Since electromagnetic pollution is detrimental to human health and the environment, numerous efforts have been successively made to achieve excellent electromagnetic interference shielding effectiveness (EMI SE) via designing the hierarchical structures for electromagnetic interference (EMI) shielding polymer composites. Among the plentiful structures, the asymmetric structures are currently a hot spot, principally categorizing into multi-layered, porous, fibrous, and segregated asymmetric structures, which endows the high EMI shielding performance for polymer composites incorporated with magnetic, conductive, and/or dielectric micro/nano-fillers, due to the “absorption-reflection-reabsorption” shielding mechanism. Therefore, this review provides the retrospection and summary of the efforts with respect to abundant asymmetric structures and multifunctional micro/nano-fillers for enhancing EMI shielding properties, which is conducive to the booming development of polymeric EMI shielding materials for the promising prospect in modern electronics and 5-generation (5G) technology.

The tacticity of vinyl polymers is a key factor affecting the properties of materials. Recently, organic Brønsted acids have been demonstrated as effective catalysts for the development of highly stereoselective cationic reversible addition-fragmentation chain transfer (RAFT) polymerizations of vinyl ethers, in which the use of RAFT agents could allow the control the molecular weight and tacticity of polymer products simultaneously. However, the effect of RAFT agents on the tacticity-regulation remains elusive and lacks of investigation. In this study, we synthesized four types of RAFT agents and evaluated their influence in the stereoselective cationic polymerization of isobutyl vinyl ether in the presence of PADI as a Brønsted acid catalyst, which unveils that the Z group of RAFT agents could not only affect the polydispersity of the products, but also exert a profound effect on the stereoselectivity. After extensive screening of the RAFT agents, high stereoregularity (isotacticity, 90% m) was obtained when using dithiocarbonate ester-type RAFT agents with a benzyloxy Z group.

Bacterial biofilms present a significant challenge in treating drug-resistant infections, necessitating the development of innovative nanomedicines. In this study, we introduce triclosan-conjugated, lipase-responsive polymeric micelles designed to exploit biofilm properties and serve as a responsive drug delivery platform. The micelles were created using an amphiphilic block polymer synthesized via ring-opening polymerization of ε-caprolactone (CL) and triclosan-containing cyclic trimethylene carbonate (MTC-Tri). Poly(ethylene glycol) (PEG-OH) acted as the macro-initiator, resulting in micelles with a PEG shell that facilitated their penetration into bacterial biofilms. An important advantage of our micelles lies in their interaction with local bacterial lipases within biofilms. These lipases triggered rapid micelle degradation, releasing triclosan in a controlled manner. This liberated triclosan effectively eliminated bacteria embedded in the biofilms. Notably, the triclosan-conjugated micelles displayed minimal toxicity to murine fibroblasts, indicating their biocompatibility and safety. This finding emphasizes the potential application of these micelles in combatting drug resistance observed in bacterial biofilms. Our triclosan-conjugated, lipase-responsive polymeric micelles exhibit promising characteristics for addressing drug resistance in bacterial biofilms. By harnessing biofilm properties and implementing a responsive drug delivery system, we seek to provide an effective solution in the fight against drug-resistant bacteria.

Against the backdrop of a global paper resource shortage, there is a growing need to identify fast-growing tree species capable of producing long-lasting paper. Three plant species namely Broussonetia kazinoki, Broussonetia papyrifera and hybrid paper mulberry, belong to the Broussonetia genus, were collected from China to study their white bark suitability for pulp and papermaking. Their chemical composition revealed that the holocellulose content in Broussonetia kazinoki and Broussonetia papyrifera was more than 80%. The molecular weight distribution of several holocellulose/α-cellulose is observed by GPC, which allows us to better observe the changes of various components on the molecular weight. The yield, lignin, whiteness, and molecular weight of the pulps obtained by NaOH treatment were determined. Optical microscope was used to characterize the fiber length-width ratio and rigidity. Finally, the improvement of the fiber rigidity method based on the Kratky-Porod chain model makes it more theoretical and further reveals the influencing factors of fiber rigidity. This study demonstrates the high potentiality of these three species for papermaking applications.

