Masking Strategy Constructed Metal Coordination Hydrogels with Improved Mechanical Properties for Flexible Electronic
Xiaoyu Guan1,2,3, Sai Zheng1, Bingyuan Zhang1
1College of Bioresources Chemical and Materials Engineering, Key Laboratory of Auxiliary Chemistry and Technology for Chemical Industry, Ministry of Education, Shaanxi Collaborative Innovation Center of Industrial Auxiliary Chemistry and Technology, College of Mechanical and Electrical Engineering, Shaanxi University of Science & Technology, Xi'an, Shaanxi 710021, China.
Abstract:
Metal coordination hydrogels (MC-HGs) that introduce dynamically coordinate bonds together with metal ionic conduction have attracted considerable attention in flexible electronics. However, the traditional soaking method alleged to have technical scalability faces the challenge of forming MC-HGs with a "core-shell" structure, which undoubtedly reduces the whole mechanical properties and ionic stimulation responsiveness required for flexible electronics materials. Herein, a novel strategy referred to as "masking" has been proposed based on the theory of the valence bond and coordination chemistry. By regulating the masking agents and their concentrations as well as pairing mode with the metal ions, the whole mechanical properties of the resulting composites (MC-HGs) show nearly double the values of their traditional soaking samples (MC-HGs). For example, the fracture stress and toughness of Fe-HGs are 1.55 MPa and 2.14 MJ/m3, almost twice those of Fe-HGs (0.83 MPa and 0.93 MJ/m3, respectively). Microstructure characterization combined with finite element analysis, molecular dynamics, and first-principles simulations demonstrates that the masking strategy first facilitating interfacial permeation of metal complexes and then effective coordination with functional ligands (carboxylates) of the hydrogels is the mechanism to strengthen the mechanical properties of composites MC-HGs, which has the potential to break through the limitations of current MC-HGs in flexible electronic sensor applications.
