最新刊期
卷 54 ， 期 11 ， 2023
- 摘要：In nature, numerous adaptive polymeric gels with multiphase confined structures exist in biological soft tissues, such as anti-freezing gel in alpine biological cells and mechanical anisotropic gel in muscle tissue, which play an essential role in biological activities. Although synthetic gels have similar soft and wet properties and elastic characteristic to natural soft tissue, its application is limited in external complex environment due to the lack of adaptability. The adaptability of natural gel materials far exceeds that of current synthetic gels due to their special confined structures. Therefore, biomimetic design of heterogeneous confined structure is an effective approach to fabricating polymeric gel with high adaptability under various conditions. In this review, the design criteria and fabrication strategies of adaptive high-performance gels with multiphase confined heterostructures are reviewed. We summarized the research progress of polymeric functional gels in anti-freezing, shape memory, surface functionalization, high mechanical property and responsive actuation from three aspects: heterogeneous interpenetration network, microphase separation network and anisotropic network. Meanwhile, we also discussed the current challenges and prospects in the field of bioinspired confined adaptive polymeric functional gels.关键词：Bioinspired polymeric gel;Multiphase synthetic;Confined composite;Adaptive Function
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发布时间：2023-11-03 - 摘要：Stimuli responsive block copolymer nano-objects enable morphology and/or size transformations under certain conditions, which are widely used in biomedical applications. The nano-objects are traditionally prepared via dialysis method of amphiphilic block copolymers, however, suffering from long time (>day) and low solid content (<1 wt%). Recently, polymerization induced self-assembly (PISA) has emerged as a rapid (~hours or less) synthetic strategy to nano-objects with high solid contents (10 wt%‒50 wt%) and diverse morphologies. Among living/controlled polymerization methodologies, reversible addition fragmentation chain transfer radical polymerization (RAFT) and ring-opening metathesis polymerization (ROMP) are mostly investigated and used in PISA. This review focuses on synthesis and applications of stimuli responsive nano-objects via PISA. By introducing the specific structure into the monomers, dynamic covalent bonding, enzyme, pH, CO2, redox, thermal and light responsive nano-objects are prepared via RAFT or ROMP PISA. In response to the external stimuli, the morphology and/or size transformations are observed, which provide promising opportunities in biomedical applications, such as controlled drug release or gene delivery. Although remarkable advances have been achieved, great challenges still remain for PISA-based stimuli responsive nano-objects. Powerful polymerization approaches should be utilized in PISA, such as combing orthogonal mechanisms and microreactor-based flow chemistry. Structure design should be deeply considered to provide more efficient stimuli responsive modes. Morphologies and/or size transformation process should be carefully investigated to advance the real applications of PISA-based stimuli responsive nano-objects.关键词：stimuli response;nano-object;polymerization induced self-assembly;Block copolymer
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发布时间：2023-11-03
Review
- 摘要：There are plenty of studies on block copolymers constructed by hydrogen bonding in the literature. However, the number of reports on the effect of steric hindrance on the self-assembled strictures of these systems is very limited. In this work, supramolecular block copolymers PS-b-P4VP(Ben)x and PS-b-P2VP(Ben)x were constructed by hydrogen bonding between the pyridine-containing block copolymers PS-b-P4VP and PS-b-P2VP, having similar molecular weights and volume fractions and the synthesized small-molecule carboxylic acid Ben, where x is the molar ratio of the hydrogen-bonding donor Ben to the acceptor P4VP or P2VP. The microphase-separated structures of the hydrogen-bonding complexes were effectively controlled by adjusting the value of x. Fourier transform infrared spectroscopy (FTIR) was utilized to characterize the complexes obtained, confirming the formation of hydrogen bonding. Then differential scanning calorimetry (DSC) and wide-angle X-ray scattering (WAXS) were used to investigate their phase behaviors. The glass transition temperatures of the supramolecular blocks were found to decrease with the increase of x. Neither P4VP(Ben)x nor P2VP(Ben)x exhibited liquid crystallinity. Finally, small-angle X-ray scattering (SAXS) was used to explore the microphase-separated structures of the two types of hydrogen-bonding complexes. And the effect of the steric hindrance during the formation of hydrogen bonding on the nanostructures of the hydrogen-bonding complexes was summarized by drawing the phase diagrams. This work provides the basis for effectively controlling the microphase-separated structures of supramolecular block copolymers.关键词：Hydrogen bonding;Mesogen-jacketed polymer;Block copolymer;Steric hindrance;Microphase separation