Poly(lactide acid) (PLA) foams have shown considerable promise as eco-friendly alternatives to nondegradable plastic foams, such as polystyrene (PS) foams. Nevertheless, PLA foam typically suffers from low heat-resistance and poor cellular structure stemming from its inherent slow crystallization rate and low melt strength. In this study, a high-performance PLA foam with well-defined cell morphology, exceptional strength and enhanced heat-resistance was successfully fabricated via a core-back microcellular injection molding (MIM) process. Differential scanning calorimetry (DSC) results revealed that the added hydrazine-based nucleating agent (HNA) significantly increased the crystallization temperature and accelerated the crystallization process of PLA. Remarkably, the addition of a 1.5 wt% of HNA led to a significant reduction in PLA’s cell size, from 43.5 μm to 2.87 μm, and a remarkable increase in cell density, from 1.08×10⁷ cells/cm³ to 2.15×10¹⁰ cells/cm³. This enhancement resulted in a final crystallinity of approximately 55.7% for the PLA blend foam, a marked improvement compared to the pure PLA foam. Furthermore, at 1.5 wt% HNA concentration, the tensile strength and tensile toughness of PLA blend foams demonstrated remarkable improvements of 136% and 463%, respectively. Additionally, the Vicat softening temperature of PLA blend foam increased significantly to 134.8 °C, whereas the pure PLA foam exhibited only about 59.7 °C. These findings underscore the potential for the preparation of lightweight injection-molded PLA foam with enhanced toughness and heat-resistance, which offers a viable approach for the production of high-performance PLA foams suitable for large-scale applications.

In this study, a series of hindered urea bond (HUB) containing polyurethane-urea methacrylate prepolymers and a none HUB containing polyurethane methacrylate prepolymer were prepared using isobornyl methacrylate as the reactive diluent via one-pot procedure. The prepolymers were characterized fully by various techniques. Then, their thermosets were fabricated via UV curing in presence of a photo initiator, and their mechanical property and thermal behavior were investigated and compared. Different from the none HUB containing thermoset, the HUB containing thermosets (defined as PUT) could be recycled and reprocessed by hot press under relatively mild conditions with high recovery ratio of mechanical property. Furthermore, zinc oxide (ZnO) nanoparticles were modified with 3-(trimethoxysilyl) propyl methacrylate and the modified ZnO (defined as ZnO-TPM) was dispersed and polymerized into PUT matrix to prepare their nanocomposites. The influence of ZnO-TPM on the mechanical performance of the composites was evaluated, which indicated that the Young’s modulus and tensile strength increased gradually to the maximum values at ZnO-TPM content of 1 wt% and then decreased. The composites also displayed good reprocessability with improved recovery ratio compared to the pure PUT sample. In addition, the composite materials exhibited strong UV absorption capacity, implying their potential application in the circumstance where UV-shielding was required.

Inkjet 3D printing has potential in the additive manufacturing of electronic circuits and devices. However, inks that can be used for printing layers with T_5%>300 °C or hardness>200 MPa have been rarely reported. Cyanate ester (CE) polymers have excellent thermal stability, high strength, and low shrinkage compared to other common dielectric inks for inkjet 3D printing, but cannot be quickly shaped by ultraviolet (UV) irradiation or thermal treatment. Combining CEs with UV-curable monomers may be a possible way to accelerate crosslinking, but there are challenges from the adverse effects of the dilution of both monomers. In this study, dielectric inks with acrylate and cyanate moieties were developed. The low viscosity and surface tension of the CE precursor (Bisphenol E cyanate ester) were combined with photocurable acrylate diluent monomers and cross-linker to realize an ink suitable for inkjet 3D printing. An internal dual three-dimensional cross-linked network structure resin was prepared by a combination of photocuring and thermal curing with T_5% up to 326.69 °C, hardness up to 431.84 MPa, dielectric constant of 2.70 at 8 GHz, and shrinkage of 1.64%. The developed dielectric inks can be applied to the 3D printing of printed circuit boards and other electronic devices that require dielectric properties.

