Conductive polymer composites (CPCs) are widely used in the field of organic electronics as the material basis of high-performance devices, due to their obvious advantages including electrical conductivity, lightness, processability and so on. Research on CPCs has focused on the enhancement of their electrical features and the exploration of their application prospects from conventional fields to heated emerging areas like flexible, stretchable, wearable, biological and biomedical electronics, where their mechanical properties are quite critical to determine their practical device performances. Also, a main challenge to ensure their safety and reliability is on the synergistic enhancement of their electrical behavior and mechanical properties. Herein, we systematically review the research progress of CPCs with different conductive fillers (metals and their oxides, carbon-based materials, intrinsically conductive polymers, MXenes, etc.) relying on rich material forms (hydrogel, aerogel, fiber, film, elastomer, etc.) in terms of mechanical property regulation strategies, mainly relying on optimized composite material systems and processing techniques. A summary and prospective overview of current issues and future developments in this field also has been presented.

Metal-backboned polymers with anisotropy microstructures are promising for conductive, optoelectronic, and magnetic functional materials. However, the structure-property relationships governing the interplay between the chemical structure and electromagnetic property of the metal-backboned polymer have been rarely investigated. Here we report a carbon/nickel hybrid from metal-backboned polymer to serve as electromagnetic wave-absorbing materials, which exhibit high microwave absorption capacity and tunable absorption band. The presence of nickel backbones promote the generation of heterogeneous interfaces with carbon during calcination, thereby enhancing the wave-absorbing capacity of the carbon/nickel hybrid. The C/Ni hybrids show a minimal reflection loss of −49.1 dB at 13.04 GHz, and its frequency of the absorption band can be adjusted by controlling the thickness of the absorption layer.

Anion-exchange membranes (AEMs) with high conductivity and stability are essential components of hydrogen related water electrolysis and fuel cell applications. During the past decades, polynorbornene (PNB)-based AEMs have shown excellent performance due to their saturated all-carbon-based backbones and diverse strategies to prepare cross-linked membranes. However, nearly all previously reported PNB-based AEMs rely on the alkyl-substituted norbornene monomers, whose low-yielding synthesis leads to high-cost of the AEMs. In addition, the cross-linked PNB-based AEMs usually suffered from mechanical brittleness. Herein, we propose a novel semi-interpenetrating polymer network (s-IPN) strategy to simultaneously enhance mechanical modulus and ionic conductivity, while using commercial 5-vinyl-2-norbornene (VNB) as the single norbornene derivatives to prepare high-performance AEMs. A diallylphenol quaternary ammonium salt was used for photo-induced cross-linking with poly-VNB and various dithiols to produce AEMs with s-IPN structures. The resultant membranes have excellent hydroxide conductivities and alkaline stability in 1 mol/L KOH at 80 °C, and are successfully applied in alkaline anion-exchange membrane water electrolyzers to stably operate for over 150 h.

Conjugated polymers are mainly synthesized by cross-coupling polymerizations catalyzed with transition metal (Pd, Ni) catalysts through step-growth polymerization (SGP) mechanism. According to the classical theory of SGP, the polymer dispersion index (Ð) of the synthesized polymers will never be higher than 2. However, the cases where conjugated polymers synthesized with Ð value far exceeding 2 are very common in reality, which severely limits their processing property, performance and applications. To investigate the reason behind the Ð value deviation from the theoretical value of SGP, direct arylation polycondensation (DArP) of 2-bromo-3-hexylthiophene (3HT) was chosen as the model reaction, and the reaction process was tracked using gel permeation chromatography analysis. When Pd(OAc)₂ was used as the catalyst, the Ð value linearly increased with the increase of the weight-average molecular weight (M_w) of polymer (P3HT) after a short period and reached up to 7.2 at prolonged reaction time. Scanning transmission electron microscopic images of the reaction mixture showed the fibril-like aggregation of P3HT and assembling of Pd species in P3HT aggregates. A catalyst competition mechanism was thus proposed, together with numerical calculation, giving a good fitting to the experimental results, which is believed to have far-reaching significance for guiding the design, synthesis and processing of conjugated polymers.

