Chinese Journal of Polymer Science最新文献

The equilibrium melting point (T_m⁰) is a crucial thermodynamic parameter for characterizing the crystallization and melting behavior of semi-crystalline polymers. However, the direct measurement of T_m⁰ poses a significant challenge because of the difficulty in physically fabricating fully-extended chain crystals of high-molecular-weight polymers. Therefore, various extrapolation equations for T_m⁰ have been proposed that utilize the thermal properties of ordinary folded-chain lamellae. Among these, the Gibbs-Thomson equation is one of the most commonly employed for modeling. Despite its widespread use, there are notable variations in the T_m⁰ values obtained by different research groups, even when based on similar samples. This raises questions about the validity and accuracy of using the Gibbs-Thomson equation to linearly extrapolate T_m⁰. In this study, we prepared a series of oligomer extended-chain crystals (ECCs) of poly(butylene succinate) (PBS) and used their properties for Gibbs-Thomson fitting. The results reveal a perfect linear relationship, with an extrapolated T_m⁰ value of 136.08 °C. The basal surface free energy of the oligomer ECCs was calculated as 0.084 J/m², which is approximately twice that of folded-chain lamellae. This difference is attributed to the aggregation of highly mobile free tails on the crystal surface. The two structural features of oligomer ECCs—large thickness and fixed surface—better fulfill the conditions for applying the Gibbs-Thomson equation, ensuring its validity and accuracy. Therefore, we believe that the Gibbs-Thomson fit can produce reliable results when sufficient high-quality data are used.

Porous phase-inversion membranes of complex morphology were obtained on the basis of aromatic polyamidoimides with different numbers of hydroxyl groups in the diamine component of the repeating unit. The influence of the quality of the precipitant (nonsolvent) applied in membrane preparation (i.e., the use of “strong” or “weak” nonsolvent) on structural and morphological features of polymer membranes of various chemical compositions was studied. Investigation of dilute solutions of membrane-forming polymers by optical methods revealed the changes in the state of the system both in the presence of a solvent and in the presence of a nonsolvent. On the basis of the obtained results, it was possible to estimate the sensitivity of the studied polymer/solvent/nonsolvent system to changes in the copolymer composition (a number of hydroxyl groups in the repeating unit).

The alternating copolymer of CO₂ with epoxide is a green plastic that can efficiently transform CO₂ into valuable chemicals. Despite the significant advances made, the restricted practical application of CO₂-sourced polycarbonates due to their lack of functionality has hindered field development. We successfully demonstrated the flame retardancy of poly(chloropropylene carbonate) (PCPC), a perfectly alternating copolymer of epichlorohydrin (ECH) and CO₂. This was prepared at a 200-gram scale using a high-efficacy tetranuclear organoborane catalyst. PCPC’s excellent flame-retardant performance has been proven by both the vertical combustion test (UL94 V-0) and the limiting oxygen index (LOI) value (29.1%). The underlaid flame-retardant mechanism of PCPC was clearly elucidated. As a result, we confirmed that the generated cyclic carbonates and concurrently released flame-retardant chlorine radicals, hydrogen chloride, and CO₂ during combustion render PCPC an excellent flame retardant. Furthermore, we investigated the practicability of PCPC as a halogen-rich polymeric flame retardant by blending it with commercial bisphenol A polycarbonate (BPA-PC). PCPC upgraded the flame retardancy rating of BPA polycarbonate from V-2 to V-0 even with a mere 1 wt% addition. It is our hope that this result will prove useful in future developments of advanced CO₂-sourced polymeric materials.

