Chinese Journal of Polymer Science最新文献

Toughening the petroleum-based epoxy resin blends with bio-based modifiers without compromising their modulus, mechanical strength, and other properties is still a big challenge in view of the sustainability. In this study, a bio-based liquid crystal epoxy resin (THMT-EP) with an s-triazine ring structure was utilized to modify a petroleum-based bisphenol A epoxy resin (E51) with 4,4′-diaminodiphenylsulfone (DDS) as a curing agent, and the blended systems were evaluated for their thermal stability, mechanical properties, and flame retardancy. The results showed that the impact strength of the blended system initially increased and then decreased with the increase in THMT-EP content, and it reached the a maximum value of 26.5 kJ/m² when the THMT-EP content was 5%, which was 31.2% higher than that of E51/DDS. Notably, the flexural strength, modulus, and glass transition temperature of the blended system were all simultaneously improved with the addition of THMT-EP. At the same time, the addition of THMT-EP enhanced the flame retardancy of the system by increasing the char yield at 700 °C and decreasing the peak heat release rate and total heat release rate. This work paves the way for a more sustainable improvement in the comprehensive performance of epoxy resin.

Janus films with asymmetric physical/chemical properties have attracted considerable attention due to their promising applications in personal thermal management, electronic skins, sensors, actuators, etc. However, traditional methods for fabricating Janus films conventionally need the assistance of an interface or auxiliary equipment, which are usually complex and time-consuming. Herein, flexible poly(vinyl alcohol) (PVA)/graphene oxide (GO)/h-BN (recorded as PVA/GO/h-BN) Janus films with thermally, optically, and electrically anisotropic properties are fabricated by a simple density deposition self-assembly method, which just utilizes the density difference between GO and h-BN during water evaporation. Experimental results show that the two sides of the acquired Janus films have obvious asymmetric characteristics. In the original state of the PVA/GO/h-BN Janus films, the thermal conductivity of the GO side (10.06 W·m⁻¹·K⁻¹) is generally lower than that of the h-BN side (10.48 W·m⁻¹·K⁻¹). But after GO is reduced, the thermal conductivity of the rGO side reaches 12.17 W·m⁻¹·K⁻¹, surpassing that of the h-BN side. In addition, the relative reflectance of the h-BN side of Janus film is also significantly higher than that of the rGO side, and the surface resistance difference between the two sides is about 4 orders of magnitude. The prepared PVA/GO/h-BN Janus films show great application potential in human thermal management, light conversion switches, and electronic skins. This study provides a simple and versatile strategy for fabricating Janus films with multifunctional (such as thermal, optical, and electrical) anisotropies.

Polyelectrolyte (PE) gels, distinguished by their unique stimuli-responsive swelling behavior, serve as the basis of broad applications, such as artificial muscles and drug delivery. In this work, we present a theoretical model to analyze the electrostatics and its contribution to the swelling behavior of PE gels in salt solutions. By minimizing the free energy of PE gels, we obtain two distinct scaling regimes for the swelling ratio at equilibrium with respect to the salt concentration. We compare our predictions for the swelling ratio with experimental measurements, which show excellent agreement. In addition, we employ a finite element method to assess the applicability range of our theoretical model and assumptions. We anticipate that our model will also provide valuable insights into drug adsorption and release, deformation of red blood cells, 4D printing and soft robotics, where the underlying mechanism of swelling remains enigmatic.

