With the quick emergence of antibiotic resistance and multi-drug resistant microbes, more and more attention has been paid to the development of new antimicrobial agents that have potential to take the challenge. Polysaccharides, as one of the major classes of biopolymers, were explored for their antimicrobial properties and applications, owing to their easy accessibility, biocompatibility and easy modification. Polysaccharides and their derivatives have variable demonstrations and applications as antimicrobial agents and antimicrobial biomaterials. A variety of polysaccharides, such as chitosan, dextran, hyaluronic acid, cellulose, other plant/animal-derived polysaccharides and their derivatives have been explored for antimicrobial applications. We expect that this review can summarize the important progress of this field and inspire new concepts, which will contribute to the development of novel antimicrobial agents in combating antibiotic resistance and drug-resistant antimicrobial infections.

Direct arylation methods have been used to polymerize thienylmethylene oxindoles (TEIs) and 3,3-bis[[(2-ethylhexyl)oxy]methyl]-3,4-dihydro-2H-thieno-[3,4-b][1,4]dioxepin (ProDOT) for new donor-acceptor conjugated polymers. The polymers exhibited blue hues in neutral-state with distinct color-to-transmissive reversible electrochromic switching under applied potentials from 0 V to +1.5 V, and showed high coloration efficiencies (436−438 cm²·C⁻¹) in near-infrared regions with high switching speeds around 1−2 s under ambient conditions.

Stimulus-responsive polymers containing dynamic bonds enable fascinating properties of self-healing, recycling and reprocessing due to enhanced relaxation of polymer chain/network with labile linkages. Here, we study the structure and properties of a new type of thermoplastic polyurethanes (TPUs) with trapped dynamic covalent bonds in the hard-phase domain and report the frustrated relaxation of TPUs containing weak dynamic bond and π-π interaction in hard segments. As detected by rheometry, the aromatic TPUs with alkyl disulfide in the hard segments possess the maximum network relaxation time in contrast to those without dynamic bonds and alicyclic TPUs. In situ FTIR and small-angle scattering results reveal that the alkyl disulfide facilitates stronger intermolecular interaction and more stable micro-phase morphology in π-π interaction based aromatic TPUs. Molecular dynamics simulation for pure hard segments of model molecules verify that the presence of disulfide bonds leads to stronger π-π stacking of aromatic rings due to both enhanced assembling thermodynamics and kinetics. The enhanced π-π packing and micro-phase structure in TPUs further kinetically immobilize the dynamic bond. This kinetically interlocking between the weak dynamic bonds and strong molecular interaction in hard segments leads to much slower network relaxation of TPU. This work provides a new insight in tuning the network relaxation and heat resistance as well as molecular self-assembly in stimulus-responsive dynamic polymers by both molecular design and micro-phase control toward the functional applications of advanced materials.

Flexible and wearable strain sensors for human-computer interaction, health monitoring, and soft robotics have drawn widespread attention to promising applications in the next generation of artificial intelligence devices. However, conventional semiconductor sensors are difficult to meet the requirements of flexibility and stretchability. Here, we reported a kind of novel and simple sensor based on layer-by-layer (LBL) method. Carbon nanotubes (CNTs) layer provides high ductility and stability in the process of tension sensing, while silver layer provides low initial resistance and fast reflecting in the process of tension sensing. LBL method ensures the uniformity of the conductive layer. The sensor has superior sheet resistance of 9.44 Ω/sq., high elongation at break of 104%. For sensing capability, the sensor has wide reflecting range of 60%, high gauge factor (GF) of 1000 up to 60% strain, fast reflecting time of 165 ms. Excellent reliability and stability have also been verified. It is also worth mentioning that the entire process does not require any expensive equipments, complicated processes or harsh experimental conditions. The above features provide an idea for large-scale application of flexible stretchable sensors.

High-performance carbon nanofibers are highly dependent on the performance of their precursors, especially polyacrylonitrile (PAN). In this work, the copolymer of PAN (coPAN) was synthesized for electrospinning. A self-assembling set-up was used for the stretching of single coPAN nanofibers. FTIR and Raman spectroscopies were used to characterize the chemical structure of coPAN nanofibers. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to monitor the morphology of single coPAN nanofibers under different drawing times. Micro-tensile test was used to determine the mechanical properties of single coPAN nanofibers. The results indicated that the drawing led to an increase in degree of molecular orientation along the fiber axis from 0.656 to 0.808, tensile strength from 304 MPa to 595 MPa, and modulus from 3.1 GPa to 12.4 GPa. This research would provide fundamental information of high-performance electrospun coPAN nanofibers and offer opportunities for the preparation of high-performance carbon nanofibers.