The demand for energy-efficient and environmental-friendly power grid construction has made the exploitation of bio-based electrical epoxy resins with excellent properties increasingly important. This work developed the bio-based electrotechnical epoxy resins based on magnolol. High-performance epoxy resin (DGEMT) with a double crosslinked points and its composites (Al₂O₃/DGEMT) were obtained taking advantages of the two bifunctional groups (allyl and phenolic hydroxyl groups) of magnolol. Benefitting from the distinctive structure of DGEMT, the Al₂O₃/DGEMT composites exhibited the advantages of intrinsically high thermal conductivity, high insulation, and low dielectric loss. The AC breakdown strength and thermal conductivity of Al₂O₃/DGEMT composites were 35.5 kV/mm and 1.19 W·m⁻¹·K⁻¹, respectively, which were 15.6% and 52.6% higher than those of petroleum-based composites (Al₂O₃/DGEBA). And its dielectric loss tanδ=0.0046 was 20.7% lower than that of Al₂O₃/DGEBA. Furthermore, the mechanical, thermal and processing properties of Al₂O₃/DGEMT are fully comparable to those of Al₂O₃/DGEBA. This work confirms the feasibility of manufacturing environmentally friendly power equipment using bio-based epoxy resins, which has excellent engineering applications.

The addition of nanoparticles serves as an effective reinforcement strategy for polymeric coatings, utilizing their unique characteristics as well as extraordinary mechanical, thermal, and electrical properties. The exceptionally high surface-to-volume ratio of nanoparticles imparts remarkable reinforcing potentials, yet it simultaneously gives rise to a prevalent tendency for nanoparticles to agglomerate into clusters within nanocomposites. The agglomeration behavior of the nanoparticles is predominantly influenced by their distinct microstructures and varied weight concentrations. This study investigated the synergistic effects of nanoparticle geometric shape and weight concentration on the dispersion characteristics of nanoparticles and the physical-mechanical performances of nano-reinforced epoxy coatings. Three carbon-based nanoparticles, nanodiamonds (NDs), carbon nanotubes (CNTs), and graphenes (GNPs), were incorporated into epoxy coatings at three weight concentrations (0.5%, 1.0%, and 2.0%). The experimental findings reveal that epoxy coatings reinforced with NDs demonstrated the most homogenous dispersion characteristics, lowest viscosity, and reduced porosity among all the nanoparticles, which could be attributed to the spherical geometry shape. Due to the superior physical properties, ND-reinforced nanocomposites displayed the highest abrasion resistance and tensile properties. Specifically, the 1.0wt% ND-reinforced nanocomposites exhibited 60%, 52%, and 97% improvements in mass lost, tensile strength, and failure strain, respectively, compared to pure epoxy. Furthermore, the representative volume element (RVE) modeling was employed to validate the experimental results, while highlighting the critical role of nanoparticle agglomeration, orientation, and the presence of voids on the mechanical properties of the nanocomposites. Nano-reinforced epoxy coatings with enhanced mechanical properties are well-suited for application in protective coatings for pipelines, industrial equipment, and automotive parts, where high wear resistance is essential.

Solid-state electrolytes are considered to be the vital part of the next-generation solid-state batteries (SSBs), due to their high safety and long operation life span. However, the two major factors that impede the expected performance of batteries are: the easy formation of lithium dendrites due to the concentration gradient of anions, and the low ionic conductivity at room temperature, which prevents reaching ideal electrochemical performance. Single-ion quasi-solid-state electrolytes (SIQSSEs) could provide higher safety and energy density, owing to absence of anion concentration gradient and solvent, as well as good lithium-ion transport ability. The porous covalent organic frameworks (COFs) are beneficial for con-structing appropriate lithium-ion transport pathway, due to the ordered 1D channel. In addition, the boroxine COFs (COF-5) offers strong ability of withdrawing anion part of lithium salt. Last but not the least, boron atom could play the role of coordinate site due to its electron deficiency. These advantages afford an opportunity to obtain a SIQSSE with high ionic conductivity and high lithium transference number (LTN) simultaneously. The COF-5 based SIQSSEs delivered a high ionic conductivity of 6.3×10⁻⁴ S·cm⁻¹, with a high LTN of 0.92 and a wide electrochemical stable window (ESW) of 4.7 V at room temperature. The LiFePO₄ (LFP)/Li cells, which was assembled with COF-5 based SIQSSE, exhibited outstanding long cycle stability, high initial capacity and favorable rate performance. The results indicated COFs could be an ideal material for single-ion solid-state electrolytes in next-generation batteries.

