最新刊期
卷 53 ， 期 1 ， 2022
- 摘要：By rational design of DNA supramolecular hydrogel with high permeability, Liu and coworkers reported a novel strategy to repair a completely transected spinal cord injury in rats. After the treatment, the rats recover hindlimb function with newly formed neural networks. Therefore, it opens a new avenue for tissue regeneration.关键词：Hydrogel;Permeability;Tissue regeneration
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发布时间：2024-10-08
Research Highlight
- 摘要：With the rapid development of the field of nucleic acid self-assembly, DNA becomes a functional and programmable material with high degree of free operation and unlimited possibilities. DNA nanotechnology based on various assembly principles has been widely used in biosensing, nanomaterial engineering, medical diagnosis and molecular computers. Nanopore analysis is an emerging, very effective single molecular technique for gene sequencing, molecular identification, and physical/chemical property characterization. Recently, due to the unique advantages such as high resolution, high throughput and label-free signalling, nanopore also raises increasing attention in the research of DNA nanotechnology, and has been explored as a new analytical method for various nucleic acid recognition and self-assembly behaviors. Meanwhile, DNA nanotechnology also provides more diversified solutions to the technical bottleneck of nanopore sensing, such as using functional nucleic acids (Aptamer or DNAzyme) and enzyme-free nucleic acid circuits to enhance detection sensitivity and specificity. This monograph systematically reviews these cross-field research progresses of nanopore technology and nucleic acid self-assemblies, which aims to summarize and prospect relevant new ideas and methods for single-molecule molecular analysis, information index, genotyping and clinical diagnosis.关键词：Soild-state nanopore;Nucleic acid nanostructure;nucleic acid circuits;Label-free characterization
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发布时间：2024-10-08
Feature Article
- 摘要：The polymerization-induced self-assembly (PISA) has been developed as a versatile technique to prepare the block copolymer-based nano-objects. Compared with the traditional block copolymer-based self-assembly technology, the PISA technology is featured with a polymerization process and a simultaneous self-assembly process, as well as with well-controlled morphologies and high solid content (up to 50 wt%). These advantages have facilitated the large-scale production and application of the nano-objects. Based on the modification of various "living"/controlled polymerization mechanisms and the optimization of various formulations, the PISA technology has been well developed over the past decade. Correspondingly, the application of the PISA technology is also widely used. Up to now, several reviews on the morphology evolution of PISA technology have been presented. However, a comprehensive summary on the application of PISA technique is still needed. In this review, following with a brief introduction on the fundamental principle and the status of PISA technology, the application of PISA in nanocomposite materials, biomedical materials, batteries, functional coatings, Pickering emulsifiers, nanostructured membranes, hydrogels, luminescent materials, and other fields will be focused and summarized. This summary is hoped to depict a comprehensive outline of PISA technology in recent years and to prompt the development of the self-assembly technology in interdisciplinary field.关键词：Polymerization-induced self-assembly (PISA);Block copolymer;Nano-objects
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发布时间：2024-10-08
Review
- 摘要：Thiazoliums had been developed as a non-metal catalyst for bulk ring-opening polymerization (ROP) of cyclic esters, having the advantages of high stability, available for various monomers, and good controllability to polymerization. However, in order to achieve efficient catalysis under bulk polymerization conditions, fluorine-containing anions were generally used for preparing thiazoliums to promote the compatibility between catalysts and monomers, which was not conducive to the biosafety of the polymerization products. In this work, a built-in thiazolium chloride catalyst using mesoporous PS microsphere with high specific surface as the carrier was developed to achieve effective catalysis for ROP without introducing fluorine-containing anions. Through quaternization reaction between 4-methylthiazole and chloromethylated PS mesoporous microspheres (PS-CH2Cl), built-in thiazolium chloride ([Thi]Cl@PS) catalyst supported by PS mesoporous microspheres was prepared. According to optical microscope, scanning electron microscope (SEM), and BET measurement, the [Thi]Cl@PS (specific surface area 137 m2·g-1) with micron-size (50-250 μm, mean diameter 153 μm), regular sphere morphology and a large number of inside pores (pore volume 0.31 cm3·g-1, pore size 6.46 nm) were composed of compact accumulated nanoparticles. Based on FTIR and elemental analysis, the loading amount of thiazolium chloride in mesoporous PS microsphere was 0.67 mmol/g. Similar to the small molecular thiazolium catalysts, the [Thi]Cl@PS heterogeneous catalyst