How do hyperbranched polyimides form in polymerizations of N,N’-bismaleimide-4,4′-diphenylmethane with barbituric acid?

Improved thermal and mechanical properties of bismaleimide nanocomposites via incorporation of a new allylated siloxane graphene oxide

A thermosetting resin system based on bismaleimide (BMI) has been developed via copolymerization with 4,4′-diaminodiphenylsulfone in the presence of a newly synthesized graphene oxide, modified using allylated siloxane (AS-GO). The curing behavior of the AS-GO-containing resin system was evaluated using curing kinetics. The dispersibility of AS-GO in the resin was observed through polarizing optical microscopy (POM), which indicates that AS-GO has good dispersibility in the resin due to GO modified with allylated siloxane which has a good phase compatibility with BMI. The effect of AS-GO on the thermomechanical and mechanical properties of the cured modified resin was also studied. Results of thermogravimetric analysis indicated that the cured sample systems display a high char yield at lower concentrations of AS-GO (≤0.5 wt%) with an improved thermal stability. Using dynamic mechanical analysis, a marked increase in glass transition temperature (T_g) with increasing AS-GO content was observed. Mechanical property analyses revealed a possible effect of AS-GO as a toughener, and the results showed that an addition of 0.3% AS-GO maximized the toughness of the modified resin systems, which was confirmed by analysis of fracture surfaces.

A thermosetting resin system based on bismaleimide has been developed via copolymerization of a new allylated siloxane graphene oxide.

Interface Interaction Behavior of Self-Terminated Oligomer Electrode Additives for a Ni-Rich Layer Cathode in Lithium-Ion Batteries: Voltage and Temperature Effects

Self-terminated oligomer additives synthesized from bismaleimide and barbituric acid derivatives improve the safety and performance of lithium-ion batteries (LIBs). This study investigates the interface interaction of these additives and the cathode material. Two additives were synthesized by Michael addition (additive A) and aza-Michael addition (additive B). The electrochemical performances of bare and modified LiNi_0.6Mn_0.2Co_0.2O₂ (NMC622) materials are studied. The cycling stability and rate capability of NMC622 considerably improve on surface modification with additive B. According to the differential scanning calorimetry results, the exothermic heat of fully deliathiated NMC622 is dramatically decreased through surface modification with both additives. The electrode surface kinetics and interface interaction phenomena of the additives are determined through surface plasma resonance measurements in operando gas chromatography-mass spectroscopy (GCMS) and in situ soft X-ray absorption spectroscopy (XAS). The binding rate constant of additive B onto NMC622 particles is 1.2-2.3 × 10⁴ M^-1 s^-1 in the temperature range of 299-311 K, which is ascribed to the strong binding affinity toward the electrode surface. This affinity enhances Li⁺ diffusion, which allows the electrode modified by additive B to provide high electrochemical performance with superior thermal stability. In operando GCMS reveals that gas evolution due to the electrolyte degradation at the NMC622 surface contributes to safety hazards in the bare NMC622 material. In situ soft XAS indicates the occurrence of structural transformation in the bare NMC622 material after it is fully charged and at elevated temperatures. The NMC622 material is stabilized by incorporating additives. The unique performance of additive B can be attributed to its linear structure that allows superior electrode surface adhesion compared with that of additive A. Therefore, this study presents an optimized working principle of self-terminated oligomers, which can be developed and applied to improve the safety and performance of LIBs.