聚脲的绿色合成、性能及应用

Green Synthesis, Properties and Applications of Polyurea

聚脲是一类性能优异的高分子材料,具有良好的热稳定性和耐腐蚀性能。聚脲的传统制备方法通常以异氰酸酯为原料,其毒性大且易与水发生副反应。因此,聚脲的绿色合成方法及性能多样的聚脲材料的合成,具有重要的研究意义和潜在应用价值。本文主要综述了聚脲的绿色合成方法,包括直接或间接使用CO2方法合成聚脲的研究进展。从催化剂、二胺分子结构和分子量等角度探讨了对聚脲分子量、热学、力学性能等方面的影响,并且归纳了功能性二氧化碳基聚脲如热塑性聚脲塑料、聚脲弹性体的性能和应用。最后对聚脲材料未来的研究重点和发展趋势进行了阐述。

Polyurea is a kind of high performance polymer materials, due to their thermal stability and chemical resistance.However, polyurea is usually prepared from isocyanate, which is toxic and easy to react with water. Therefore, studies on the green synthesis strategy of polyurea and the development of polyurea with various performances are very important for potential utilizations. Herein, the green synthesis methods of polyurea are reviewed, including directly or indirectly using CO2 as carbonyl block:(1) Polyurea can be prepared by direct polycondensation of CO2 and diamine. Catalyst can accelerate the reaction process and shift the balance to the right. It is easy to remove water, thereby improve the molecular weight and properties of polyurea by secondary polycondensation.(2) CO2 can react with methanol, phenol, ethylene oxide and propylene oxide to form dimethyl carbonate, diphenyl carbonate and cyclic carbonate. These carbonates can react with diamine compounds to form carbamates. Then, polyurea can be prepared by self-condensation of carbamate or by transurethane reaction of carbamate with diamine. High molecular weight polyurea can be obtained by the removal of methanol, phenol and so on under mild conditions.(3) CO2 can react with NH3 to form urea, and then polyurea is prepared by the condensation reaction of urea and diamine. The produced NH3 in the reaction process could be easily removed, leading to high molecular weight polyurea. The influence of catalysts, chemical structure and molecular weight of diamines on the properties of polyurea like molecular weight, thermal stabilities and mechanical properties are discussed. In addition, the properties and possible applications of CO2 based functional polyureas such as thermoplastic polyurea plastics and elastomers are summarized. Finally, the emphasis of future researches and the vast potential for the development of polyurea materials are prospected.