Monthly ,Founded in 1964 Resume Publication in 1980 Editor-in-Chief:YU Jihong ISSN 0251-0790 CN 22-1131/O6
Shear banding in polymer fluids represents a paradigmatic example of strain localization under strong nonlinear shear flow, with its physical origin and regulatory mechanisms standing as central scientific questions in polymer rheology. Large-scale molecular dynamics simulations have firmly established shear banding as an intrinsic bulk phenomenon under specific shear conditions, often accompanied by a stress plateau in the steady-state shear stress-shear rate curve. Emerging studies reveal that the spatial localization of shear bands is determined by the initial structural heterogeneity of the entanglement network, where pre-existing "weak spots" in the equilibrium state, such as regions with sparse multiple entanglements, act as nucleation sites for shear stain concentration. Investigations on bidisperse systems further demonstrate that chain-length-dependent migration and selective enrichment drive a "fast-band softening-slow-band hardening" coupling mechanism, which is critical for the long-term stability of shear bands. This review synthesizes recent advances in understanding shear banding, focusing on its intrinsic nature, formation mechanisms, dynamic evolution, and stability, and summarizes the key controversies, challenges, and future research directions in shear band studies. It emphasizes that achieving effective prediction and regulation of shear bands, through the development of high spatiotemporal resolution in-situ characterization techniques and the advancement of multi-scale simulations and theories, will provide critical theoretical support for guiding the precision forming of polymeric materials. This includes controlling rheological uniformity in processes such as injection molding and extrusion, as well as enabling the controlled fabrication of advanced products like ultra-thin films and ultra-fine fibers, thereby significantly enhancing processing efficiency and product performance.
Holographic optical storage exhibits recording and reconstructing ability for three-dimensional information based on optical interference and diffraction. It has ultra-high storage density and parallel reading and writing ability, and becomes an important developing direction of information storage. Among various kinds of holographic storage media, azo molecules have attracted much attention due to their advantages such as small molecular size, polarization sensitivity, fast light response, large refractive index changes, and high compatibility with polymer matrix. Herein, we review the applications of azo materials in polarization holographic storage and surface relief gratings in the past 40 years, especially the design and experimental results of high-density multiplexing polarization holographic storage in azo molecule-doped polymer thin films. The feasibility of application of azo-based thin films in photon integrated chip is also analyzed.
Among various architectures of polymers, end-group-free rings have attracted growing interests due to their distinct physicochemical performances over the linear counterparts which are exemplified by reduced hydrodynamic size and slower degradation. It is key to develop facile methods to large-scale synthesis of polymer rings with tunable compositions and microstructures. Recent progresses in large-scale synthesis of polymer rings against single-chain dynamic nanoparticles, and the example applications in synchronous enhancing toughness and strength of polymer nanocomposites are summarized. Once there is the breakthrough in rational design and effective large-scale synthesis of polymer rings and their functional derivatives, a family of cyclic functional hybrids would be available, thus providing a new paradigm in developing polymer science and engineering.
Compared with one-dimensional(1D) and three-dimensional(3D) polymers, the theory framework of two-dimensional(2D) polymers is still incomplete, especially for flexible 2D polymers. Their unique conformation and properties are one of the mysterious questions in the polymer science. This article comprehensively reviews the theoretical and simulation research progress of flexible 2D polymers, aiming to systematically sort out the development of the field of flexible 2D polymers from early theoretical prototypes to recent conformational physics research. First, this article reviews theoretical research on tethered membranes from the 1980s. Early molecular dynamics simulations revealed that self-avoidance causes 2D networks to approach a flat state at the thermodynamic limit, rather than undergoing a crumpled transition. Building on this foundation, this article further elaborates on significant breakthroughs in the field since the 21st century. Computer simulations have not only validated the scaling relationships between the equilibrium conformations of 2D polymers and their transport properties(such as intrinsic viscosity), but also theoretically unified the long-debated flat and crumpled conformations by introducing an adjustable mesh model, thereby revealing the physical mechanism of their coexistence. Furthermore, a complete conformational evolution path-ranging from flat to multi-level folded, and ultimately to collapsed states has been systematically established. Finally, this article provides an outlook on the opportunities and challenges facing the field, particularly regarding the precise preparation of ordered flexible networks and the utilization of theoretical insights to guide the design of intelligent responsive materials.
