Chinese Journal of Polymer Science最新文献

With the rapid development of high-power-density electronic devices, interface thermal resistance has become a critical barrier for effective heat management in high-performance electronic products. Therefore, there is an urgent demand for advanced thermal interface materials (TIMs) with high cross-plane thermal conductivity and excellent compressibility to withstand increasingly complex operating conditions. To achieve this aim, a promising strategy involves vertically arranging highly thermoconductive graphene on polymers. However, with the currently available methods, achieving a balance between low interfacial thermal resistance, bidirectional high thermal conductivity, and large-scale production is challenging. Herein, we prepared a graphene framework with continuous filler structures in in-plane and cross-plane directions by bonding corrugated graphene to planar graphene paper. The interface interaction between the graphene paper framework and polymer matrix was enhanced via surface functionalization to reduce the interface thermal resistance. The resulting three-dimensional thermal framework endows the polymer composite material with a cross-plane thermal conductivity of 14.4 W·m⁻¹·K⁻¹ and in-plane thermal conductivity of 130 W·m⁻¹·K⁻¹ when the thermal filler loading is 10.1 wt%, with a thermal conductivity enhancement per 1 wt% filler loading of 831%, outperforming various graphene structures as fillers. Given its high thermal conductivity, low contact thermal resistance, and low compressive modulus, the developed highly thermoconductive composite material demonstrates superior performance in TIM testing compared with TFLEX-700, an advanced commercial TIM, effectively solving the interfacial heat transfer issues in electronic systems. This novel filler structure framework also provides a solution for achieving a balance between efficient thermal management and ease of processing.

The preparation of high-performance thermal conductive composites containing liquid metals (LM) has attracted significant attention. However, the stable dispersion of LM within polymer solution and effective property contribution of liquid metals remains significant challenges that need to be overcome. Inspired by the properties of the dendritic structure of the tree root system in grasping the soil, “shear-induced precipitation-interfacial reset-reprotonation” processing strategy is proposed to prepare nanocomposites based on aramid micron fibers (AMFs) with hierarchical dendritic structure. Thanks to the combination of van der Waals force provided by hierarchical dendritic structure, electrostatic interaction between AMFs and LM, coordinative bonding of —NH to LM, together with interfacial re-setting and multi-step protonation, several features can be achieved through such strategy: conducive to the local filler network construction, improvement of interfacial interaction, improvement of the stability of filler dispersion in the solvent, and enhancement of mechanical and thermal properties of the films. The resulting AMFs-pH=4/LM films demonstrate a thermal conductivity of 10.98 W·m⁻¹·K⁻¹ at 70% filler content, improvement of 126.8% compared to ANFs/LM film; while maintaining a strength of ∼85.88 MPa, improvement of 77% compared to AMFs/LM film. They also possess insulation properties, enable heat dissipation for high power electronics. This work provides an effective strategy for the preparation of high performance polymer composites containing liquid metal.

Lithium-ion batteries (LIBs) benefit from an effective electrolyte system design in both terms of their safety and energy storage capability. Herein, a series of precursor membranes with high porosity were produced using electrospinning technology by mixing PVDF and triblock copolymer (PS-PEO-PS), resulting in a porous structure with good interconnections, which facilitates the absorbency of a large amount of electrolyte and further increases the ionic conductivity of gel polymer electrolytes (GPEs). It has been demonstrated that post-cross-linking of the precursor membranes increases the rigidity of the nanofibers, which allows the polymer film to be dimensionally stable up to 260 °C while maintaining superior electrochemical properties. The obtained cross-linked GPEs (CGPEs) showed high ionic conductivity up to 4.53×10⁻³ S·cm⁻¹. With the CGPE-25, the assembled Li/LiFePO₄ half cells exhibited good rate capability and maintained a capacity of 99.4% and a coulombic efficiency of 99.3% at 0.1 C. These results suggest that the combination of electrospinning technique and post-cross-linking is an effective method to construct polymer electrolytes with high thermal stability and steadily decent electrochemical performance, particularly useful for Lithium-ion battery applications that require high-temperature usage.

Poly(butylene succinate) (PBS) exhibits many advantages, such as renewability, biodegradability, and impressive thermal and mechanical properties, but is limited by the low melt viscosity and strength resulted from the linear structure. To address this, vitrimeric network was introduced to synthesize PBS vitrimers (PBSVs) based on dynamic imine bonds through melt polymerization of hydroxyl-terminated PBS with vanillin derived imine containing compound and hexamethylene diisocyanate using trimethylolpropane as a crosslinking monomer. PBSVs with different crosslinking degrees were synthesized through changing the content of the crosslinking monomer. The effect of crosslinking degree on the thermal, theological, mechanical properties, and stress relaxation behavior of the PBSVs was studied in detail. The results demonstrated that the melt viscosity, melt strength, and heat resistance were enhanced substantially without obvious depression in crystallizability, thermal stability, and mechanical properties through increasing crosslinking degree. In addition, the PBSVs exhibit thermal reprocessability with mechanical properties recovered by more than 90% even after processing for three times. Furthermore, PBSV with improved melt properties shows significantly improved foamability compared to commercial PBS. This research contributes to the advancement of polymer technology by successfully developing PBS vitrimers with improved properties, showcasing their potential applications in sustainable and biodegradable materials.