A series of transparent crosslinked colorless polyimide (CPI) films are prepared from 3,3’,4,4’-biphenyltetracarboxylic dianhydride (BPDA), 2,2’-bis(trifluoro-methyl)benzidine (TFMB), and 4,4’-oxydianiline (ODA) by thermal imidization, incorporating varying contents of 2,2'-(1,3-phenylene)bis(2-oxazoline) (1,3-PBO) as the crosslinking agent. Following the incorporation of the crosslinking structure, the CPI films show good optical transparency (approximately 85% winthin visible light range), enhanced glass transition temperature (from 325 °C to 341 °C), and improved thermal stability, and tensile strength. Notably, compared with the pristine uncrosslinked CPI, these crosslinked CPI films significantly increase in elongation at break (from 5.4% to 44.2%). Furthermore, the new approach ensures that crosslinked CPIs improve heat resistance and mechanical properties, while avoiding the embrittlement of materials. This study also offeres straightforward preparation methods for optically transparent crosslinked polyimides without additional processing steps. All these results make this approach can effectively improve the competitive performance of the CPI films for potential applications in microelectronic and optoelectronic fields.

Photonic materials, which react to light, have garnered interest due to their capability to exhibit adjustable structural colors. Typically, light targets the UV, visible, or near-IR spectrums. In this study, microgel-based photonic materials that are capable of reversibly responding to X-rays have been engineered. To accomplish this, azobenzene (Azo)-containing poly(N-isopropylacrylamide) (pNIPAm)-based microgels are synthesized. Subsequently, ZnS scintillator and Cr/Au are applied on each side of the poly(methyl methacrylate (PMMA) substrate. Subsequently, the Azo MG monolayer is deposited onto the Au surface, followed by the deposition of an additional layer of Cr/Au. This process generates ZnS/PMMA/Cr/Au/Azo MG/Cr/Au or ZnS/Au-Azo MG-Au structure. Functioning as a typical interferometer, ZnS/Au-Azo MG-Au demonstrates tunable colors based on the separation distance between the two Au layers. The ZnS scintillator can absorb and convert X-rays into UV light, initiating the transition of the Azo groups from a trans to a cis state. Consequently, this transition causes the Azo MG to swell. As Azo MG swells, the distance between the two Au layers increases, resulting in a red-shift of approximately 350 nm in the optical signal of the ZnS/Au-Azo MG-Au interferometer. Remarkably, this X-ray responsivity of the interferometer is reversible, as it returns to its initial state after being stored in the dark for 24 h. To demonstrate its capabilities, the ZnS/Au-Azo MG-Au interferometer successfully releases a drug when triggered by X-ray stimulation, thus validating its potential. The microgel-based interferometers hold significant promise for applications in chemoradiotherapy, radiobiology, and actuators in space.

Organocatalysis has shown special potency for simplifying the construction of complex polymer structures. We are reporting here a one-pot synthetic pathway using amine as a selectivity-switching agent in the two-component catalytic system consisting of triethylborane (Et₃B) and a phosphazene base. We first modelled the interactions of a variety of amines with Et₃B by density functional theory calculations. The results indicate that the aliphatic diamines comprising both primary and tertiary amino groups, capable of forming stable intramolecular hydrogen bonds, undergo the strongest complexation with Et₃B. Accordingly, experimental results demonstrate that the addition of such amines promptly actuates the in situ selectivity switch from Lewis pair-catalyzed ring-opening polymerization (ROP) of epoxide (propylene oxide, n-butylglycidyl ether, or glycidyl phenyl ether) to organobase-catalyzed ROP of δ-valerolactone, allowing one-pot continuous synthesis of ether-ester type block copolymers. We thus exploited the noncovalent interaction between amine and Et₃B to refine the catalyst switch strategy by exempting it from loading of extra catalyst.