As a key representative of high-performance polymers, polyimide plays an irreplaceable role in strategic emerging fields such as integrated circuits, new energy, and aerospace, owing to its exceptional thermal resistance, outstanding mechanical properties, and remarkable dielectric characteristics. However, with the rapid development of cutting-edge areas such as flexible electronics, efficient energy conversion, and the “dual-carbon” strategy, traditional polyimide materials still face significant challenges in terms of dielectric properties, flexibility, functional integration, and thermal management. In response, this paper systematically reviews the innovative research achievements in multifunctional polyimides, focusing on five key dimensions: “IC, display, device/gas separation, composite.” Specifically, at the “IC” level, material systems with ultra-low dielectric constants and high strength have been developed for advanced chip packaging. At the “dsiplay” level, highly transparent and flexible films with excellent folding endurance have been fabricated to meet the demands of flexible displays. In the “device/gas separation” dimension, applications in energy devices and aerospace thermal management have been expanded, while structural designs have significantly enhanced gas separation performance, contributing to the “dual-carbon” goals. At the “composite” level, breakthroughs in thermal management capabilities of composites have been achieved by constructing multi-dimensional thermal conduction networks. This study not only demonstrates the considerable functional plasticity of polyimides but also provides important theoretical and technical support for addressing key material challenges in related scientific and technological fields.
Electrochemical water splitting represents a sustainable technology for hydrogen(H2) production. However, its large-scale implementation is hindered by the high overpotentials required for both the cathodic hydrogen evolution reaction(HER) and the anodic oxygen evolution reaction(OER). Transition metal-based catalysts have garnered significant research interest as promising alternatives to noble-metal catalysts, owing to their low cost, tunable composition, and noble-metal-like catalytic activity. Nevertheless, systematic reviews on their application as bifunctional catalysts for overall water splitting(OWS) are still limited. This review comprehensively outlines the principal categories of bifunctional transition metal electrocatalysts derived from electrospun nanofibers (NFs), including metals, oxides, phosphides, sulfides, and carbides. Key strategies for enhancing their catalytic performance are systematically summarized, such as heterointerface engineering, heteroatom doping, metal-nonmetal-metal bridging architectures, and single-atom site design. Finally, current challenges and future research directions are discussed, aiming to provide insightful perspectives for the rational design of high-performance electrocatalysts for OWS.
Proton exchange membrane fuel cell(PEMFC) has outstanding advantages such as high energy conversion efficiency, fast start-up speed, easy operation and maintenance. In the temperature range of 120 to 250 ℃, the operation of high-temperature proton exchange membrane fuel cells(HT-PEMFC) does not rely on the presence of water for proton conduction. This can effectively simplify the water management system, enhance the kinetics of electrode reactions, and strengthen the anti-poisoning ability of platinum-based electrocatalysts. At present, phosphoric acid(PA)-doped polybenzimidazole(PBI) membrane is the preferred membrane material in HT-PEMFC, but it faces key challenges, such as poor antioxidant stability and PA loss. In this review, the transport mechanism of PA-doped high-temperature proton exchange membranes(HT-PEM) is first clarified, and such materials are systematically classified based on the research progress in the past 10 years. Finally, the key technical challenges and coping strategies of HT-PEM are analyzed, and the future development trend is prospected.
A shear-heating method was employed to induce the formation of silk fibroin hydrogels enrich in β-sheet structures. The effects of shear duration, incubation temperature, and protein concentration on the kinetics of β-sheet assembly and the mechanical properties of resulting hydrogels were systematically investigated. The results demonstrated that a 0.03 g/mLsilk fibroin solution subjected to shear at 10000 r/min for 10 min and followed by incubation at 60 ℃ completed gelation within 30 min, yielding a physically cross-linked network containing 63.51% β-sheet structures, with a storage modulus of 25.70 kPa and a compressive strength of 108.29 kPa. Furthermore, the self-assembly kinetics of molecular chain transition from random coils to β-sheet structures and the corresponding evolution of mechanical properties were elucidated. This work provides optimized processing strategies and experimental evidence for the preparation of shear-induced silk fibroin hydrogels and supports their potential applications in tissue engineering.
