we introduce anα-alkenylmethyldichlorosilane-mediated heterophasic copolymerization approach to address the problem. By introducing heterophasic copolymerization of propylene, α-alkenylmethyldichlorosilane can promote resultant PP/EPR heterophasic copolymers to be long chain-branched by an additional facile hydrolysis treatment. Phase-separated PP impact copolymers with long chain-branched structure were prepared by the rendered heterophasic copolymerization of propylene, which were confirmed by GPC, rheology, as well as morphology (SEM) measurements. The LCBed PP impact copolymers simultaneously possess high melt strength and strong strain-hardening effect in extensional rheology test and high impact resistance in mechanical properties test, providing a new platform for developing advanced PP materials with all-round application adaptability.关键词：α-Alkenylmethyldichlorosilane;Heterophasic copolymerization of propylene;Long chain-branching;High melt strength;PP impact copolymer
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发布时间：2021-01-26 - 摘要：Poly(ethylene glycol) (PEG) has become the “superstar” in the field of biological materials due to its excellent biocompatibility. However, the molecular mechanism underlying its biocompatibility is still unclear. In this work, we have investigated the relationship between the biocompatibility and the bound water of PEG by single-molecule force spectroscopy (SMFS). To discern the effect of bound water on PEG in an aqueous solution, the single-chain inherent elasticity of PEG should be determined first as a reference. The inherent elasticity of PEG is obtained in a small-sized nonpolar organic solvent, nonane, which is confirmed by the quantum mechanical calculations-based freely rotating chain model (QM-FRC model). Then, SMFS experiments have been performed in phosphate-buffered saline (PBS) to study the effect of bound water on PEG. The shoulder plateau in the force-extension (F-E) curve of PEG obtained in PBS should be caused by the rearrangement of the bound water (water bridge) during the PEG elongation. This assumption has been confirmed by the two states QM-FRC model (TSQM-FRC model), which takes into account the effect of the water bridge. This bound water rearrangement will consume additional energy (Ew) besides that for the inherent elasticity of the chain. This Ew is calculated to be ~ 1.59 kBT/unit (3.93 kJ/mol) by integrating the area between the F-E curves of PEG obtained in PBS and nonane, closed to those of biomacromolecules. Inspired by the relationship between the low Ew and the behaviors of biomacromolecules, we have speculated the relationship between the biocompatibility and the bound water of PEG: (1) Like those of biomacromolecules, this Ew makes sure that the conformational transition of PEG in blood or cell will not consume (or produce) too much energy. Thus, the energy disturbance caused by PEG can be borne by the organism. (2) An appropriate Ew can prevent the aggregation of biomacromolecules and PEG. Biomacromolecules can self-assemble into the high-level structure after partial dehydration. If PEG has no bound water (Ew = 0), PEG may aggregate with the partially dehydrated biomacromolecules and then cause a series of consequences. In one word, the Ew closed to those of biomacromolecules may be an important factor for the excellent biocompatibility of PEG.关键词：Poly(ethylene glycol);Biocompatibility;Bound water;Single-molecule force spectroscopy
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发布时间：2021-01-26 - 摘要：Two-dimensional poly(vinyl alcohol) hydrogel (PVA 2DPCH) was prepared by using two-dimensional photonic crystal array of polystyrene as template and glutaraldehyde as cross-linking agent. Then the mercaptopolyvinyl alcohol two-dimensional photonic crystal hydrogel (PVA-SH 2DPCH) was obtained through thiolization modification of poly(vinyl alcohol) (PVA), with mercaptoacetic acid as esterifying agent. The response behavior of PVA-SH 2DPCH to Cu2+ was studied with the Debye ring method. The results showed that PVA-SH 2DPCH had a high-sensitive response to Cu2+. The gel shrunk in Cu2+ solution, and its Debye ring diameter (D) increased with increasing concentration of Cu2+. When the concentration of Cu2+ increased from 0 to 10−15 mol/L, its Debye ring diameter increased by 0.45 cm; when the concentration continued to 10−7 mol/L, its Debye ring diameter (ΔD) increased by 0.85 cm. To conclude, when the concentration of Cu2+ is in the range of 10−15 − 10−7 mol/L, the Debye ring diameter change (ΔD) of PVA-SH 2DPCH has a linear relationship with the concentration of Cu2+ (c), and the linear regression equation is ΔD = 1.195 + 0.0493 × logc, (ΔD (cm), c (mol/L)), R2 = 0.99899. With the prepared PVA-SH 2DPCH as a Cu2+ sensor, and the Debye ring method is adopted to characterize the concentration of Cu2+ in the solution. Featured by marker-free and visible detection, the Debye ring method is simple but highly efficient, which provides the possibility for real-time detection of Cu2+ in the field.关键词：Two-dimentional photonic crystal;Hydrogel;Determination of Cu2+;Chemical sensor;Thiolated polyvinyl alcohol;Debye ring
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发布时间：2021-01-26 - 摘要：The polymerization of 10-dimethylsilyl-1-decene (Decene-SiH) and its copolymerization with ethylene by the half-sandwich scandium complexes (C5Me4SiMe3)Sc(CH2C6H4NMe2-o)2 (1) and (C5Me4SiMe3)Sc(CH2SiMe3)2(THF) (2) have been examined. The microstructures and thermal properties of the obtained polymers were characterized by NMR, GPC and DSC. The copolymerization of ethylene with Decene-SiH under 1.01 × 105 Pa of ethylene has also been successfully achieved at room temperature. The copolymerization activity reached up to 105 g of polymer (mol of Sc)−1 h−1 and the conversion of Decene-SiH reached up to 99%. The ethylene/Decene-SiH copolymers with controllable compositions (Decene-SiH content = 8 mol% ~ 50 mol%), high molecular weight (Mn = 7.2 × 104 ~ 10.0 × 104) and narrow molecular weight distribution (Mw/Mn = 1.35 ~ 1.63) were conveniently obtained by changing the feed of Decene-SiH. When the content was less than 12 mol%, the isolated insertion of Decene-SiH into polyethylene chain was achieved. When the content was more than 26 mol%, the isolated and continuous insertion of Decene-SiH into polyethylene chain was also achieved. The ethylene/Decene-SiH copolymers with different compositions possessed a melting point (118 − 130 °C) and the copolymers possessed a glass transition temperature at −71°C when the Decene-SiH content of the copolymer was 50 mol%. The crystallinity of polyethylene decreased significantly with the Decene-SiH content of the copolymers. The “Si―H” group in the ethylene/Decene-SiH copolymers reacted with allyl glycidyl ether, N,N-dimethylacrylamide, p-N, N-dimethylaminostyrene and methyl methacrylate under the Karstedt’s catalyst. The conversion of “Si―H” groups reached 100%. Versatile functionalized polyethylene with hydrophilic properties were obtained by efficiently transforming the “Si―H” groups of the resulting copolymers into other polar groups.关键词：Scandium;Polyethylene;Functionalized;Copolymerization;Hydrosilylation
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发布时间：2021-01-26
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