Construction of supramolecular hydrogels using imidazolidinyl urea as hydrogen bonding reinforced factor
Jing Yu, Xingxing Chen, Yuxuan Yang, Xiaodan Zhao, Xiaojing Chen, Tianhong Jing, Yang Zhou, Jiangping Xu, Yanfeng Zhang, Yilong Cheng
Abstract
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.