Cyclopentadithiophene(CPDT)-based polymers have emerged as promising research platforms for multicolor electrochromic materials due to their favorable color tunability. However, insufficient cyclic stability has hindered their translation into practical applications. In this study, two CPDT-based conjugated polymers with distinct substituent groups were designed and synthesized: PCPDT-Ph(copolymerized with unsubstituted benzene units) and PCPDT-PhOMe(copolymerized with dimethoxy-substituted benzene units). The influence of dimethoxy substitution on the electrochromic properties and stability of the polymers was systematically investigated. Electrochemical and electrochromic characterizations demonstrated that the electron-donating ability of the dimethoxy groups not only effectively regulated the polymer’s intrinsic properties but also significantly enhanced its cycling stability. Compared with PCPDT-Ph, PCPDT-PhOMe exhibited a reduced onset oxidation potential from 0.66 V(vs. Ag/AgCl) to 0.46 V, an upshifted highest occupied molecular orbital(HOMO) energy level, and a narrowed optical band gap(calculated theoretically) from 1.73 eV to 1.61 eV. The PCPDT-PhOMe film showed magenta in the neutral state and transparency in the oxidized state, with a color difference(ΔEab*) of 46.36. The coloring/bleaching response times were measured as 0.7/0.6 s, and the optical contrast retention reached 84% after 1000 cycles, outperforming the PCPDT-Ph film(79.5% retention after 500 cycles). Additionally, it exhibited a coloration efficiency of 543.9 cm²/C, demonstrating favorable comprehensive electrochromic performance. Electrochromic devices assembled with PCPDT-PhOMe achieved reversible switching between magenta and transparent states, with a response time of ≤1.0 s and a contrast retention of 71% after 30000 cycles, indicating good stability. This work clarifies the role of substituent electronic effects in regulating the electrochromic properties of CPDT-based polymers, providing experimental basis and theoretical support for the molecular design of solution-processable thiophene-based electrochromic materials. Furthermore, it validates the potential application of PCPDT-PhOMe in smart windows, electronic displays, and other related fields.
Through dip-coating technology, a series of composite coatings was fabricated by adjusting the concentration parameters of nano-SiO2 particles, PMMA, and dichloromethane(CH2Cl2) solvent. Systematic characterization using the contact angle measurements and the UV-Vis spectrophotometry revealed that the material achieved optimal performance balance of superhydrophobicity and transparency at a nanoparticle concentration of 6.25 g/L, exhibiting a static contact angle of (160.8±1.1)° and a transparency exceeding 90% at 550 nm. Mechanistic analysis revealed that the hierarchical micro-nano structures formed by nanoparticles at this concentration synergistically interacted with the polymer matrix, concurrently generating the surface roughness for the superhydrophobic Cassie-Baxter state while preventing Mie scattering effects to preserve the high transparency typically compromised by excessive particles. This research highlights advantages such as the availability of raw materials, straightforward processing, and low manufacturing costs, demonstrating promising self-cleaning potential and broad application prospects in the protection of optical device surfaces and the self-cleaning of photovoltaic modules.
In this work, we proposed a strategy for the hydrolysis of native corn starch after the treatment of corn starch in an ionic liquid aqueous solution, and it is an awfully “green” and simple means to obtain starch with low molecular weight and amorphous state. X-ray diffraction results revealed that the natural starch crystalline region was largely disrupted by ionic liquid owing to the broken intermolecular and intramolecular hydrogen bonds. After hydrolysis, the morphology of starch changed from particles of native corn starch into little pieces, and their molecular weight could be effectively regulated during the hydrolysis process, and also the hydrolyzed starch samples exhibited decreased thermal stability with the extension of hydrolysis time. This work would counsel as a powerful tool for the development of native starch in realistic applications.