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发布时间：2023-11-03 -
Synthesis of Pyrene Based
α -Diimide Nickel Catalysts for Ethylene Polymerization/Copolymerization 增强出版摘要：The transition metal catalysts required for coordination polymerization to prepare polyolefins have received high attention from academia and industry with the continuous development of the polyolefin industry. Among them, late transition metal catalysts represented by nickel and palladium have been widely studied in olefin/polar monomer copolymerization reactions due to their low oxygen affinity and high tolerance to polar groups. By selecting aromatic hydrocarbon groups with different structures, a series of late transition metal catalysts with different catalytic properties can be conveniently designed and synthesized. One of the structural characteristics of pyrene ring aromatic hydrocarbons is the π-π stacking effect between pyrene ring aromatic hydrocarbon molecules, which has the potential to regulate the performance of transition metal catalysts. This article introduced the pyrene ring group into the ligand structure and designed and synthesized a series of α-diimine nickel catalysts with pyrene ring structure, and the structures of these ligands and catalysts were characterized in detail by nuclear magnetic resonance spectrometer (NMR), electrospray ionization mass spectrometry (ESI-MS), X-ray diffraction (XRD), etc. Subsequently, the ethylene polymerization reaction of these catalysts was studied in heptane solvent. Due to the interaction of pyrene ring groups, the π-π stacking effect may be formed between these nickel complexes. In addition, adding pyrene molecules to the aggregation system may also form the π-π stacking effect with the complexes. By utilizing the π-π stacking effect of these pyrene ring based α-diimide nickel catalysts, the ethylene polymerization activity of the nickel catalysts was as high as 3.12×107 g·mol-1·h-1, with a weight average relative molecular weight of up to 1.98×106 g·mol-1 for the prepared polyethylene, and the branching degree of polyethylene was 4-77 C/1000 C. These catalysts can also achieve copolymerization of ethylene with methyl 10-undecanoate, with a copolymerization activity of up to 3.30×105 g·mol-1·h-1. Moreover, the copolymerization performance of 10-undecylenoic acid pyrene ester monomers with π-π stacking effect was better, which once again proved the possibility of π-π stacking effect in this type of catalyst.关键词：Nickel catalyst;Pyrene;Ethylene polymerization;Copolymerization;Polyethylene- 178
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发布时间：2023-11-03 - 摘要：The copolymer of ethylene and norbornene (NB) is the most representative cyclic olefin copolymer (COC). Introduction of NB imparts excellent strength, transparency, and heat resistance to COC, and it also makes it more brittle, which limits its application in many fields. Therefore, improving the toughness of COC while maintaining its excellent characteristics such as high strength, heat resistance, and transparency is a critical challenge. To address this challenge, this study optimized two catalysts, Ph2C(Cp)(9-Ind)ZrCl2 and Et(Ind)2ZrCl2, which exhibit comparable polymerization activity but different selectivities toward NB in the E/NB copolymerization. We studied the coordination chain transfer polymerization of two catalysts under different polymerization conditions to verify the reversibility of chain transfer of the two catalysts in E/NB copolymerization. Based on this, chain shuttling copolymerization of ethylene and norbornene by adopting a dual-catalyst system and Et2Zn as a chain shuttling agent was successfully achieved. The multiblock structure of the chain shuttling copolymers with both high and low NB incorporation in COC segments was further revealed by 13C-NMR spectra, GPC and DSC analyses. The molecular weight and composition of the multiblock COCs could be easily regulated by varying the amount of Et2Zn and initial monomer ratio. Thermodynamic, tensile, and light transmittance tests demonstrated that the multiblock COCs bearing significantly enhanced toughness (i.e., elongation at break increases from <5% to 10%-11%) compared to those of the random COC by single catalyst, while maintaining high strength, heat resistance, and light transmittance. In summary, a series of multiblock COCs were efficiently prepared via chain shuttling copolymerization by using a dual-catalyst system. As expected, these COCs exhibited enhanced toughness while maintaining high thermal resistance, mechanical strength, and transparency. This study offers a new solution for improving tensile performance while maintaining high heat resistance and transparency of COCs.