The Synthesis Of Maleimide Derivatives Using An Acidic Ionic Liquid As A Catalyst

Maleimides are the kind of important fine chemicals, and have been widely used in industry. Among them, N-arylmaleimides are mostly used as crosslinking agents for’ natural fiber and modifiers for the engineering plastics. The modified resins showed excellent heat resistance and processability, so they have been applied for the modification of ABS, PP, PVC, PMMA and etc. In addition, maleimides have been used as the anti-bacterial agents in the ship and sewer for their antibacterial activity, which can prevent the pest’s multiplication on the equipment and do no harm to other creatures and the seawater. Bismaleimides contain unsaturated end groups which can polymerize without volatiles. The homopolymerization and copolymerization of bismaleimide gave the resins exhibiting good heat-resistant and electric insulating property. They have been utilized for the production of multilayer printed wiring boards for large-scale computers and fiber-reinforced plastics for aerospace industry. Accordingly, developing a convenient route for the preparation of maleimide derivatives is very desirableThe object of this article is to solve the problem which existed in the N-benylmaleimide industry such as water pollution, complicated process, and the high cost. We successfully developed a method to synthesis the N-benylmaleimide conveniently and economically based on researching the synthesis method of N-benylmaleimide. Then, we optimized the synthesis condition and applied this method to synthesis other N-substituted maleimides. What’s more, we designed a new kind of fluorinated bismaleimide and studied its curing property.Firstly, we used the acid ionic liquid as catalyst to synthesis the N-benylmaleimide from N-benylmaleamic acids, and the N-phenylmaleimide was obtained in a yield of near80%with a purity of98%. We optimized the reaction conditions through discussing the influence of the solvents, catalyst, reaction temperature, and the reaction time. The result showed that the highest yield was obtained when the molar ratio of N-phenylmaleamic acid to the ionic liquid was3:1and the reaction time was3h. The products were obtained through merely a decanting and removal of the solvent, suggesting that this procedure is superior to the conventional routes. By using the above optimized synthetic route, we further investigated the generality of the substrates. The bismaleimide and the substituted monomaleimides were obtained with high purity and isolated yields of higher than50%, exhibiting that the acidic ionic liquid is suitable for a wide range of substrates. A series of recycle experiments were carried out with taking N-phenyhnaleimide as an example in order to evaluate the reusability of ionic liquid, and the results showed that ionic liquid has high catalysis activity after being reused for seven times, suggesting that the ionic liquid procedure is much superior to the conventional routes.At last, we designed and synthesized a new kind of fluorinated bismaleimide using the method we developed. This new bismaleimide has a low melting point of132℃, which is20℃lower than that of MDA-BMI, and it has much wider processing windows than that of MDA-BMI.