Significant progress has been made in wet adhesives for low salinity water, but exploration of general ionic adhesives for natural seawater is less developed because the high salinity could weaken interfacial bonding and shields electrostatic interactions, resulting in adhesion failure. Thus, the design of adhesives for natural seawater represents challenges less resolved. Herein, a cationic polyelectrolyte (PECHIA) containing imidazolacetonitrile unit was explored to prepare adhesives enabled by natural seawater. By combining the ion shielding effect with the “cation-dipole” interactions between PECHIA chains, aqueous solution of the PECHIA underwent coacervation and self-crosslinking in natural seawater, allowing for underwater adhesion to various substrates in seawater. The instantaneous lap-shear and tensile adhesion strengths are 47 and 119 kPa, respectively, while the cured adhesive shows ∼739 kPa tensile adhesion in natural seawater. The design of PECHIA enables wet adhesives viable for applications in the diversified scenarios of natural seawater.

The long chain branching (LCB) polyglycolide (PGA) was successfully prepared by the successive reactions of the terminal hydroxyl groups of PGA with triglycidyl isocyanurate (TGIC) and pyromellitic dianhydride (PMDA). The influence of LCB produced by functional group reaction on rheological and crystallization behavior was studied and discussed through linear rheology, uniaxial elongation and DSC (differential scanning calorimetry). The much higher viscosity and the more notable strain hardening behavior of modified PGA indicates the LCB with high degree of entanglements are created. The melt strength of PGA is finally improved greatly and can make sure that the supercritical CO₂ foaming can be carried out successfully.

The burgeoning growth of the new energy vehicles and aviation industry has escalated the need for energy storage capacitors capable of stable operation in harsh environments. The advent of metal-polyimide complexes has illuminated a novel approach for preparing temperature-resistant capacitors. However, the general application of these metal-polyimide complexes is impeded by the high dielectric loss and low breakdown strength, consequences of main-chain coordination and excessive metal ions content. Herein, our study proposes a novel polyimide-Cu complex material (POP-Cu) predicated on side-chain-type pyridine-Cu coordination, utilizing the structural backbone PMDA-ODA of mature commercial PI (Kapton) with reliable performance. Owing to the high degree of freedom afforded by the side chain with suppressed relaxation activation energy and the long-range electron delocalization formed by d-π coordination, the dielectric constant of this material containing merely 2.7 mol% Cu increases from 3.25 (POPI) to 5.58, while maintaining a remarkably low dielectric loss of 0.0066. Meanwhile, this material exhibits a substantial DC breakdown strength of 436.2 MV·m⁻¹ and a high energy density of 5.42 J·cm⁻³, coupled with superior mechanical and thermal properties. Even at 150 °C, it retains over 90% of its room-temperature energy density, demonstrating notable dielectric stability under high temperatures. These attributes underscore its promising application for capacitors operating in harsh environments.

The traditional high-temperature preparation process of polyimide can cause many problems and limits the wider application in extreme conditions. An important challenge to be solved urgently is the reduction of imidization temperature. In this work, twelve kinds of polyimide films with different chain rigidity were prepared at low temperature of 200 °C, in the absence or presence of imidazole used as the catalyst. The molecular rigidity and free volume were theoretically calculated, and relationship between structure and properties were systematically studied. The results show that imidization reaction under low temperatures is significantly affected by the rigidity of molecular chains. The rigid structure of polyimide is not conducive to the low-temperature imidization, but this adverse effect can be eliminated by adding catalyst, resulting the notably increased imidization degree. The optical and thermal properties can be improved to a certain extent for the chemically catalyzed system, resulting in relatively higher heat resistance and thermal stability. While the mechanical performance could be determined by complicating factors, greatly different from polyimide films prepared by high temperature method. To investigate aggregation structures of films, the effect of chain rigidity and catalyst on the stacking or orientation of molecular chains was further elaborated. This work can contribute to the understanding of chemically catalyzed imidization that is rarely reported in the existing research, and will provide guidance for the low-temperature preparation of high-performance polyimides.

Elastomers with high mechanical toughness can guarantee their durability during service life. Self-healing ability, as well as recyclability, can also extend the life of materials and save the consuming cost of the materials. Many efforts have been dedicated to promoting the mechanical toughness as well as the self-healing capability of elastomers at the same time, while it remains a challenge to balance the trade-off between the above properties in one system. Herein we proposed a molecular design driven by dual interactions of acylsemicarbazide hydrogen bonding and Cu²⁺-neocuproine coordination simultaneously. By introducing the reversible multiple hydrogen bonds and strong coordination bonds, we successfully fabricated an extremely tough and self-healing elastomer. The elastomer can achieve an impressive top-notch toughness of 491 MJ/m³. Furthermore, it boasted rapid elastic restorability within 10 min and outstanding crack tolerance with high fracture energy (152.6 kJ/m²). Benefiting from the combination of dynamic interactions, the material was able to self-repair under 80 °C conveniently and could be reprocessed to restore the exceptional mechanical properties.

The packaging materials with cushioning performance are used to prevent the internal contents from being damaged by the impact and vibration of external forces. The polyurethane microcellular elastomers (PUMEs) can absorb energy through cell collapse and molecular chain creep. In this study, PUMEs with different densities were investigated by scanning electron microscopy, dynamic mechanical analysis and dynamic compression tests. PUMEs exhibited significant impact resistance and the maximum peak stress attenuation ratio reached 73.33%. The protective equipment was made by PUME with the optimal density of 600 kg/m³, and then the acceleration sensing device installed with the same protective equipment fell from a height of 3, 5 and 10 m to evaluate the energy-absorbing property and reusability of PUMEs. The results showed that PUMEs equipment reduced the peak acceleration of the device by 93.84%, with a maximum deviation of 9% between actual test and simulation, and shortened the impact time of first landing by 57.39%. In addition, the equipment PUMEs equipment could effectively reduce the stress on the protected items.