Salt-doped block copolymers have widespread applications in batteries, fuel cells, semiconductors, and various industries, where their properties crucially depend on phase separation behavior. Traditionally, investigations into salt-doped diblock copolymers have predominantly focused on microphase separation, overlooking the segregation between ionic and polymeric species. This study employs weak segregation theory to explore the interplay between phase separation dominated by the polymer-modulated mode and the salt-out-modulated mode, corresponding to microscopic and macroscopic phase separations, respectively. By comparing diblock copolymers doped with salts to those doped with neutral solvents, we elucidate the significant role of charged species in modulating phase behavior. The phase separation mode exhibits a transition between the polymer-modulated and salt-out-modulated modes at different wavenumbers. In systems doped with neutral solvents, this transition is stepwise, while in salt-ion-doped systems, it is continuous. With a sufficiently large Flory-Huggins parameter between ions and polymers, the salt-out-modulated mode becomes dominant, promoting macrophase separation. Due to the solvation effect of salt ions, salt-doped systems are more inclined to undergo microphase separation. Furthermore, we explore factors influencing the critical wavenumber of phase separation, including doping level and the Flory-Huggins parameters between two blocks and between ions and polymeric species. Our findings reveal that in a neutral solvent environment, these factors alter only the boundary between micro- and macro-phase separations, leaving the critical wavenumber unchanged in microphase separation cases. However, in a salt-doped environment, the critical wavenumber of microphase separation varies with these parameters. This provides valuable insights into the pivotal role of electrostatics in the phase separation of salt-doped block copolymers.

We present the results of molecular dynamics simulations of steady shear between a pair of neutral polymer brushes, as well as a pair of charged polymer brushes in the strongly compressed regime. The results of the molecular dynamic simulations of neutral and polyelectrolyte brushes in implicit solvent including normal forces, shear forces, viscosities and friction coefficients as a function of separation between brushes, are presented in the study. The comparison of the simulation results of neutral and charged brushes shows that the charged brushes is in the quasi-neutral regime, and the dependence of viscosity on the separation distance show the similar power law of neutral brushes. Our simulation results confirm that the implicit solvent simulations of polyelectrolyte brushes that ignore hydrodynamics interaction are in agreement with the scaling predictions qualitatively because of screening of hydrodynamic interaction and long-range electrostatic interactions on the correlation length scale. Both of neutral and charged brushes show the lubrication properties that the friction coefficient decreases with the separation decreases at enough large loads. However, a maximum of friction coefficients is observed for polyelectrolyte brushes, which is in contrast to the neutral brushes with monotonical dependence.

The evolution of high-frequency communication has accentuated the significance of controlling dielectric properties in polymer media. Traditionally, it has been theorized that rigid molecular chains lead to lower dielectric loss. However, the validity of this proposition at high frequencies remains uncertain. To scrutinize the correlation between chain flexibility and dielectric properties, we synthesized six poly(ester imide)s (PEIs) with systematically varied molecular chain flexibilities by modifying the ester’s substitution on the aromatic ring. The introduction of ester bonds bestowed all PEI films with a low dielectric dissipation factor (D_f), ranging from 0.0021 to 0.0038 at 10 GHz in dry conditions. The dry D_f displayed a pattern consistent with volume polarizability (P/V). Unexpectedly, PI-mmm-T, featuring the most flexible molecular chain, exhibited the lowest dielectric loss under both dry (0.0021 @ 10 GHz) and hygroscopic (0.0029 @ 10 GHz) conditions. Furthermore, the observed increase in D_f after humidity absorption suggests that the high dielectric loss of PEI in applications may be attributed to its hygroscopic nature. Molecular simulations and characterization of the aggregation structure revealed that the smaller cavities within flexible molecular chains, after close stacking, impede the entry of water molecules. Despite sacrificing high-temperature resistance, the precursor exhibited enhanced solubility properties and could be processed into high-quality films. Our research unveils new insights into the relationship between flexibility and high-frequency dielectric loss, offering innovative perspectives on synthesizing aromatic polymers with exceptional dielectric properties.

Olefin polymerization is one of the most important chemical reactions in industry. This work presents a strategy that emphasizes the synergistic meta/para-steric hindrance of N-aryl groups and electronic effects in newly synthesized neutral salicylaldiminato nickel catalysts. These nickel(II) catalysts exhibit exceptional thermostability, ranging from 30 °C to 130 °C, demonstrating enhanced catalytic activities and broadly regulated polyethylene molecular weights (3–341 kg·mol⁻¹) and controlled polymer branch density (2–102 brs/1000C). The preferred catalyst Ni3 with concerted steric and electronic effects enables the production of solid-state semi-crystalline polyethylene materials at temperatures below 90 °C. Notably, Ni3 exhibits an impressive tolerance of 110 °C and can withstand even the challenging polymerization temperature of 130 °C, leading to the production of polyethylene wax and oil. Also, functionalized polyethylene is produced.