Moderate ultraviolet (UV) radiation from sunlight is essential for human health, but overexposure to UV rays can cause serious adverse effects. It is important to detect UV radiation from sunlight in time to prevent damage from excessive exposure. Here, a ready-to-use, easy-to-interpret, inexpensive, reusable, and wearable all-in-one UV monitoring and shielding sensor SP-TPE@PU textile has been developed. The SP-TPE@PU textiles are constructed by photochromic molecule SP-TPE and commercial polymer polyurethane (PU) through electrospinning. The SP-TPE molecule acts as the sensor component, and PU contributes to high flexibility. The SP-TPE@PU textiles show remarkable durability (against repeated twisting, curling, bending deformations, and water immersion) and good permeability, making them durable and breathable wearable materials. When exposed to sunlight, the SP-TPE@PU textiles rapidly exhibit significant color changes due to the efficient isomerization of SP-TPE, serving as an early warning and monitoring of UV radiation. In addition, the SP-TPE@PU textiles can revert to the initial state with visible light irradiation for reuse. Furthermore, the SP-TPE@PU textiles possess excellent UV shielding ability, contributing to human body protection. Simple and easy operation, significant and reversible color changes, good breathability and mechanical properties make SP-TPE@PU textiles reusable and wearable all-in-one UV monitoring and shielding sensors.

Copolyfluorenes are of great interest due to their ability to form thin films with tunable optical and electrical properties. In this paper, copolymers of polyfluorene with electron withdrawing dicyanostilbene and dicyanophenanthrene moieties were synthesized; their thin films were characterized by electron spectroscopy, cyclic voltammetry, electrical, and photoelectrical measurements. The mobility of charge carriers in the copolymers was measured for the first time, with the acceptor components providing balanced electron and hole mobilities of the order of 10⁻⁶ cm²·V⁻¹·s⁻¹. Photodetectors based on the copolymer/PTCDI heterojunction exhibited the photoresponse band extended into the green region due to the absorption of PTCDI and an increased photocurrent in the UV-blue absorption band of the copolymer, which is related to the absorption of photoluminescent emission of the copolymers in PTCDI. The presented approach to improving the performance of a polymer-based photodetector is promising in organic optoelectronics.

Star-shaped poly(lactic acid)s (PLAs) with two to five arms were synthesized by ring opening polymerization using tin(II) 2-ethylhexanoate as catalyst and polyols as initiators. The effects of molecular weight together with multi-arm architecture on crystallization behavior, spherulite morphology and alkaline degradation behavior of star-shaped PLAs have been investigated. The results indicate that the multi-arm architecture interfered with spherulite growth, but promoted nucleation and alkaline degradation of star-shaped PLAs. Interestingly, with the increase of molecular weight (M_n), the crystallization rate first increased and then decreased, while the alkaline degradation rate was the opposite. The characteristic crystallization and alkaline degradation behavior of star-shaped PLAs were discussed based on the competition between segmental mobility and central core confinement.

In this study, we prepared unentangled and slightly entangled poly(_L-lactic acid) telechelic ionomer samples (M_n=5 and 16 kg/mol) based on sodium sulfonate groups. The telechelic samples exhibit extremely slow crystallization kinetics below the melting temperature T_m and above the glass transition temperature T_g, which enables us to examine the linear viscoelasticity of the ionomer melt samples therein. The application of either the shear flow (at 85 °C) or elongational flow (between 70 and 90 °C) strongly accelerates the crystallization, leading to strong strain hardening and formation of highly oriented α crystals. Depending on the relative average rates of the strain-induced dissociation and strain-induced crystallization, the stress evolution can be classified into two cases, and the critical work for strain-induced crystallization is higher in case where the strain-induced dissociation occurs earlier than the strain-induced crystallization.