For a polymer/polymer dismissible blend with two crystallizable components, the crystallization behavior of different components and the reciprocal influences between different crystals are interesting and important, but did not investigate in detail. In this study, the L-poly(lactic acid)/polypropylene (PLLA/PP) blends with different weight ratios were prepared by melt mixing and the crystallization behavior of the blends were investigated. Results showed that the crystalline structures of PLLA and PP were not altered by the composition. For the crystallization of PLLA, both the diffusion of chain segments and crystallization rate were enhanced under the existence of PP crystals. For the crystallization of PP, its crystallization rate was depressed under the existence of amorphous PLLA molecular chains. When the PP crystallized from the existence of PLLA crystals, although the diffusion rate of PP was reduced by PLLA crystals, the nucleation positions were obviously enhanced, which accelerated the formation of PP crystals. This investigation would supply more basic data for the application of PLLA/PP blend.

Various sectors of the industry are searching for new materials with specific requirements, providing improved properties. The study presents novel composite materials based on polylactide that have been modified with the organosilicon compound, (3-thiopropyl)polysilsesquioxane (SSQ-SH). The SSQ-SH compound is a mixture of cage structures and not fully condensed random structures. The composite materials were obtained through injection moulding. The study includes a comprehensive characterization of the new materials that analyze their functional properties, such as rheology (MFR), mechanical strength (tensile strength, Charpy impact strength), and thermal properties. SEM microscopic photos were also taken to analyze the microstructure of the samples. The addition of a 5% by-weight organosilicon compound to polylactide resulted in a significant increase in MFR by 73.8% compared to the neat polymer. The greatest improvement in impact strength was achieved for the 5% SSQ-SH/PLA composite, increasing it by 32.0 kJ/m² compared to PLA, which represents an increase of up to 187%. The conducted research confirms the possibility of modifying the properties of the polymer by employing organosilicon compounds.

Regulation of phase structure has been recognized as one of the most effective ways to fabricate self-healing polymers with high mechanical strength. The mechanical properties of the resultant polymers are certainly affected by the size of separated phase domain. However, the study on this aspect is absence, because it can hardly exclude the influence of variation in monomer proportion required for tuning the separated phase size. Here, we report the first study on tuning the phase size through reversible addition-fragmentation chain transfer (RAFT) polymerization without changing the proportion of monomers. As expected, the size of separated phase has been successfully mediated from 15 nm to 9 nm by tuning the molecular weight of the chain transfer agent. It is found that the mechanical strength and the self-healing efficiency of the resultant polymers increase simultaneously with the decrease of phase size. The study on the formation kinetics of hydrogen bonds reveals that the decrease of phase size can facilitate the re-bonding rate of hydrogen bonds, even if the migration of polymer chains is restricted.

In this work, poly(3-hexylthiophene) (P3HT) ultrathin films (P3HT-T) were prepared by spin-coating a dilute P3HT solution (in a toluene: o-dichlorobenzene (Tol:ODCB) blend with a volume ratio of 80:20) with ultrasonication and the addition of the nucleating agent bicycle [2.2.1] heptane-2,3-dicarboxylic acid disodium salt (HPN-68L) on glass, Si wafers and indium tin oxide (ITO) substrates. The electrical and mechanical properties of the P3HT-T ultrathin films were investigated, and it was found that the conductivity and crack onset strain (COS) were simultaneously improved in comparison with those of the corresponding pristine P3HT film (P3HT-0, without ultrasonication and nucleating agent) on the same substrate, regardless of what substrate was used. Moreover, the conductivity of P3HT-T ultrathin films on different substrates was similar (varying from 3.7 S·cm⁻¹ to 4.4 S·cm⁻¹), yet the COS increased from 97% to 138% by varying the substrate from a Si wafer to ITO. Combining grazing-incidence wide-angle X-ray diffraction (GIXRD), UV-visible (UV-Vis) spectroscopy and atomic force microscopy (AFM), we found that the solid order and crystallinity of the P3HT-T ultrathin film on the Si wafer are highest, followed by those on glass, and much lower on ITO. Finally, the surface energy and roughness of three substrates were investigated, and it was found that the polar component of the surface energy γ^p plays a critical role in determining the crystalline microstructures of P3HT ultrathin films on different substrates. Our work indicates that the P3HT ultrathin film can obviously improve the stretchability and simultaneously retain similar electrical performance when a suitable substrate is chosen. These findings offer a new direction for research on stretchable CP ultrathin films to facilitate future practical applications.