could selectively catalyze ROP of cyclic esters with relatively low steric hindrance (i.e., ε-caprolactone, δ-valerolactone, p-dioxanone, and glycolide). Based on kinetic studies for catalyzing ROP of ε-caprolactone, both the [Thi]Cl@PS and small molecular thiazolium catalysts show "slow initiation" characteristics and first-ordered dynamics after fully initiation. The similar monomer selectivity and kinetic mode between the [Thi]Cl@PS heterogeneous catalyst and fluorine-containing small molecular thiazolium homogeneous catalyst suggest that they have a similar catalytic mechanism. Besides, the polymerization rate constants obtained from kinetic curves after fully initiation indicated that the [Thi]Cl@PS has medium catalytic efficiency (0.75 h-1·mol-1·L) relative to fluorine-containing small molecular thiazolium catalysts, i.e., [Thi]PF6 (7.50 h-1·mol-1·L), [Thi]Tf2N (0.80 h-1·mol-1·L), and [Thi]BF4 (0.28 h-1·mol-1·L). Benefiting from the heterogeneous catalytic mode of [Thi]Cl@PS microspheres, it could be easily separated from the reaction system and recycled by dissolving the crude product in chloroform and filtration. Moreover, the recycled [Thi]Cl@PS was reused as catalyst for ROP, and showed similar catalyzing activity, compared to the original cycle. However, owing to the residual PCL in microsphere, both molecular weight and polydispersity of yield PCL with recycled catalyst exhibited slight increase, suggesting that the controllability of polymerization also decreased.关键词：Thiazolium;Heterogeneous;Catalyst;Ring-opening polymerization
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发布时间：2024-10-08 - 摘要：Polymeric films with three-dimensional porous structures have various advantageous properties, such as high specific surface area and ultra-lightweight. Reasonable structural design could be used to achieve the regulation and functionalization of complex porous structures. As the expectation for the diversified and advanced applications of porous polymers rises, making porous structure with complicated 3D pore morphologies has become new challenge for researchers in this area. Inverse emulsion-breath figure (Ie-BF) method is utilized to fabricate polymeric thin films with asymmetric multi-layered micro-porous structures. By casting inverse emulsions under humid environmental condition, ordered honeycomb-structured BF pore array is formed on the top surface, while disordered porous structure with differently featured pore sizes and pore arrangement can be flexibly formed in the bulk layer. Dynamic morphological manipulation on the fabrication of porous structures (including pore size & size distribution, array regularity and bulk layer pore morphologies) is facilely achieved by tuning the composition of the casting emulsion as well as the environmental conditions. By loading fluorescein isothiocyanate within the emulsion droplets and tracking the distribution of fluorescein isothiocyanate within the obtained Ie-BF film, the structure templating process of the emulsion droplets and the assembling behavior of the hydrophilic component in the Ie-BF film were studied. The confocal laser scanning microscope (CLSM) results confirm that the emulsion droplets were the main origin of pore-formation in the bulk layer. Hydrophilic components can be loaded by the reverse emulsion droplets and assembled onto the porous array of the Ie-BF structures by the one-step Ie-BF method. The Ie-BF technique provides a way of 3D pore-formation within the matrix of polymeric film. The highly dynamic control on the sublayer pore morphologies of the Ie-BF films, ranging from nano-pores to micro-porous foam-like structure, is a promising feature for constructing an efficient platform for different applications.关键词：Inverse emulsion;Breath figure;3D porous structure;Asymmetric pore morphology
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发布时间：2024-10-08 - 摘要：Highly stretchable and durable conductors are significant for the development of wearable devices, robots, human-machine interfaces, and other artificial intelligence products. However, high stretchability and small hysteresis are difficult to be attained for conventional conductive fibers, restricting their applications as stretchable electronics. In this work, a worm-inspired strain-insensitive conductive fiber with both outstanding strain-insensitive performance and small hysteresis was developed by combining surface modification, interfacial polymerization and modified pre-strain finishing to construct aqueous polyurethane@polypyrrole elastic wrinkles on an elastic multifilament. The microscopic morphology, surface composition, mechanical performance, strain-insensitive properties and durability of the composite fibers were characterized by scanning electron microscope (SEM), electronic strength tester, infrared spectroscopy (FTIR) and SourceMeter. FTIR results suggested the successful attachment of DOPA and PPy coating. Thermogravimetric analysis (TGA) demonstrated that the loading capacity of PPy exhibited an obviously increasing trend from 1.49% of PU0@PPy fiber to 6.96% of PU300@PPy fiber, and they all exhibited excellent electrical conductivity fluctuating around 100 S·m-1. More importantly, such bionic stretchable