In particle-filled polymer composites with selective distributions of fillers in one phase, much attention has been focused on the "volume exclusion effect" in reducing the percolation threshold of filler, while the role of dispersed polymer phase acting as bridges of fillers in the particle network has largely been ignored. Herein, we studied industrially important ternary composites, polypropylene (PP)/ethylene-octene copolymer (a polyolefin elastomer, POE)/talc systems, and adopted rheology to reveal the bridging behavior of POE droplets in the network of talc particles. It is found that talc fillers concentrate in the PP phase using the "blend first" protocol, while more talc particles are located at the interface of PP and POE phases using the "filler first" protocol. Changing the POE viscosity and talc size can affect the migration of talc from the POE phase to the PP phase in the "filler first" protocol. The linear rheology behavior indicates that besides the "volume exclusion effect", the talc-POE hybrid network can further contribute to the reinforcement effect. Meanwhile, the POE droplet bridging structure can facilitate the rebuilding of the hybrid network after large amplitude oscillatory shear, in contrast to the un-recoverable structures in the PP/talc binary composites. The correlation between rheology and selective distribution of fillers in ternary composites may provide practical guidance for processing and designing advanced polymer composites with controlled selective location of fillers.

Viscoelastic properties of thermoplastic polyurethane (TPU) is of fundamental importance for its processing. In this work, we prepared different TPUs from polycaprolactone (PCL) diol, diphenylmethane-4,4′-diisocyanate (MDI), and 1,4-butanediol (BDO), and investigated the viscoelastic behavior of three TPUs with different hard segment content during thermal annealing process. The storage modulus (G′) of TPU increases over time in a medium annealing temperature (T_a) region, but remains unchanged at both high and low temperature regions. The growth of loss modulus (G″) over time is slower than that of G′. At medium T_a, both G′ and G″ increase during the repeating frequency (ω) sweep, due to the gradual crystallization of hard segments. This indicates that the crystallites primarily restrain the relaxation of unit with large size. The increments of G′ and G″ are weakened when the content of hard segment in TPU is decreased. For TPU with high content of hard segments, a complete high elastic platform with a width of 3 orders of magnitude was observed only through one frequency scan test at medium T_a. In addition, the crystallites of hard segments grow up continuously during frequency scan test (isothermal annealing treatment) and cause the extreme increase in G′ and G″ with ω in low ω region.

The quest for scalable integration of monolayer graphene into functional composites confronts the bottleneck of high-fidelity transfer onto substrates, crucial for unlocking graphene's full potential in advanced applications. Addressing this, our research introduces the camphor-assisted transfer (CAT) method, a novel approach that surmounts common issues of residue and structural deformation endemic to existing techniques. Grounded in the sublimation dynamics of camphor, the CAT method achieves a clean, contiguous transfer of centimeter-scale monolayer graphene onto an array of polymer films, including ultra-thin polyethylene films. The resultant ultrathin graphene-polyethylene (gPE) films, characterized by their exceptional transparency and conductivity, reveal the CAT method's unique ability to preserve the pristine quality of graphene, underscoring its practicality for preparing flexible transparent electrodes by monolayer graphene. In-depth mechanism investigation into the camphor sublimation during CAT has led to a pivotal realization: the porosity of the target polymer substrate is a determinant in achieving high-quality graphene transfer. Ensuring that camphor sublimates initially from the polymer side is crucial to prevent the formation of wrinkles or delamination of graphene. By extensive examination of CAT on a spectrum of commonly used polymer films, including PE, PP, PTFE, PI and PET, we have confirmed this important conclusion. This discovery offers crucial guidance for fabricating monolayer graphene-polymer composite films using methods akin to CAT, underscoring the significance of substrate selection in the transfer process.