Rubbers or elastomers play an important role in hi-tech technology and civilian daily life because of their unique and strategical properties. Generally, the rubber additives are essential components for rubbers' practical application. Nowadays, developing novel multifunctional additives has attracted increasing research attention. In this work, low-cost crude carbon dots (CCDs) were used as multifunctional additives for natural rubber/silica system (without any additional modification) through industrial compatible melt-mixing method. The results revealed that the CCDs could disperse well in the NR/silica system, and they could not only endow the rubber compound with excellent anti-aging capability due to CCDs' radical scavenging activity because of their plenty of nitrogen-containing species, but also improve the curing rate and mechanical performance of the rubber composite. Also, the CCDs could reduce the rolling resistance of the rubber composites (tanδ value at 7% strain of the rubber composite could be decreased by 34%), which is promising for the application of energy-saving tire industry. Lastly, the addition of CCDs could effectively reduce the ZnO dosage by at least 40% in the rubber composite without deteriorating its performance. Overall, this work provides valuable guidance to develop novel cheap yet effective additives for the elastomer.

Non-aromatic fluorescent and multi-responsive materials, exhibiting inherent fluorescence emission and controlled phase change, have garnered significant attention in recent years. However, the underlying interaction between their fluorescent properties and phase transition remains unclear. In this study, we synthesized a series of catalyst-free aza-Michael addition-based polyethyleneimine (RFPEI) materials by reacting polyethyleneimine (PEI) with N-isopropyl acrylamide (NIPAM). The resulting RFPEI was comprehensively characterized, and demonstrated dual-phase transition behavior (LCST and UCST) in water, which could be finely tuned by adjusting its composition or external factors such as pH. Notably, upon UV irradiation (365 nm), RFPEI exhibited strong fluorescence emission. We further investigated the effects of NIPAM grafting percentage to PEI, polymer concentration, and pH on the LCST/UCST and fluorescent properties of RFPEI aqueous solutions. Moreover, we showcased the great potential of RFPEI as a versatile tool for physiological cell imaging, trace detection, and controlled release of doxorubicin. Our study presents a novel class of stimuli-responsive fluorescent materials with promising applications in the field of biomedicine.

In order to achieve efficient and durable oil-water emulsion separation, the membranes possessing high separation efficiency and mechanical strength attract extensive attention and are in great demand. In present study, a kind of polytetrafluoroethylene (PTFE)-based bilayer membrane was fabricated by electrospinning fibrous PTFE (fPTFE) on an expanded PTFE (ePTFE) substrate. The morphological observation revealed that the fibrous structure of the fPTFE layer could be tailored by controlling the formulation of spinning solution. The addition of appropriate polyoxyethylene (PEO) would make the fibers in the fPTFE layer finer and more uniform. As a result, the compounded membrane exhibited a small pore size of approximately 1.25 μm and a substantial porosity nearing 80%. This led to super-hydrophobicity, characterized by a high water contact angle (WCA) of 149.8°, and facilitated rapid oil permeation. The water-in-oil emulsion separation experiment further confirmed that the compounded membrane not only had a high separation efficiency closing 100%, but such an outstanding separation capacity could be largely retained, either through multiple cycles of use or through strong acid (pH=1), strong alkali (pH=12), or high-temperature (100 °C) treatment. Additionally, the mechanical behavior of the bilayer membrane was basically contributed by that of each layer in terms of their volume ratio. More significantly, the poor creep resistance of fPTFE layer was suppressed by compounding with ePTFE substrate. Hence, this study has laid the groundwork for a novel approach to create PTFE-based compounded membranes with exceptional overall characteristics, showing promise for applications in the realm of emulsion separation.