关键词：Cyclic olefin copolymer;Chain transfer polymerization;Multiblock copolymer;Chain shuttling copolymerization
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发布时间：2023-11-03 - 摘要：A series of polyetherimides (PEI-TAn) with different contents of TA structural units were prepared from amino-terminated aniline trimer (TA), bisphenol A type diethyl dianhydride and 4,4'-diaminodiphenyl ether by changing the feed ratio. In order to analyze the effect of introducing electroactive aniline trimer into PEI on material properties, PEI/TAn blends with different TA contents were prepared. The structure, thermal stability, glass transition temperature and dynamic mechanical properties of PEI-TAn were studied by Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), 1H nuclear magnetic resonance (1H-NMR), thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The surface and volume resistivity of the copolymers and blends doped with dodecylbenzene sulfonic acid were compared and analyzed by using a surface/volume resistivity analyzer. It is found that the 5% thermal weight loss temperatures of the PEI-TAn are in the range of 417‒513 ℃, and the glass transition temperatures measured by DMA are about 237‒240 ℃, which imply that PEI-TAn have excellent thermal stability; The Young's modulus and elongation at break of the PEI-TAn films are in the range of 1.5‒2.3 GPa and 3.9%‒5.7% respectively. The dielectric constant and dielectric loss at 10 GHz are in the range of 2.7‒3.5 and 0.007‒0.013 respectively. The surface and volume resistivity of the PEI-TAn copolymer films are in the order of 107‒109, which is 7‒9 orders of magnitude lower than that of the PEI without TA structural unit, while the surface and volume resistivity of the PEI/TAn blend films is only 1‒2 orders of magnitude lower. The results show that polyetherimides with excellent performance and adjustable resistivity can be obtained by introducing electroactive TA units into the molecular structure of PEI.关键词：Polyetherimide;Aniline Trimer;Structure-Performance;Surface Resistance
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发布时间：2023-11-03 - 摘要：The copolymerization of 10-bromo-1-decene (BrDC) with propylene and ethylene by the constrained geometry scandium complex {Flu-(CH2)3-NHC}Sc(CH2SiMe3)2 was examined. The microstructures and thermal properties of the obtained polymers were characterized by NMR, GPC and DSC. The polymerization of BrDC within 60 min at room temperature afforded atactic homopolymer with high molecular weight (Mn = 6.50×104 g·mol-1) in 91% yield. The copolymerization of BrDC and propylene under 0.2 MPa of propylene was also successfully achieved at room temperature. The copolymerization activity reached up to 106 g of polymer·(mol of Sc)-1·h-1. The propylene-BrDC copolymers with controllable compositions (BrDC content = 1.1 mol%‒18.0 mol%), high molecular weight (Mn = 1.35×105‒1.88×105) were conveniently obtained by changing the feed of BrDC. The random propylene-BrDC copolymers contained isolated BrDC and atactic polypropylene blocks. The propylene-BrDC copolymers with different compositions possessed glass transition temperatures (Tg) in the range from -7 ℃ to -33 ℃. The scandium complex also showed high activity (106 g of polymer·(mol of Sc)-1·h-1) for the terpolymerization of BrDC with propylene and ethylene. The random ethylene-propylene-BrDC copolymers with controllable compositions (ethylene content = 37.8 mol%‒75.2 mol%, BrDC content = 2.3 mol%‒12.2 mol%) and high molecular weight (Mn = 2.31×105‒3.27×105) were obtained at room temperature. The ethylene-propylene-BrDC terpolymers with different compositions possessed glass transition temperatures (Tg) in the range from -43 ℃ to -59 ℃. When the ethylene content was higher than 67.0 mol%, the ethylene-propylene-BrDC terpolymers showed a melting point of 100 ℃.关键词：Scandium;Rubber;Polyolefin;Copolymerization;Brominated