An improved X-ray apparatus that combines tensile testing and X-ray diffraction has been designed and constructed to conduct time-resolved experiments during uniaxial stretching. By utilizing mortise-like clamping jaws and dogbone-shaped specimens, this setup allows for the simultaneous recording of high-quality mechanical responses and 2D diffraction patterns due to the minimization of experimental errors from sample slippage or premature fracture. Furthermore, the local extension ratio can be accurately determined based on thickness variation, and the Hermans' orientation function was demonstrated to be a reliable method with high accuracy to calculate the segmental orientation parameter $\langle $P₂$\rangle $ in elastomeric samples under high degree of stretching. In summary, this innovative tensile-WAXD instrument has proven to be a promising and powerful technique for investigating the “stress-deformation-segmental orientation” relationship in elastomers with high extensibilities.

Melt pre-shear induced crystallization of polymer blends holds great significance in industrial processing and product application. In this work, two typical PB/PP blends (50/50, 90/10), possessing commercial value and academic hotspot, were employed to investigate the effect of melt pre-shear on the crystallization of isotactic poly(1-butene) (PB) and polypropylene (PP) by applying shearing slightly above the melting temperature of PP with subsequent non-isothermal crystallization to simulate actual processing conditions. It was discovered that in PB/PP (90/10) blend, in situ melt pre-shear generated oriented PP precursors induced the formation of PP-FIC (Flow-induced crystallization) which acted as row crystal nucleus significantly promoting PB crystallization into spherulite with higher melting temperatures (T_m), crystallinity (X_c), and thicker lamellar thickness (d_c). While in PB/PP (50/50) blend, the melt pre-shear generated PP-shish precursors induced the formation of PP shish-kebab that exerted a confining effect on the crystal growth of PB, resulting in truncated spherulite formation with higher T_m and thicker d_c but lower X_c. This research provides insight into the mechanism underlying oriented crystal structure formation, crystal properties, and phase morphology of PB/PP blends under melt pre-shear fields, which have significant theoretical and practical implications for their industrial processing and preparation of high-performance products.

Using molecular dynamics (MD) simulations, this study explores the fluid properties of three polymer melts with the same number of entanglements, Z, achieved by adjusting the entanglement length N_e, while investigating the evolution of polymer melt conformation and entanglement under high-rate elongational flow. The identification of a master curve indicates consistent normalized linear viscoelastic behavior. Surprising findings regarding the steady-state viscosity at various elongational rates (Wi_R>4.7) for polymer melts with the same Z have been uncovered, challenging existing tube models. Nevertheless, the study demonstrates the potential for normalizing the steady-state elongational viscosity at high rates (Wi_R>4.7) by scaling with the square of the chain contour length. Additionally, the observed independence of viscosity on the elongational rate at high rates suggests that higher rates lead to a more significant alignment of polymer chains, a decrease in entanglement, and a stretching in contour length of polymer chains. Molecular-level tracking of tagged chains further supports the assumption of no entanglement under rapid elongation, emphasizing the need for further research on disentanglement in polymer melts subjected to high-rate elongational flow. These results carry significant implications for understanding and predicting the behavior of polymer melts under high-rate elongational flow conditions.

Recent experimental observations of knotting in DNA and proteins have stimulated the simulation studies of polymer knots. Simulation studies usually identify knots in polymer conformations through the calculation of the Alexander polynomial. However, the Alexander polynomial cannot directly discriminate knot chirality, while knot chirality plays important roles in many physical, chemical, and biological properties. In this work, we discover a new relationship for knot chirality and accordingly, develop a new algorithm to extend the applicability of the Alexander polynomial to the identification of knot chirality. Our algorithm adds an extra step in the ordinary calculation of the Alexander polynomial. This extra step only slightly increases the computational cost. The correctness of our algorithm has been proved mathematically by us. The implication of this algorithm in physical research has been demonstrated by our studies of the tube model for polymer knots. Without this algorithm, we would be unable to obtain the tubes for polymer knots.