To enhance the mechanical properties of polypropylene random copolymer (PPR), polystyrene (PS) with four different contents were added to the PPR matrix through melt blending. Subsequently, using the Multi-Flow Vibration Injection Molding (MFVIM) technology, PPR/PS in situ microfiber composites (MFC) with different blending ratios were prepared. The results indicated that blending ratio had a great impact on the phase morphology and crystal structure of MFVIM samples, which was different from those of conventional injection molding (CIM) samples. PS ultrafine fibers could be formed under the shear field and could absorb the PPR molecular chains to form hybrid shish-kebab structures. Meanwhile, the PPR matrix could also form shish-kebab structures under the effect of strong shear. When the PS content reached 20%, under the combined action of PS in situ microfibers and highly oriented crystal structure, the tensile strength and Young's modulus of the sample were obviously improved and the impact strength remained at a relatively high level. So a strong and tough balanced PPR based material was obtained. These results provide valuable insights for expanding the industrial and daily-life applications of PPR and show promising development prospects.

In this study, flexible and highly conductive composite rubber at low filler content was successfully prepared through polydopamine-assisted electroless silver plating plus mechanical mixing. Firstly, carbon fibers (CF) were activated by polydopamine (PDA) to improve the surface activity by self-polymerization reaction. Next, because of the metal chelating ability of PDA, silver layer was firmly deposited on the surface of CF through a facile electroless silver plating method. Finally, flexible silver-plated carbon fibers (Ag/pCF) silicone rubber composites prepared by mechanical mixing. By using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), the chemical composition and crystal structure of Ag/pCF were examined, and scanning electron microscopy (SEM) was used to assess the surface morphology of the Ag/pCF. The results showed that a uniform and dense silver layer was formed on the surface of the CF, and the conductivity of the Ag/pCF could reach 7885 S/cm. It was noteworthy that the composite rubber filled with only 45 phr Ag/pCF had a high electromagnetic interference shielding effectiveness (100 dB) due to the low density and high aspect ratio of Ag/pCF. The composite rubber has excellent potential for application in the field of electromagnetic interference shielding.

The mechanical behavior of polymer networks is intrinsically correlated with the local chain topology and chain connectivity. In this study, we delve into this relationship through the lens of coarse-grained molecular dynamics (CG-MD) simulations. Our aim is to illuminate the intricate interplay between local topology and stress distribution within polymer monomers, cross-linkers, and various components with distinct cross-link connections, thereby elucidating their collective impact on the mechanical properties of polymer networks. We mainly focus on how specific local structures contribute to the overall mechanical response of the network. In particular, we employ local stress analysis to unravel the mechanics of these structures. Our findings reveal the diverse responses of individual components, such as junctions, strands, cross-linkers between junctions, and dangling chain ends, when subjected to stretching. Notably, we observe that these components exhibit varying degrees of deformation tolerance, underscoring the significance of their roles in determining the mechanical characteristics of the network. Our investigations highlight junctions as primary contributors to stress accumulation, and particles with higher local stress showing a stronger correlation between stress and Voronoi volume. Moreover, our results indicate that both strands and cross-linkers between junctions exhibit heightened stress levels as strand lengths decrease. This study enhances our understanding of the multifaceted factors governing the mechanical attributes of cross-linked polymer systems at the microstructural level.

The injection of a polymer chain into a small circular cavity under tangential self-propelled force is studied by using Langevin dynamics simulation. Results indicate that the injection dynamics of the active polymer shows strong correlation with the polymer conformation inside the cavity depending on the polymer rigidity (k_b). The injection time τ varies nonmonotonously with increasing k_b, and reaches its minimum at k_b^*. When k_b is small (k_b << k_b^*), the polymer is nearly random coil in the cavity, and spends a long time at the final stage of the injection process due to the large repulsion between monomers inside the cavity. When k_b is moderate (k_b ~ k_b^*), the part of polymer inside the cavity forms spiral configuration under the tangential active force, and the whole polymer moves synchronously with a constant velocity during the injection process, leading to a small injection time. When k_b is large (k_b >> k_b^*), the polymer is nearly straight at the initial stage of the injection process, and takes a long time to bend itself, leading to a large injection time.