Due to the important role of oil source in our life, the separation of water-in-oil emulsion is urgent and necessary. Membrane seperation technology has been an efficient and widely used method in separating oil-water separation. Herein, we report a versatile approach to fabricate surface carbonized membranes with self-standing property from biomass-derived precursor by synergistic charring of phytic acid, arginine and filter paper. The obtained membrane exhibited superhydrophobicity in oil, excellent fouling resistance, and self-supporting ability. The membrane can be cycle-used at least 12 times with high permeation flux (up to 1380 L·m⁻²·h⁻¹) and separation efficiency (up to 99.4%).

In this work, ultra-high molecular weight polyethylene (UHMWPE) microfiltration hollow fiber membranes prepared via the thermally induced phase separation (TIPS) method were modified by chemically bounding hydrophilic silica (SiO₂) nanoparticles onto the surface to improve anti-fouling performance. A range of testing techniques including attenuated total reflection Flourier transformed infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), water contact angle, mechanical test, filtration and anti-fouling performance were carried out to discuss the influence of different modification conditions on the properties of the membranes. The prepared hollow fiber membranes display the significantly excellent performance when the vinyl trimethoxy silane (VTMS) concentration was 13%, the pH value of the hydrolyzate was 4 and the hydrolysis reaction time was 6 h. In particular, the hydrophilicity of modified membranes was improved effectively, resulting in the enhancement of membrane anti-fouling properties. The results of this work can be consulted for improving the anti-fouling performance of the UHMWPE microfiltration hollow fiber membrane applied in the field of water purification.

Elastomeric vitrimers with covalent adaptable networks are promising candidates to overcome the intrinsic drawbacks of conventional covalently-crosslinked elastomers; however, most elastomeric vitrimers show poor mechanical properties and require the addition of exogenous catalysts. Herein, we fabricate a catalyst-free and mechanically robust elastomeric vitrimer by constructing a segregated structure of sodium alginate (SA) in the continuous matrix of epoxidized natural rubber (ENR), and further crosslinking the composite by exchangeable hydroxyl ester bonds at the ENR-SA interfaces. The manufacturing process of the elastomeric vitrimer is facile and environmentally friendly without hazardous solvents or exogenous catalysts, as the abundant hydroxyl groups of the segregated SA phase can act as catalyst to activate the crosslinking reaction and promote the dynamic transesterification reaction. Interestingly, the segregated SA structure bears most of the load owing to its high modulus and small deformability, and thus ruptures preferentially upon deformation, leading to efficient energy dissipation. Moreover, the periodic stiffness fluctuation between rigid segregated SA phase and soft ENR matrix is beneficial to the crack-resisting. As a result, the elastomeric vitrimer manifests exceptional combination of catalyst-free, defect-tolerance, high tensile strength and toughness. In addition, the elastomeric vitrimer also exhibits multi-shape memory behavior which may further broaden its applications.

With the expanding application of capacitors, thermal resistant dielectric materials are in high demand due to the increasing harsh environments where the capacitors are needed and the heat generated by the capacitors. Herein, we present polyarylene ether nitrile and titanium dioxide hybrids which can be used as thermal resistant dielectrics for these capacitors. Phthalonitrile modified titanium dioxide (TiO₂-CN) and phthalonitrile end-capped polyarylene ether nitrile (PEN-Ph) are firstly prepared. After being cast into TiO₂-CN/PEN nanocomposite films, these composites self-crosslink upon heating at 320 °C for 4 h, forming the polyarylene ether nitrile and titanium dioxide hybrids (TiO₂-PEN). Improved dielectric constants which are stable from room temperature to 200 °C of these hybrids are observed, indicating the potential application of the hybrids as thermal resistant dielectrics.

Thermal properties such as melting temperature can well reflect the microstructure of the polymer material, and have practical implications in the application of nanofibers. In this work, we investigated the melting temperature of individual electrospun poly(vinylidene fluoride) (PVDF) nanofibers with diameters ranging from smaller than 200 nm to greater than 2 μm by the local thermal analysis technique. The PVDF fibers obtained under four different conditions were found to crystallize into α and β phases, and the fiber mats showed typical values in the crystallinity and T_m with no significant difference among the four. However, analyses at single fiber level revealed broad distribution in diameter and T_m for the fibers produced under identical electrospinning condition. The T_m of individual nanofibers was found to remain constant at large diameters and increase quickly when reducing the fiber diameter toward the nanoscale, and T_m values of 220−230 °C were observed for the thinnest nanofibers, much higher than the typical values reported for bulk PVDF. The T_m and molecular orientation at different positions along a beaded fiber were analyzed, showing a similar distribution pattern with a minimum at the bead center and higher values when moving toward both directions. The results indicate that molecular orientation is the driving mechanism for the observed correlation between the T_m and the diameter of the nanofibers.