The performance and corresponding applications of polymer nanocomposites are highly dominated by the choice of base material, type of fillers, and the processing ways. Carbon black-filled rubber composites (CRC) exemplify this, playing a crucial role in various industries. However, due to the complex interplay between these factors and the resulting properties, a simple yet accurate model to predict the mechanical properties of CRC, considering different rubbers, fillers, and processing techniques, is highly desired. This study aims to predict the dispersion of fillers in CRC and forecast the resultant mechanical properties of CRC by leveraging machine learning. We selected various rubbers and carbon black fillers, conducted mixing and vulcanizing, and subsequently measured filler dispersion and tensile performance. Based on 215 experimental data points, we evaluated the performance of different machine learning models. Our findings indicate that the manually designed deep neural network (DNN) models achieved superior results, exhibiting the highest coefficient of determination (R²) values (>0.95). Shapley additive explanations (SHAP) analysis of the DNN models revealed the intricate relationship between the properties of CRC and process parameters. Moreover, based on the robust predictive capabilities of the DNN models, we can recommend or optimize CRC fabrication process. This work provides valuable insights for employing machine learning in predicting polymer composite material properties and optimizing the fabrication of high-performance CRC.

Nanopore sequencing harnesses changes in ionic current as nucleotides traverse a nanopore, enabling real-time decoding of DNA/RNA sequences. The instruments for the dynamic behavior of substances in the nanopore on the molecular scale are still very limited experimentally. This study employs all-atom molecular dynamics (MD) simulations to explore the impact of charge densities on graphene nanopore in the translocation of single-stranded DNA (ssDNA). We find that the magnitude of graphene’s charge, rather than the charge disparity between ssDNA and graphene, significantly influences ssDNA adsorption and translocation speed. Specifically, high negative charge densities on graphene nanopores are shown to substantially slow down ssDNA translocation, highlighting the importance of hydrodynamic effects and electrostatic repulsions. This indicates translocation is crucial for achieving distinct ionic current blockades, which plays a central role for DNA sequencing accuracy. Our findings suggest that negatively charged graphene nanopores hold considerable potential for optimizing DNA sequencing, marking a critical advancement in this field.

Machine learning-assisted prediction of polymer properties prior to synthesis has the potential to significantly accelerate the discovery and development of new polymer materials. To date, several approaches have been implemented to represent the chemical structure in machine learning models, among which Mol2Vec embeddings have attracted considerable attention in the cheminformatics community since their introduction in 2018. However, for small datasets, the use of chemical structure representations typically increases the dimensionality of the input dataset, resulting in a decrease in model performance. Furthermore, the limited diversity of polymer chemical structures hinders the training of reliable embeddings, necessitating complex task-specific architecture implementations. To address these challenges, we examined the efficacy of Mol2Vec pre-trained embeddings in deriving vectorized representations of polymers. This study assesses the impact of incorporating Mol2Vec compound vectors into the input features on the efficacy of a model reliant on the physical properties of 214 polymers. The results will hopefully highlight the potential for improving prediction accuracy in polymer studies by incorporating pre-trained embeddings or promote their utilization when dealing with modestly sized polymer databases.

Mechanical properties of polymers can be regulated by changing the numbers of hydrogen bonds and entanglement points. However, the interplay between hydrogen bond network and entangled network during stretching has not been fully studied. We performed molecular dynamics simulations to investigate the changes of hydrogen bonds and entanglements during stretching. The stretching causes the orientation of local segments, leading to the entanglement sliding and disentanglements at different strain regions. Then, the number of entanglement points keeps constant at first and then decreases with increasing strain. Differently, the orientation of local segments can cause the change of chain conformation, which leads to the breakage of hydrogen bonds. Thus, the number of hydrogen bonds decreases with the increase of strain. Simulation results also demonstrated that the number of hydrogen bonds decreases faster during stretching in systems containing more entanglements. In systems with different hydrogen bond site contents, the initial number of entanglement nodes and its decline range during stretching increase firstly and then decrease with the increase of hydrogen bond site content.