Chinese Journal of Polymer Science最新文献

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.

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.

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.

This study delves into the pivotal role of sulfur vulcanization in defining the mechanical characteristics of natural rubber (NR) latex-dipped products. Utilizing sulfur vulcanization, known for its operational simplicity and cost-effectiveness, we examine its ability to enhance product elasticity and mechanical strength through various sulfidic bond formations such as mono-, di-, and polysulfidic bonds. Different vulcanization systems and sulfur contents were evaluated for their influence on the mechanical attributes of latex films, employing three types of NR latex, namely concentrated NR (CNR), deproteinized NR (DPNR), and small rubber particle NR (SRP), each representing distinct non-rubber components (NRCs). The study utilized advanced atomic force microscopy (AFM) equipped with PeakForce Quantitative Nanomechanical Mapping (QNM) to visualize and measure Young’s modulus distribution across the film of pre-vulcanized latex. Our findings reveal that films by CNR processed using the conventional vulcanization (CV) system exhibited enhanced tensile strength and elongation at break. It even showed a lower crosslink density than those processed using the efficient vulcanization (EV) system. Interestingly, DPNR films showed a more uniform distribution of Young’s modulus, correlating well with their superior mechanical strength. In contrast, SRP films showed excessive network structure formation in the particles due to accelerated vulcanization rates, hampering subsequent post-vulcanization interparticle crosslinking in film formation and remaining more rigid. The overall results Illustrate clearly that the ultimate mechanical properties of the latex films are strongly dependent on the type of sulfidic bonds formed. This research reveals further the very intricate relationship between the vulcanization methods, sulfur content, and latex type in optimizing the mechanical performance of NR latex products. It provides valuable insights for industry practices aimed at improving the quality and performance of latex-dipped goods.

Although Ziegler-Natta (Z-N) polyolefins have been widely used as raw materials to produce pharmaceutical or food packaging, the migration of acid scavengers, an additive usually introduced in Z-N polyolefins, from the packaging to its contents has not been reported. In this work, the migration of the two most used acid scavengers, calcium stearate (CaSt₂) and zinc stearate (ZnSt₂), from a Z-N polypropylene random copolymer (PPR) into water during autoclaving at 121 °C were comparatively investigated. It was found that, for PPR plates containing 0.1 wt% CaSt₂ or ZnSt₂ (PPR-0.1CaSt₂, PPR-0.1ZnSt₂, respectively), the concentration of migrated calcium ion into water increased with autoclaving time, while that of zinc ion was much lower at same treatment durations and did not show a significant increase with treatment time. Interestingly, after removing all plates and acidification treatment, a considerable amount of stearic acid was detected in sterilized water for PPR-0.1ZnSt₂, but no such significant stearic acid was detected in sterilized water for PPR-0.1CaSt₂. Based on the structural evolution of the two soaps upon heating, possible mechanisms for the different migration behavior of CaSt₂ and ZnSt₂ from PPR into water during autoclaving treatment were proposed. Our results suggest that the migration issue of acid scavengers is worthy of attention in pharmaceutical packaging materials produced from Z-N polyolefins.

Polyelectrolytes (PEs) are polymers carrying ionizable groups along the chain backbone and play an important role in life and environmental sciences, industrial applications and other fields. Due to the complicated topological structure and electrostatic correlations of PEs, PEs exhibit very rich phase behavior and morphologies in both bulk and confined solutions. So far, many theories, simulations and machine learning approaches have been proposed to study the behavior of polyelectrolyte solutions, especially the intrinsic structure-property relationships. In this perspective, from a personal point of view, we present several recent trends in polyelectrolyte solutions. The main themes considered here are accelerated development of sequence-defined polyelectrolyte (SDPE) via artificial intelligence technology, liquid-liquid phase separation in bulk SDPE solutions, adsorption behaviors of SDPE in the vicinity of a single dielectric surface, and surface forces between two charged surfaces mediated by SDPE solutions.

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.

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.

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 timeresolved 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 〈P₂〉 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.