Department of Applied Chemistry, School of Science, MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter (Xi'an Jiaotong University) and State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China.
J Mater Chem B. 2020 Apr 21;8(15):3058-3063. doi: 10.1039/d0tb00331j. Epub 2020 Mar 23.
The development of a new hydrogen bonding reinforced factor is of importance for the design and application of supramolecular hydrogels. Herein, we use a new reinforced factor, imidazolidinyl urea (IU), for the construction of hydrogen bonding supramolecular hydrogels. Poly(ethylene glycol) (PEG), three types of diisocyanates (isophorone diisocyanate (IPDI), 4,4'-methylene bis(cyclohexyl isocyanate) (HMDI) and 4,4'-methylene bis(phenyl isocyanate) (MDI)) and IU were employed to synthesize a series of polymers through hydroxyl-isocyanate chemistry. We found that increased IU content and hydrophobicity of the diisocyanates led to a higher gel-sol transition temperature of the polymer aqueous solutions, and the formed hydrogel showed great self-healing capability in response to external mechanical forces. Moreover, we found that improved diisocyanate hydrophobicity could endow the hydrogel with promising mechanical strength, with 1.6 MPa tensile stress and 460% elongation at the break. The advanced hydrogel can also efficiently dissipate energy during deformation and can quickly recover from 200% strain at room temperature without any assistance. Since IU is commercially available and ready for polymer preparation, our work provides a simple and convenient method for the development of hydrogen bonding supramolecular hydrogels with advanced properties.
新型氢键增强因子的开发对于超分子水凝胶的设计和应用具有重要意义。本文采用新型增强因子咪唑烷脲（IU）构建氢键超分子水凝胶。通过羟基-异氰酸酯化学，我们使用聚乙二醇（PEG）、三种二异氰酸酯（异佛尔酮二异氰酸酯（IPDI）、4,4'-亚甲基双（环己基异氰酸酯）（HMDI）和 4,4'-亚甲基双（苯基异氰酸酯）（MDI））和 IU 合成了一系列聚合物。我们发现，IU 含量的增加和二异氰酸酯疏水性的增加导致聚合物水溶液的凝胶-溶胶转变温度升高，所形成的水凝胶对外力具有很强的自修复能力。此外，我们发现提高二异氰酸酯疏水性可以赋予水凝胶优异的机械强度，其拉伸应力可达 1.6 MPa，断裂伸长率可达 460%。这种先进的水凝胶在变形过程中还可以有效地耗散能量，并且可以在室温下无需任何辅助即可从 200%的应变快速恢复。由于 IU 可商购且可用于聚合物制备，因此我们的工作为开发具有先进性能的氢键超分子水凝胶提供了一种简单便捷的方法。