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发布时间：2023-11-03 - 摘要：With the development of smart technology and wearable sensors, the requirements of the flexible sensors become higher and higher on stretchability and fit to human skin. The ionic gels can precisely match these demands and therefore attracting widely attentions. Comparing with traditional ionic gels, deep eutectic solvent (DES) ionic gels have the advantages on simple preparation process, high purity, low price, and have become a current research hotspot. However, their mechanical strength still need to be improved. In order to improve the mechanical properties of current conductive ionic gels sensing materials, an organic ionic hydrogel with high tensile strength based on betaine, itaconic acid, acrylamide and bacterial cellulose was fabricated in this work. The mechanical and sensing properties of the conductive ionic gels and their practical applications in the field of human movement monitoring were investigated. Due to the introduction of bacterial cellulose, the tensile strength of the ionic gel increased from 246 kPa (without BC added) to 689 kPa, which was 2.8 times comparing with that of the original gel. The resulting sensor can be used for strain detection. The gauge factor (GF) was 0.97 in the tensile strain range of 0%-75%, and 1.417 in the range of 75%-150%, 1.729 in the range of 150%-200%. The responsive time was around 230 ms. The cyclic stretching experiments run over 1000 times under 50% of strain, suggesting that the sensor has good working stability. Meanwhile, this conductive ionic gel exhibited transmittance up to 87.64% at a thickness of 2 mm. It can be applied to the human skin surface to accurately monitor various body movements, including finger, elbow, wrist, knee and other joint bending, which has broad prospects in the field of smart wearable equipment and medical therapy. Meanwhile, the sensor can also be used to detect various movements of robot, suggesting it potential in automatic controlling and artificial intelligence.关键词：Deep eutectic solvents;Bacterial cellulose;Flexible sensor;Conductive ionic gel
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发布时间：2023-11-03 - 摘要：The application of biodegradable polymer fibers in the disposable fabrics, such as masks, protective clothes and courier packaging, is one of the effective pathways to solve the environmental pollution issues originating from waste fabric. However, improving the hydrolysis resistance of biodegradable fibers during storage and usage process plays a key role in determining the application of the biodegradable fibers. In this study, the poly(p-dioxanone) (PPDO)/cellulose nanofibers (CNF) fibers with excellent hydrolysis resistance were prepared by spinning and stretching. After spinning and stretching, the CNF will orient along the stretching direction, and therefore orderly distributing in the amorphous region of the PPDO fiber, resulting in obvious restriction for the diffusion rate of the water vapor. Compared to the pure PPDO fibers with the same preparation conditions, the PPDO/CNF fibers have been significantly improved in performance retention during stored at 25 ℃ and 60% humidity. After 8 weeks of storage, the breaking strength of the PPDO fibers decreased from (146.0±6.4) MPa to (27.3±4.8) MPa, completely losing the knotting strength. In comparison, the breaking and knotting strengths of the PPDO/CNF-2.0 wt% fiber only decreased from (162.9±7.0) MPa and (129.1±19.4) MPa to (105.5±12.7) MPa and (78.0±4.1) MPa, respectively, which are equivalent to 64.8% and 60.4% of the fibers before hydrolysis, and therefore could still meet application requirements. This work provides a simple and effective strategy for both improving the hydrolysis resistance and mechanical properties of PPDO fibers.关键词：Poly(p-dioxanone);Cellulose nanofibers;Hydrolysis resistance;Mechanical properties
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发布时间：2023-11-03 - 摘要：Under relatively stable fabrication conditions of the recycled pulp (RP), significant fluctuations in the degree of polymerization (DP) of the RP inevitably occurs due to the inherent batch to batch differences in waste cotton textiles. In order to invetigate the influence of the DP of recycled cotton pulp on its Lyocell spinning process and fiber mechanical properties, a series of recycled cotton pulps with different DP (from 300 to 1172) were prepared by adjusting the fabrication process of RP. Furthermore, the effects of DP on the solubility of RP in N-methylmorpholine-N-oxide, the spinnability of corresponding spinning solutions, and the mechanical properties of the regenerated Lyocell fibers were firstly investigated. Results showed that the solubility of the RP with low DP (300‒725) was good and that with higher DP (1172) was relatively poor. As for the spinnability