Jiasheng Qian

The high-performance electronic equipment appearing in the information age puts forward more comprehensive requirements for polymer-based composites with high heat dissipation capability, good mechanical properties, and substantial fire safety performance. However, the low interfacial interaction caused by the phase structural difference between the fillers greatly reduced the improvement of performance of the composites. It is feasible to overcome this issue by forming chemical interaction to regulate the interface structure. Herein, an anisotropic oriented composite is obtained by layer-by-layer self-assembly stacking of one-dimensional aramid nanofibers (ANFs) and ionic liquid (IL) functionalized two-dimensional boron nitride nanosheets (BNNSs). Considering the influence of the interface structure on the performance, the IL containing imidazolium ring and hexadecyl selected by density functional theory (DFT) form effective interface interactions with BNNSs. Owing to the establishment of multiple non-covalent bonding (cation–π, and CH–π) interactions, the composite exhibits not only high thermal conductivity (15.2 W m⁻¹ K⁻¹) and tensile strength (63.2 MPa) but also has excellent flame-retardant properties (limited oxygen index ≈ 45). Such an outstanding performance results in effectively cool light-emitting diode modules and desktop computers, outperforming a commercial thermal gasket. Significantly, molecular dynamics (MD) and DFT simulations further elucidate the role of IL in promoting heat transfer and the thermal conductivity mechanism between BNNS interfaces, respectively. This study offers a feasible strategy for constructing an interfacial structure by screening the modifier molecular configuration to perfect the excellent versatility of thermal management composites.

Poly(vinylidene fluoride) was grafted with maleic anhydride through reactive extrusion by using diisopropyl benzene peroxide as an initiator and 9-vinyl anthracene as a stabilizer. Effects of various parameters on grafting degree were investigated including the amounts of monomer, initiator and stabilizer. The maximum extent of grafting achieved was 0.74%. The graft polymers were characterized using FTIR, water contact angle, thermal, mechanical and XRD studies. Improved hydrophilic and mechanical properties were observed for graft polymers.

聚乙烯(Polyethylene,PE)作为应用最为广泛的聚合物材料，具有优良的力学和加工性能。为了研究聚乙烯材料的导热性能，构建了结晶聚乙烯的粗粒化模型，利用分子动力学模拟研究方法探索了结晶对聚乙烯本征导热性能的影响。首先，利用玻尔兹曼反演法和实验数据优化相结合的方法，建立了研究结晶聚乙烯导热性能的粗粒化模型。为了验证了体系参数的正确性，通过测试粗粒化模型体系的玻璃化转变温度、热膨胀系数、均方回转半径、扩散系数以及导热系数等物性数据与实验和文献报道的数据进行比对分析。利用建立的结晶聚乙烯模型，研究了在拉伸形变过程中，结晶度和晶粒尺寸对聚乙烯结晶体系导热性能的影响—高结晶度的体系更容易被拉伸取向形成高导热体系。在相同结晶度下，球晶尺寸越大的体系，越容易形成高导热体系。模拟结果对于研究结晶高分子体系的本征导热性能具有重要的参考价值。

Every metal and metallurgical industry is associated with the generation of wastewater, influencing the living and non-living environment, which is alarming to environmentalists. The strict regulations about the dismissal of acid and metal into the environment and the increasing emphasis on the recycling/reuse of these effluents after proper remedy have focused the research community’s curiosity in developing distinctive approaches for the recovery of acid and metals from industrial wastewaters. This study reports the synthesis of UiO-66-(COOH)₂ using dual ligand in water as a green solvent. Then, the prepared MOF nanoparticles were introduced into the DMAM quaternized QPPO matrix through a straightforward blending approach. Four defect-free UiO-66-(COOH)₂/QPPO MMMs were prepared with four different MOF structures. The BET characterization of UiO-66-(COOH)₂ nanoparticles with a highly crystalline structure and sub-nanometer pore size (~7 Å) was confirmed by XRD. Because of the introduction of MOF nanoparticles with an electrostatic interaction and pore size screening effect, a separation coefficient (S_HCl/FeCl2) of 565 and U_HCl of 0.0089 m·h⁻¹ for U-C(60)/QPPO were perceived when the loading dosage of the MOF content was 10 wt%. The obtained results showed that the prepared defect-free MOF membrane has broad prospects in acid recovery applications.

