In recent years, gel materials have attracted great attention from researchers in various fields because of their flexible and adjustable mechanical properties and rich functions. However, gel materials often have low stability due to solvent migration, and are prone to swelling or drying deformation, which has become a bottleneck problem restricting the in-depth application of gel materials. Although several strategies have been developed to improve the stability of the gel, however, from a thermodynamic point of view, if the amount of solvent in the gel deviates from the equilibrium swelling state of the polymer, the solvent will inevitably migrate. Therefore, to accurately control the solvent content in the gel and maintain high stability, it is necessary to effectively inhibit the kinetic process of solvent migration.
Idea of organic gel construction based on “molecular blocking” supramolecular mechanism. (Photo courtesy of the research group)
Mechanical interlocking action connects different molecules through geometric relationships in the molecular structure, which allows non-covalently linked molecules to maintain a stable aggregation state. Associate Professor Wu Youshen and Professor Zhang Yanfeng of the “Intelligent Polymer” team of the School of Chemistry of Xi’an Jiaotong University drew inspiration from the principle of mechanical interlocking supramolecular and proposed the “molecular blocking” supramolecular mechanism, which effectively inhibits the migration of solvents in the gel by using the blockage caused by the size difference between solvent molecules and cross-networked structures.
By designing and synthesizing liquid branched citrate ester (BCE) with a molecular size of more than 1.4 nm, and using this large volume molecule as a solvent to polymerize with crosslinked polyurea in situ, a series of novel “molecular blocking” gels were prepared. “Molecularly blocked” gels offer excellent stability comparable to common polymers or elastomers, can be stored for up to 10 months without any morphological or mechanical changes, and can withstand high-temperature baking to maintain stable quality and performance. In particular, the Young’s modulus of “molecular blocking” gels can be continuously regulated over a wide range of 1.3 GPa to 30 kPa with a record 43,000-fold change, effectively covering the range of existing crosslinking resins, plastics, elastomers and gels.
At the same time, the “molecular blocking” effect, as a non-covalent dissipation mechanism, gives the gel material unique viscoelastic mechanical properties, making it highly damped, reaching and surpassing commercial polyurethane and polyurea materials.
The above research results were recently published in Advanced Materials, with the School of Chemistry of Xi’an Jiaotong University as the first unit and the School of Life Sciences of Xi’an Jiaotong University as the cooperative unit. The first author of the paper is Associate Professor Wu Youshen of the School of Chemistry, and the corresponding author of the paper is Professor Zhang Yanfeng, Deputy Dean of the School of Chemistry. This research was supported by the National Natural Science Foundation of China and the Analysis and Testing Center of Xi’an Jiaotong University. (Source: Yan Tao, China Science News)
Related paper information:https://onlinelibrary.wiley.com/doi/10.1002/adma.202306882
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