of corresponding spinning dope, the RP with significantly low DP (DP 300) shows relatively poor spinnability, while the RP with severely high DP (DP 1172) cannot be used for spinning. Those with appropriate range of intermediate DP can be used for continuous and stable spinning. In addition, the dry tensile strength (3.35‒4.72 cN/dtex) and modulus (70.9‒146.19 cN/dtex) of the regenerated Lyocell fibers were significantly improved as the increase of DP ranging from 300 to 725. Overall, the regenerated Lyocell fibers prepared from the RP with DP 578 and DP 725 present excellent mechanical properties similar to those of the Lyocell fibers fabricated from commercial COSMO wood pulp. An appropriate DP range of recycled cotton pulp suitable for Lyocell spinning utilization was obtained. This is expected to provide valuable guidance for industrial application of recycling waste cotton textiles to fabricate Lyocell fibers with high-performance.关键词：High value recycling of waste textile;Recycled pulp from waste cotton textiles;Degree of polymerization;Lyocell fiber;Spinnability
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发布时间：2023-11-03 - 摘要：Polymer complexes exhibit environmental-responsiveness owing to the integration and assembly of stimuli-sensitive components, leading to the changes in their structure or properties. Humidity is one of the general environmental parameters which can influence the fabrication and application of polymer complexes, and thus it is important to investigate the effect of humidity on the structure and properties of polymer complexes. Herein, three hydrogen-bonding complex fibers were constructed using poly(acrylic acid) (PAA) as a hydrogen-bonding donor, and polyvinylpyrrolidone (PVPON), poly(2-ethyl-2-oxazoline) (PEOX) and poly(ethylene oxide) (PEO) as the hydrogen-bonding acceptors. Results show that the strength of hydrogen-bonding complexation affects the morphology and glass-transition temperature of the prepared complex fibers. With the increase in humidity, PAA/PVPON fiber stayed in a glassy state while PAA/PEOX fiber presented a glass-transition-like behavior at high humidity. As for PAA/PEO fiber, it showed a rubber-like transition behavior even at low humidity. It is found that the mechanical properties of the complex fibers are different mainly attributed to the different complexation strengthes, chain structures and water contents in the systems. The storage modulus-frequency master curve of polymer complex under humidity field was constructed using time-humidity superposition technique through dynamic mechanical multi-frequency strain test, and the mechanical relaxation in a wide time range was presented. Above all, this work can provide basic guidance for constructing humidity-response materials and analyzing the service capability of polymer complex materials.关键词：Polymer complex;hydrogen-bonding complex;humidity;Mechanical property;time-humidity superposition
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发布时间：2023-11-03 - 摘要：Molecular dynamics simulations were used to investigate the micro-mechanism of the excellent load-bearing and lubrication properties of konjac glucomannan (KGM) solutions. The formation process of the KGM hydration layer was elucidated, and the load-bearing capacity and shear characteristics were explored under simulated conditions (pressure range: 0‒1000 MPa, shear velocity range: 0.02‒1 nm/ps). The lubrication mechanism of KGM was also revealed in this work. The simulation results revealed that the KGM molecules in the solution form hydrate molecules with water molecules through hydrogen bonds. Due to the adsorption effect, these hydrated molecules aggregate on the surface of the iron atoms to form a hydration layer, which serves as a pressure-bearing carrier. In the shear process, KGM hydrated molecules absorbed on interfacial face weaken the interaction between water molecules and irons, which reduce the interfacial shear stress. When the number of KGM is too large, the concentration of KGM molecules in the middle position of liquid phase increases, the flow drag of liquid phase layer increases, which results in larger interfacial shear stress. The hydrogen bond action between KGM molecules and water molecules weakens with the increase of shear velocity, and the constraint on water molecules by KGM hydrated molecules reduces, which makes interfacial shear stress increase with the increase of shear velocity.关键词：Molecular dynamics simulation;Konjac glucomannan;Loading mechanism;Lubrication mechanism
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发布时间：2023-11-03
Research Article
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