Polymer-based thermal conductive composites are essential to alleviating heat accumulation in electronic equipment. However, non-neglectable interface thermal resistance between fillers is unfavorable to their thermal conductivity, thus invalidating their applicability to electronic components. In this work, a low thermal resistance interface structure in adjacent graphene was constructed by functionalization of cationic poly(3-hexylthiophene) (C-P3HT) on an exfoliated graphene (E-G) surface. A “dual channel” for heat transfer between graphene layers was created through cation–π and π–π interactions between quaternary ammonium and the thiophene ring in both C-P3HT and E-G. The “dual channel” structures are assisted by C-P3HT with intrinsic thermal conductivity to form a continuous in-plane heat transfer pathway in composites. The advantage of E-G@C-P3HT/PVA results in a very high in-plane thermal conductivity up to 11.1 W m⁻¹ K⁻¹ along with good mechanical properties. The enhanced heat transfer effect of “dual channel” structures was further verified by molecular dynamics simulation analysis of phonon transport behavior at the interface of C-P3HT modified E-G. This study provides a new way to improve the thermal conductivity of composites by effectively reducing the interface thermal resistance.

With a trend of continuing improvement in the development of electronic devices, a problem of serious heat accumulation has emerged which has created the need for more efficient thermal management. Graphene sheets (GNS) have drawn much attention with regard to heat transfer because of their excellent in-plane thermal conductivity; however, the ultrahigh interfacial thermal resistance between graphene lamellae has seriously restricted its practical applications. Herein, we describe heat transfer membranes composed of graphene which have been modified by intrinsic thermally conductive polymers with different molecular weights. The presence of macromolecular surface modifiers not only constructed the graphene heat transfer interface by π–π interactions, but also significantly enhanced the membranes’ in-plane thermal conductivity by utilizing their intrinsic heat transfer properties. Such results indicated that the in-plane thermal conductivity of the fabricated membrane exhibits a high in-plane thermal conductivity of 4.17 W m⁻¹ K⁻¹, which, containing the GNS modified with 6000 g/mol (M_n) of poly(3-hexylthiophene) (P3HT), was 26 times higher that of poly (vinylidene fluoride) (PVDF). The P3HT molecular chain with specific molecular weight can form more matching structure π–π interactions, which promotes thermal conductivity. The investigation of different molecular weights has provided a new pathway for designing effective interfacial structures to relieve interface thermal resistance in thermally conductive membranes.

Polyolefin-based anion exchange membranes have recently been increasingly studied, but obtaining polyolefins with controllable molecular weights and high chemical stability under facile and metal-free conditions remains a critical challenge. Here, we demonstrate a novel strategy of exploiting visible light-induced reversible addition–fragmentation chain transfer polymerization (Vis-RAFT) for the preparation of poly(2-chloroethyl vinyl ether) (PCEVE), which exhibits high alkaline stability. With this strategy, we can control the molecular weight of PCEVE by an “on/off” light procedure. The quaternization of PCEVE yields quaternized poly(2-chloroethyl vinyl ether) (PQEVE) membranes with a well-defined microphase-separated morphology, a high chloride conductivity of 26.1 mS cm⁻¹ at 30 °C, and a significantly reduced water swelling of 1.2% at 80 °C. We anticipate that this strategy can be a potent alternative to metal-catalysed coordination polymerization or metathesis polymerization in preparing high molecular weight polyolefins for membrane applications.

In this work, a series of bimodal polymethyl methacrylate (BPMMA) was fabricated via solution-blending two neat PMMA resins. Rheology, DMTA, thermal infrared imager measurements were used in an attempt to probe the internal structure of the as-prepared BPMMA. It was demonstrated that the thermorheological behavior of the BPMMA was heavily dependent on shear rate, temperature as well as blending ratio. In addition, a typical “V-shaped” response, namely, a dip in storage modulus (G′) followed by an upturn in the plot of G′ versus measuring temperature for D4 (with lower weight-average molecular weight) was observed, characteristic of occurrence of thermorheological complexity. Our experimental results of physical–mechanical testings suggested that the BPMMA had better comprehensive properties than those of their neat PMMA counterparts.