conductive fiber wrapped with elastic wrinkles not only exhibited excellent strain-insensitive behavior (ΔR/R0 = 1.88) up to 300% strain but also revealed small hysteresis (0.03) after a stretching-releasing cycle and long-term durability (>1000 stretching-releasing cycle), and it also exhibited a wonderful Q value (1.60) though it was in a state of high strain (300%) as compared to many recently reported stretchable conductors based on spirally structure, buckling structure, negative Poisson's ratio structure and so on. Accordingly, it can be applied to monitor the human body where it would undergo large deformations, such as finger joints, wrist and elbow. In addition, the resistance change of PU300@PPy fiber still kept within an order of magnitude after experiencing 200 cycles of soaping and 1000 times of strong friction. In a word, such biomimetic strain-insensitive conductive fiber holds great potential in the fields of highly stretchable electronics.关键词：Polyurethane;Polypyrrole;Worm-inspired wrinkle structure;Strain-insensitive performance
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发布时间：2024-10-08 - 摘要：A series of polyisobutylene-based thermoplastic elastomers (PIB-TPE) with different polybutyl carbamate hard segments could be synthesized via reaction of hydroxyl-terminated PIB telechelics (HO-PIB-OH) with bis(4-isocyanatocyclohexyl)methane (HMDI) and then 1,4-butanediol (BDO). The influence of HMDI/PIB molar ratio on the aggregation structure, elastic recovery, self-healing property, hydrophilcity/hydrophobicity on the elastomer surface, dynamic mechanical and tensile properties of PIB-TPE were systematically investigated. The flexible PIB segments with fully saturated structure in PIB-TPE serve as soft segments. The physically crosslinked domains ((3.6±0.5) nm) were generated due to the microphase separation between soft segments and hard segments and the crystallization from the ordered and disordered hydrogen bonds in polybutyl carbamate hard segments. The three-dimensional supramolecular network in PIB-TPE is formed at room temperature and dissociated to transform into viscous state due to melting of crystallization and dissociation of hydrogen bonds at high temperature and then gradually returned to the three-dimensional supramolecular network with decreasing temperature. The temperatures of melting of crystallization and dissociation of hydrogen bond depend on the length of hard segments in PIB-TPE. When the molar ratio of HMDI to PIB is less than 19, the temperature of melting peak of crystallization in hard segments is higher than 119 ℃. Some of the disordered hydrogen bonds in PIB-TPE could change into the ordered hydrogen bonds with storage time, leading to a great improvement in tensile strength and elongation at break of PIB-TPE materials. The PIB-TPE materials behave good elastic recovery and self-healing properties. The hydrophilcity/hydrophobicity on the PIB-TPE film surface could be adjusted by the molar ratio of HMDI to PIB or self-assembly induced by n-hexane vapor. The water contact angle (WCA) on surfaces of elastomer film decreased from 98.7° to 77.8° with an increase in the molar ratio of HMDI to PIB from 6 to 21, meaning a change from hydrophobicity to hydrophilicity. Moreover, the fully saturated PIB soft segments endow PIB-TPE elastomer with good damping performance with relatively broad damping temperature range of -55~25 ℃ and the maximum tanδ of 1.05. The above multi-block PIB-based thermoplastic elastomers would have the potential applications as biomedical, damping and self-healing functional materials.关键词：Polyisobutylene;Thermoplastic elastomer;Hydrogen bond;Supramolecular network;Melting temperature;Hydrophilcity/hydrophobicity
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发布时间：2024-10-08 - 摘要：We designed and synthesized comb-like block copolymer poly[poly(ethylene glycol) methyl ether acrylate] (PPEGA) and poly(ethylene glycol)-b-PPEGA (PEG-b-PPEGA). By mixing with the high-molecular-weight poly(L-lactic acid) (PLLA) and poly(D-lactic acid) (PDLA) blends, the effect of various PEG structures on the crystallization of PLA stereocomplex system (sc-PLA) was explored. The results measured from optical microscopy (OM) show that homopolymer PEGA and PEG and copolymer PEG-b-PPEGA are completely miscible with sc-PLA, whereas PPEGA is immiscible. The non-isothermal and isothermal crystallization data for all these blends by means of differential scanning calorimetry (DSC) indicate that both PEGA and PEG could promote the formation of stereocomplex crystallites (SCs), but reduce the crystallinity of homochiral crystallites (HCs). However, introducing PPEGA and PEG-b-PPEGA could simultaneously enhance the crystallinity of HCs and SCs. Besides, the melting points of SCs in sc-PLA/PPEGA and sc-PLA/PEG-b-PPEGA blends increase with the increasing content of these two copolymers. These might be ascribed to the local interfacial interactions between PLA and the branched-chains PEGA. From polarized optical microscopy (POM), we could find that the introduction of these four polymers could significantly increase the spherulitic growth rates but reduce the number of nuclei, indicating that the mobility of PLA chains play a key role on the increased crystallinity of SCs. X-ray analysis further revealed that miscible PEGA could induce higher long spacing of SCs in sc-PLA/PEGA blends than that in sc-PLA/PPEGA blends and comb-like PPEGA has a significant impact on the thickening of SCs, resulting in a higher melting point of SCs. In addition, although the block copolymer PEG-b-PPEGA formed by PEG and PPEGA promotes the miscibility of PPEGA with PLA, PPEGA would adversely affect the interaction between PEG and PLA molecular chains during crystallization, and thus the synergistic effect of PEG and PPEGA on promoting crystallization is weakened.关键词：Poly(ethylene glycol);Poly(lactic acid);Stereocomplex;Crystallization