Carbonized polymer dots(CPDs), as an important branch of carbon dots, have demonstrated remarkable performance and processing and molding advantages in the field of solid-state luminescent materials due to their unique sub-fluorescent groups and polymer-like structures. Specifically, the sub-fluorescent groups in the shell of CPDs avoid the generation of π-π interactions due to the presence of polymer components, thereby effectively suppressing the quenching caused by aggregation. Therefore, CPDs are ideal and highly efficient solid-state luminescent materials with development potential. To achieve efficient solid-state luminescence of CPDs, a series of CPDs was prepared using linear polyacrylic acid and organic small molecules of different functionalities as co-precursors through a hydrothermal process. The polymer molecular chain on the outer layer of CPDs isolates and disperses the fluorescence center, effectively suppressing the aggregation-caused quenching effect and ensuring the solid-state luminescence performance. Based on the crosslink-enhanced emission effect, the influence of the average functionality of co-precursors on the luminescence performance of CPDs was systematically studied. The results show that with the increase of the functionality and crosslinking degree of the precursors, the fluorescence quantum yield and
room-temperature phosphorescence lifetime of CPDs are significantly enhanced, effectively improving the solid-state luminescence performance.
In this study, a novel polysaccharide GPA-G2-H was derived from ginseng. Furthermore, the coherent study of its structural characteristics, fermented characteristics in vitro, as well as antioxidant mechanism of fermented product FGPA-G2-H on Aβ25-35-induced PC12 cells were explored. The structure of GPA-G2-H was determined by means of zeta potential analysis, FTIR, HPLC, XRD, GC-MS and NMR. The backbone of GPA-G2-H was mainly composed of →4)-α-D-Glcp-(1→ with branches substituted at O-3. Notably, GPA-G2-H was degraded by intestinal microbiota in vitro with total sugar content and pH value decreasing, and short-chain fatty acids(SCFAs) increasing. Moreover, GPA-G2-H significantly promoted the proliferation of Lactobacillus, Muribaculaceae and Weissella, thereby making positive alterations in intestinal microbiota composition. Additionally, FGPA-G2-H activated the Nrf2/HO-1 signaling pathway, enhanced HO-1, NQO1, SOD and GSH-Px, while inhabited Keap1, MDA and LDH, which alleviated Aβ-induced oxidative stress in PC12 cells. These provide a solid theoretical basis for the further development of ginseng polysaccharides as functional food and antioxidant drugs.
This study employed cross-linking units with star-like topology of varying sizes ethoxylated trimethylolpropane triacrylate(ETPTA), polyhedral oligomeric silsesquioxanes(POSS) and nano-zirconia) as cross-linking cores to chemically cross-link with poly(ethylene glycol) diacrylate(PEGDA), constructing three polymer networks(EP, PP and ZP) for application in quasi-solid-state dye-sensitized solar cells(DSSCs). The results demonstrate that the strategy of increasing the size of the cross-linking core effectively enlarges the free volume of the polymer, reduces its glass transition temperature, and consequently enhances its low-temperature electrochemical performance. At a low temperature of -40 ℃, the power conversion efficiency(PCE) of the ZP-based device shows a significant increase of 37.4% compared to the EP-based device. This research provides a novel and effective strategy for developing quasi-solid-state electrochemical devices suitable for high altitude environment.
Monitoring biogenic amines, which are metabolic byproducts of shrimp spoilage, is crucial for assessing food quality. Currently, most detection methods for biogenic amines suffer from limitations such as time-consuming procedures, complex operations, and delayed results. Colorimetric analysis techniques have gained attention in recent years due to their advantages of short analysis time, simple operation, and suitability for on-site testing. This study successfully developed a series of colorimetric sensor platforms for biogenic amines by loading the natural active ingredient curcumin(CUR) and its derivative of Boron complex BFCUR onto filter paper and electrospun nanofibre films(ENFs), respectively. By analyzing the color response differences of these sensors upon contact with biogenic amines, the colorimetric sensors with superior detection performance were selected and further applied to the visual monitoring and indication of shrimp spoilage processes.