The constraints of traditional 3D bioprinting are overcome by 4D bioprinting integrating with adaptable materials over time, resulting in dynamic, compliant, and functional biological structures. This innovative approach to bioprinting holds great promise for tissue engineering, regenerative medicine, and advanced drug delivery systems. 4D bioprinting is a technology that allows for the extension of 3D bioprinting technology by making predesigned structures change after they are fabricated using smart materials that can alter their characteristics via stimulus, leading to transformation in healthcare, which is able to provide precise personalized effective medical treatment without any side effects. This review article concentrates on some recent developments and applications in the field of 4D bioprinting, which can pave the way for groundbreaking advancements in biomedical sciences. 4D printing is a new chapter in bioprinting that introduces dynamism and functional living biological structures. Therefore, smart materials and sophisticated printing techniques can eliminate the challenges associated with printing complex organs and tissues. However, the problems with this process are biocompatibility, immunogenicity, and scalability, which need to be addressed. Moreover, numerous obstacles have been encountered during its widespread adoption in clinical practice. Therefore, 4D bioprinting requires improvements in future material science innovations and further development in printers and manufacturing techniques to unlock its potential for better patient care and outcomes.

The demand for anisotropic aerogels with excellent comprehensive properties in cutting-edge fields such as aerospace is growing. Based on the above background, a novel heterocyclic para-aramid nanofiber/reduced graphene oxide (HPAN/rGO) composite aerogel was prepared by combining electrospinning and unidirectional freeze-drying. The anisotropic HPAN/rGO composite aerogel exhibited a honeycomb morphology in the direction perpendicular to the growth of ice crystals, and a through-well structure of directed microchannels in the direction parallel to the temperature gradient. By varying the mass ratio of HPAN/rGO, a composite aerogel with an ultra-low density of 5.34–7.81 mg·cm⁻³ and an ultra-high porosity of 98%–99% was obtained. Benefiting from the anisotropic structure, the radial and axial thermal conductivities of HPAN/rGO-3 composite aerogel were 29.37 and 44.35 mW·m⁻¹·K⁻¹, respectively. A combination of software simulation and experiments was used to analyze the effect of anisotropic structures on the thermal insulation properties of aerogels. Moreover, due to the intrinsic self-extinguishing properties of heterocyclic para-aramid and the protection of the graphene carbon layer, the composite aerogel also exhibits excellent flame retardancy properties, and its total heat release rate (THR) was only 5.8 kJ·g⁻¹, which is far superior to many reported aerogels. Therefore, ultralight anisotropic HPAN/rGO composite aerogels with excellent high-temperature thermal insulation and flame retardancy properties have broad application prospects in complex environments such as aerospace.

Due to the rapid development and potential applications of iron(III)-alginate (Fe-Alg) microgels in biomedical as well as environmental engineering, this study explores the preparation and characterization of spherical Fe-Alg microgels using droplet microfluidics combined with an external ionic crosslinking method. This study focused on the role of Fe³⁺ and examined its effects on the physical/chemical properties of microgels under different ionic conditions and reduced or oxidized states. The pH-dependent release behavior of Fe³⁺ from these microgels demonstrates their potential biomedical and environmental applications. Furthermore, the microgels can exhibit magnetism simply by utilizing in situ oxidation, which can be further used for targeted drug delivery and magnetic separation technologies.

Organisms are capable of self-growth through the integration of the nutrients provided by the external environment. This process slows down when they grow. In this study, we mimicked this self-regulated growth via a simple swelling-polymerization strategy in which the stretching polymer chains in the original networks provide entropic elasticity to restrict growth in high growth cycles. Using typical covalently crosslinked polymers, such as acrylamide-based hydrogels and HBA-based elastomers, as examples, we demonstrate that the crosslinked polymers can absorb polymerizable compounds through a swelling-polymerization process to expand their sizes, but the growth extent becomes smaller with increasing growth cycle until reaching a plateau. In addition to their size, these materials become stiffer and exhibit less swelling ability in solvents. Our work not only provides a new growing mode to tune the properties of crosslinked polymers but also discloses the underlying mechanism of crosslinked polymers in multi-cyclic swelling conditions.