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发布时间：2024-10-08 - 摘要：Reactive compatibilization is an efficient way to enhance the interfacial adhesion and improve the toughness of the blends. In this study, a fully bio-based aliphatic polyester (PBSePM) containing malic acid moiety was synthesized. Then, super-tough poly(lactic acid) (PLA)/malic acid-based aliphatic polyester blends (PLA/PBSePM) were prepared by reactive blending in the presence of hexamethylene diisocyanate (HDI). The reactive blending behavior was investigated by torque, proton nuclear magnetic resonance (1H-NMR), Fourier transform infrared spectroscopy (FTIR), and wide-angle X-ray diffraction (WAXD). The effects of HDI addition on the tensile properties, rheological behavior, phase morphology, and melting and crystallization behavior of PLA/PBSePM blends were studied by dynamic rheometer, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). The results showed that the gel fraction and complex viscosity of the blends increased with the increase of the amount of HDI. In the reactive blending processing, HDI reacted with PBSePM and PLA. The in situ PLA-PBSePM copolymer was formed, which acted as a compatibilizer to enhance the interfacial adhesion between PLA and PBSePM. With the increase of HDI, the phase interface of the blends became blurred, and the compatibility was significantly improved. The cavities emerged in the tensile fracture surfaces and impact fracture surfaces of the reactive blends, which would dissipate energy during the stretching and impacting evolution. With the increase of HDI content, the interfacial adhesion was too strong, which delays the occurrence of matrix yielding; hence, the toughness decreased. All the blends presented a great tensile toughness with an elongation at break higher than 300%. The impact toughness of the blends significantly increased first and then slightly decreased with the increasing amount of HDI. The notched impact strengths of all the reactive blends are higher than 53 kJ/m2, indicating a super-tough behavior. The highest notched impact strength of 81.5 kJ/m2 was achieved while adding 2.9 wt% HDI. With the increase of HDI, the crystallization capacity of PLA decreased, the glass transition temperature and cold crystallization temperature increased first and then almost remained unchanged; meanwhile, the melting enthalpy decreased. This study suggested that incorporated malic acid into aliphatic polyester and then reactive blending would be an efficient way to obtain bio-based super-tough PLA materials.关键词：Poly(lactic acid);Copolyester;Malic acid;Reactive blending;Super-tough
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发布时间：2024-10-08
Research Article
- 摘要：Laser light scattering (LLS), which includes static light scattering (SLS) and dynamic light scattering (DLS), has been widely applied in characterization of polymer samples in dilute solutions. SLS measures the angular dependence of the excess scattered intensity, from which the weight average molecular weight, radius of gyration, and second viral coefficient are obtained. DLS measures the intensity-intensity time correlation functions, from which the hydrodynamic radius and size distribution are obtained. The combination of SLS and DLS enables information on chain conformation. Beside synthetic polymers, LLS is also suitable for the solutions and suspensions of biopolymers, microbial, colloids, nanoparticles, virus, and vesicles. The history, theory, and experimental techniques of SLS and DLS specific for dilute solutions are summarized. In recent years, the cross-correlation techniques, diffusing wave spectroscopy, and other related techniques have been developed to expand LLS to study samples in semi-dilute and even concentrated solutions. These techniques, as well as solid light scattering, are also briefly introduced in this review. In the last, we provide four typical examples of light scattering experiments: the coil-to-globule transition as studied by the combination of SLS and DLS, the scaling of hyperbranched polymers as determined by LLS, the polymerization-induced micellization process as monitored by time-resolved LLS, and the aggregation of nanoparticles in biological media as investigated by depolarized DLS.关键词：Laser light scattering;Polymer characterization;Molecular weight;Radius of gyration;Correlation function
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发布时间：2024-10-08
Review (Special Topic: Techniques of Polymer Characterization)
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