This study addressed the critical challenge of the limited dissolved oxygen in traditional photoelectrochemical enzyme biosensors by proposing a construction strategy for a “solid-liquid-gas three-phase enzymatic reaction interface”, utilizing a three-dimensional(3D) dendritic nanostructure. The methodology involved the preparation of titanium dioxide(TiO2) nanowire arrays featuring a 3D dendritic structure on fluorine-doped tin oxide conductive glass through a two-step hydrothermal process. Following selective hydrophobic and hydrophilic treatments, along with enzyme modification, a stable three-phase interface was successfully established. This innovative design facilitates the direct transport of oxygen to the catalytic sites via the gas phase, effectively addressing the limitations associated with insufficient oxygen supply at the conventional solid-liquid two-phase interface. Experimental results demonstrate that the linear detection range of this sensor has been enhanced by a factor of 20 compared to traditional structures, while exhibiting excellent stability(relative standard deviation<2%). This research introduces a novel construction strategy for the development of highly sensitive and stable photoelectrochemical sensors, which may significantly contribute to the early diagnosis of chronic diseases.
In this work, choline was employed as both a catalyst and a reducing agent to catalyze the hydrolysis/ condensation of tetraethyl orthosilicate and reduce chloroauric acid tetrahydrate. Through a one-step concerted reaction process, successfully prepared Au/mesoporous silica composite particles. Transmission electron microscopy(TEM) and nitrogen desorption characterization revealed that thickness of the mesoporous shell increased from 30 nm to 20 and 8 nm when the pre-treatment time after the addition of choline was delayed from 4 min to 8 and 15 min, respectively. Additionally, when the concentration of cetyltrimethylammonium bromide in the reaction medium increased from 2.0 mmol/L to 8.0 mmol/L, mesoporous pore diameter of the silica shell increased from 2.0 nm to 2.8 nm. Finally, as the volume ratio of water to ethanol decreased from 15∶1 to 13∶3, number of the Au particles encapsulated within the mesoporous silica shells could be further adjusted, transitioning from single-core to multi-core encapsulation, and the catalytic results showed that the multi-core encapsulated Au/mesoporous silica composite particles exhibited higher catalytic activity.
Using indole squaraine cyanine as the fluorescent scaffold, we successfully designed and synthesized a wash-free fluorescent probe, designated as CSE, through the introduction of cationic salts. Performance characterization demonstrated that CSE not only exhibits excellent photostability but also possesses near⁃infrared fluorescent emission. Intracellular co⁃localization assays with commercial mitochondria⁃specific dyes further validated its ability to precisely target mitochondria. Under stimulated emission depletion(STED) super⁃r esolution microscopy with depletion of 775 nm, CSE clearly resolved the fine morphological details of mitochondrial cristae, achieving an impressive spatial resolution of up to 54 nm. During super⁃resolution dynamic tracking of mitochondria leveraging CSE, we successfully captured and delineated key dynamic events, including mitochondrial fusion and fission, cristae remodeling, and tubulation of mitochondria. The CSE probe developed herein enables super⁃resolution imaging and dynamic tracking of mitochondrial cristae, thereby holding great promise as a powerful tool for dissecting the dynamic mechanisms of mitochondrial cristae under physiological conditions.
Polydiphenylacetylenes(PDPAs) modified with D-/L-phenylglycine side chains have been prepared by post-polymerization modification strategy and their structures were well characterized using multiple spectroscopic technologies. Taking the advantage of the activated ester strategy, the species and content of the D-/L-phenylglycines in the polymers can be well-controlled. The chirality of these phenylglycine-modified PDPAs exhibits unique composition and solvent-dependent behaviors. No circular dichroism(CD) signals have been recorded for the homo-polymers P-L and P-D(with complete substitution by L- and D-phenylglycine) in different solvents. While some of the partially phenylglycine-substituted PDPAs exhibit induced CD signals, for example, P-L(1∶19)(the digitals in the brackets stand for the ratio of the L- or D-phenylglycine to activated ester groups) in tetrahydrofuran(THF) and dichloromethane(DCM), P-D(1∶19) and P-D(1∶39) in the mixtures of THF and dimethyl sulfone(DMSO). In addition to their chiral characteristics, these PDPAs show typical aggregation-enhanced emission(AEE) behavior. Over 220% enhancement in fluorescence intensity has been recorded for P-L(1∶19) in THF/DMSO mixture solvent. Both of the substitution-/solvent-dependent chirality transmission and AEE behaviors can be associated with the strong interactions between the phenylglycine side chains, which are non-facile to the conformational change of the polydiphenylacetylene backbone and hinder the chirality transmission from side to main chains. Meanwhile, the strong interactions reduce the dissipation of the excited state energy by intramolecular motions and induce the fluorescence enhancement. These observations are not only experimentally consistent, but also theoretically compliant with the results of density function theory(DFT) and molecular dynamics(MD) simulations.
