Poly­(ether imide) (PEI) is a high-performance polymer with outstanding thermal stability, mechanical strength, and processability, but a critical drawback of poor solvent resistance. Exposure to solvents including chloroform, dimethylformamide, dichloromethane, and N-methyl pyrrolidone severely compromises the mechanical and thermal performances. Herein, we report a method for preparing thermally crosslinked PEI (X-PEI) from azide-terminated PEI (N3–PEI–N3) synthesized via a one-pot diazotization–azidation reaction. X-PEI affords unprecedented solvent resistance unpossessed by conventional PEIs, as well as solution processability unrivaled by counterpart high-performance polymers such as polyimide. The glass transition temperature, storage modulus, and swelling ratio correlate positively with crosslinking density, which is determined by the molar mass and azide concentration of N3–PEI–N3. This work advances the chemistry of high-performance polymers. The method is generic and applicable to other engineering polymers.

Rising energy cost and environment-friendly awareness make energy conservation a key issue for metro operation. Reducing traction energy consumption and improving the utilisation of regenerative braking energy are two efficient solutions to conserve energy. Two optimisation models are proposed in this study for metro systems to minimise the energy consumption by exploring energy-efficient speed profile and optimum timetable. An analytical formulation through finding suitable force coefficients and driving regime-switching points is developed to investigate the optimal speed profile of a single train during its movement along complex rail tracks considering gradients, curves, tunnels and speed limits. Moreover, the synchronisation of accelerating and braking trains is much necessarily implemented when a timetable optimisation model is established for the energy-efficient operation by adjusting the dwell times, running times and turnaround times of multiple trains. A combined particle swarm optimisation and genetic algorithm are addressed to solve the model. The case studies from the actual data of a Beijing Metro line are carried out to verify the feasibility and availability of the proposed approach. Their results show that the net energy consumption of trains along the metro line is reduced by 10.99% by combining the optimal speed profiles and timetable. force coefficient of the jth non-coasting regime in section n, n≠N, 2N TR n turnaround time at terminal n (s), n = 1, N T n running time in section n (s), n≠N, 2N D n dwell time at station n (s), n≠1, N, N + 1, 2N

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The fabrication of novel poly(ionic liquids)-modified polystyrene (PSt) magnetic nanospheres (PILs-PMNPs) by a one-pot miniemulsion copolymerization reaction was achieved through an efficient microwave-assisted synthesis method. The morphology, structure, and magnetic behavior of the as-prepared magnetic materials were characterized by using transmission electron microscopy, vibrating sample magnetometry, etc. The magnetic materials were utilized as sorbents for the extraction of phthalate esters (PAEs) from beverage samples followed by high-performance ultrafast liquid chromatography analysis. Significant extraction parameters that could affect the extraction efficiencies were investigated particularly. Under optimum conditions, good linearity was obtained in the concentration range of 0.5-50 (dimethyl phthalate), 0.3-50 (diethyl phthalate), 0.2-50 (butyl benzyl phthalate), and 0.4-50 μg/L (di-n-butyl phthalate), with correlation coefficients R > 0.9989. Limits of detection were in the range 125-350 pg. The proposed method was successfully applied to determine PAEs from beverage samples with satisfactory recovery ranging from 77.8 to 102.1% and relative standard deviations ranging from 3.7 to 8.4%. Comparisons of extraction efficiency with PSt-modified MNPs as sorbents were performed. The results demonstrated that PILs-PMNPs possessed an excellent adsorption capability toward the trace PAE analytes.

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