Developing an effective method for improving the reproducibility of positive temperature coefficient (PTC) effect is of great significance for large-scale application of polymer based PTC composites, owing to its contribution to the security and reliability. Herein, we developed a carbon black (CB)/high density polyethylene (HDPE)/poly(vinylidene fluoride) (PVDF) composite with outstanding PTC reproducibility, by incorporating 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([OMIm][NTf₂]) into the composite. After multiple repeated temperature cycles, the PTC performance of as-prepared material keeps almost unchanged and the varition of resistance at room temperature is less than 7%. Our studies revealed that [OMIm][NTf₂] contributes to the improvement of PTC reproducibility in two ways: (i) it acts as an efficient plasticizer for refining the co-continuous phase morphology of HDPE/PVDE blends; (ii) it inhibits the crystallization of PVDF through the dilution effect, leading to more overlaps of the volume shrinkage process of HDPE and PVDF melt which results in the decrease of interface gap between HDPE and PVDF. This study demonstrated that ionic liquids as the multifunctional agents have great potential for improving the reproducibility in the application of the binary polymer based PTC composites.

New ambient sound absorption material, lightweight isocyanate-based polyimide foam (IBPIF), was fabricated by operable combination between different distinctive acoustic IBPIF. Cellular structure of IBPIF was facilely and obviously adjusted by increased slurry temperature corresponding to change in distinctive acoustic properties. Moreover, density of all IBPIF kept at only 12−17 kg/m³. With increasing slurry temperature from 0 °C to 40 °C, cell size and window opening rate gradually increased from 553 μm to 791 μm and from 6.85% to 58.46%, respectively. In this study, IBPIF generated by slurries at 0 °C (marked as PIF-2) and 40 °C (marked as PIF-6) showed best and distinctive acoustic behavior in 315−800 Hz and 800−6300 Hz regions, respectively. After acoustic behavior study of combined IBPIF prepared by stitching combination between two distinctive acoustic IBPIFs, results showed that only when PIF-6 sheet used as sound receiving surface even though with thickness of only 10 mm could the combined IBPIF possess the best acoustic level in 800−6300 Hz region as PIF-6. Furtherly, acoustic behavior in 315−800 Hz region could be significantly enhanced by increasing thickness of PIF-2 and could reach or close to the best acoustic level.

The nanoparticle (NP) functionalization is an effective method for enhancing their compatibility with polymer which can influence the fracture property of the polymer nanocomposites (PNCs). This work aims to further understand the cavitation and crazing process, hoping to uncover the fracture mechanism on the molecular level. By adopting a coarse-grained molecular dynamics simulation, the fracture energy of PNCs first increases and then decreases with increasing the NP functionalization degree $ \alpha $ while it shows a continuous increase with increasing the interaction $ {{\varepsilon }_{\rm{pA}}}$ between polymer and modified beads. The bond orientation degree is first characterized which is referred to as the elongation. Meanwhile, the stress by polymer chains is gradually reduced with increasing the $ \alpha $ or the $ {{\varepsilon }_{\rm{pA}}}$ while that by NPs is enhanced. Furthermore, the percentage of stress by polymer chains first increases and then decreases with increasing the strain while that by NPs shows a contrast trend. Moreover, the number of voids is quantified which first increases and then decreases with increasing the strain which reflects their nucleation and coalescence process. The voids prefer to generate from the polymer-NP interface to the polymer matrix with increasing $ \alpha $ or $ {{\varepsilon }_{\rm{pA}}}$. As a result, the number of voids first increases and then decreases with increasing $ \alpha $ while it continuously declines with the $ {{\varepsilon }_{\rm{pA}}}$. In summary, our work provides a clear understanding on how the NP functionalization influences the cavitation and crazing process during the fracture process.

In this work, Monte Carlo simulations are used to study the critical adsorption behaviors of flexible polymer chains under the action of an external driving force F parallel to an attractive flat surface. The critical adsorption temperature T_c decreases linearly with increasing F, indicating that the driving force suppresses the adsorption of polymer. The conformation of polymer is also affected by the driving force. However, the effect of F is dependent on the competition between the driving force and temperature. Under strong force or at low temperature, the polymer is stretched along the direction of the force, while under weak force or at high temperature, the polymer is not stretched. When the force is comparable to the temperature, the polymer may be stretched perpendicular to the driving force, and below T_c, we observe conformational transitions from parallel to perpendicular and again to parallel by decreasing the temperature. We found that the perpendicular stretched conformation leads the polymer chain to synchronously move along the direction of the driving force. Moreover, the conformational transitions are attributed to the competition and cooperation between the driving force and the temperature.