High-performance polydicyclopentadiene(PDCPD) elastomeric materials were prepared by copolymeri-zing dicyclopentadiene(DCPD) with tricyclopentadiene(TCPD) and introducing a low-molecular-weight polybuta- diene(PB) with good compatibility for blending modification. The copolymerization of DCPD and TCPD allowed for the tuning of material rigidity; the introduction of PB decreased the crosslinking density, reduced the proportion of rigid cyclic structures, and provided a plasticizing effect, collectively transforming PDCPD from a rigid thermoset into a flexible elastomer. When the PB content(mass ratio to DCPD/TCPD mixture) reached 35%, the modified PDCPD exhibited a tensile strength of 12 MPa and an elongation at break of 296%, demonstrating a thermoset elastomeric behavior. Scanning electron microscopy of the tensile fracture surface, dynamic mechanical analysis, and thermogravimetric analysis indicated that PB existed in the system as a physically blended phase. Although excessive PB addition slightly deteriorated the water resistance, the maximum water absorption of the material remained below 0.9% after immersion in deionized water at 60 ℃ for 48 h. This study provided an effective approach to transforming PDCPD into an elastomer through blending modification with low-molecular-weight polymers.
To address the issues of polyaniline(PANI) aggregation and thermal degradation in conventional melt-blended polyetheretherketone(PEEK)/PANI composites, we developed a one-step in-situ synthesis method starting from copolymer precursor films. A series of precursor films based on PAEN copolymer was prepared by varying the molar ratio of the key monomers, N-phenyl(4,4′-difluorodiphenyl) ketone-amine(PDK) and 4,4′-difluorodiphenyl ketone. These precursors were subsequently converted into PEEK/PANI composite films through side-chain hydrolysis and oxidative coupling. The results showed that the composite film with a 9/1 monomer ratio(denoted as PEEK/PANI-0.9) exhibited the best overall performance. Scanning electron microscopy(SEM) characterization revealed a dense and uniform surface morphology without obvious pores. Electrically, a 40 μm-thick PEEK/PANI-0.9 film achieved a conductivity of 4.78×10-⁴ S/m. In summary, this method successfully produces PEEK films with well-dispersed, high content PANI, showing promise for applications in areas requiring conductivity, antistatic protection, electromagnetic shielding and wave absorption.
In this study, polyacrylic acid(PAA) films were employed as a model system, and a series of PAA films with tunable water wettability was systematically prepared by varying molecular weight and curing temperature. Using attenuated total reflectance Fourier-transform infrared spectroscopy(ATR-FTIR), the molecular configurations of surface carboxyl groups(COOH), free carboxyl(COOHf) and hydrogen-bonded carboxyl(COOHHB), were directly correlated with the polar component of surface energy(γs,p). By decomposing the γs,p values of the PAA thin films as a sum of the contributions of COOHf and COOHHB, the intrinsic polar component of surface energy of COOHHB(γHBs,p*) was quantified for the first time as 8.34 mN/m, significantly lower than that of COOHf(γfs,p*=34 mN/m). This result highlights that hydrogen bonding markedly reduces the γs,p, providing a rational explanation for the relatively large water contact angle observed on PAA thin films. Furthermore, it establishes a thermodynamic basis for estimating the fraction of surface COOHHB groups(fHB) from wettability measurements. Further extension of the model to carboxyl- terminated self-assembled monolayers(COOH-SAMs) revealed that surface COOH density(∑COOH) critically regulates wetting behavior: when ∑C OOH ranges from 4.30 to 5.25 nm-², COOH groups predominantly exist in a free state and facilitate effective hydration layers, thereby promoting superhydrophilicity. Overall, this study not only establishes a unified thermodynamic framework linking surface COOH configurations to macroscopic wettability, but also validates its universality by extending it to COOH-SAMs systems, thereby providing a unified theoretical framework for the controllable design of hydrophilicity in various COOH-functionalized surfaces.