Polyelectrolyte solutions are more variable than uncharged macromolecule due to electrical interaction between charged molecules and surrounding counterions. Therefore, the subject of polyelectrolyte solutions has attracted a wide range of interests in both basic and applied research, and has also been extensively explored. However, the understanding of the molecular dynamics and conformation of polyelectrolytes in solution remains to be deepened, and universal consensus on some key issues have not been reached. Many methods have contributed to solving the above problems in different ways, including dielectric relaxation spectroscopy (DRS). In this perspective, we briefly reviewed the history of dielectric spectroscopic research on polyelectrolyte solution, with emphasis on summarizing our efforts. In particular, we expound the characteristics of DRS and its ability to obtain the internal information of the system of interest. Finally, we evaluate the advantages and limitations of the dielectric method and discussed future prospects of this field.

Plasma treatment is necessary to optimize the performance of biomaterial surfaces. It enhances and regulates the performance of biomaterial surfaces, creating an effective interface with the human body. Plasma treatments have the ability to modify the chemical composition and physical structure of a surface while leaving its properties unaffected. They possess the ability to modify material surfaces, eliminate contaminants, conduct investigations on cancer therapy, and facilitate wound healing. The subject of study in question involves the integration of plasma science and technology with biology and medicine. Using a helium plasma jet source, applying up to 18 kV, with an average power of 10 W, polymer foils were treated for 60 s. Plasma treatment has the ability to alter the chemical composition and physical structure of a surface while maintaining its quality. This investigation involved the application of helium plasma at atmospheric pressure to polyamide 6 and polyethylene terephthalate sheets. The inquiry involves monitoring and assessing the plasma source and polymer materials, as well as analyzing the impacts of plasma therapy. Calculating the mean power of the discharge aids in assessing the economic efficacy of the plasma source. Electric discharge in helium at atmospheric pressure has beneficial effects in technology, where it increases the surface free energy of polymer materials. In biomedicine, it is used to investigate cytotoxicity and cell survival, particularly in direct blood exposure situations that can expedite coagulation. Comprehending the specific parameters that influence the plasma source in the desired manner for the intended application is of utmost importance.

The thermochromic mechanism and the structure-property regulation principle of reversible thermochromic polydiacetylene (PDA) materials have always been a challenging issue. In this work, a series of diacetylene monomers (m-PCDA) containing phenyl and amide or carboxyl groups were synthesized from 10,12-pentacosadiynoic acid (PCDA) through the esterification or amidation reactions. The effects of the number and the distribution of the functional groups in m-PCDA molecules on their solid-state polymerization capability, and the thermochromic mechanism of their corresponding polymers (m-PDA) were investigated and discussed in detail. The results show that the m-PCDA monomers containing both benzene ring and groups that can form hydrogen bonding interactions have strong intermolecular interaction, and are easy to carry out the solid phase polymerization under 254-nm UV irradiation to obtain the corresponding new thermochromic m-PDA materials. The thermochromic behavior of m-PDA depends on its melting process. The initial color-change temperature (blue to red) is determined by the onset melting temperature, and the temperature range in which reversible color recovery can be achieved by repeat heating-cooling treatment is determined by its melting range. According to the proposed thermochromic mechanism of PDA, various new PDA materials with precise thermochromic temperatures and reversible thermochromic temperature ranges can be designed and synthesized through the appropriate introduction of benzene ring and groups that can form hydrogen bonding interactions into the molecular structure of linear diacetylene monomer. This work provides a perspective to the precise molecular structure design and the property regulation of the reversible thermochromic PDA materials.