Crosslinking Mechanism And Controllable Synthesis Of Self-healing Supramolecular Elastomer Based On Hydrogen Bond

Supramolecular elastomers based on hydrogen bond introduce dynamic hydrogen bonds to the crosslinking network, endowing the materials with self-healing ability and repeatability. From the perspective of crosslinking mechanism, there are two strategies to design supramolecular elastomers based on hydrogen bond: 1) the aggregationa of chain segments act as physical crosslinks; 2) forming a three-dimensional supramolecular network. In our previous work, a supramolecular elastomer with a large amount of hydrogen bonds and no phase separation was obtained, so a three-dimensional supramolecular network was formed in SESi. However, the crosslinking mechanism put forward in previous papers cannot explain the solubility of material, thus a more accurate crosslinking mechanism is needed.Herein, we prepared SESi in a simpler way, after a three-step reaction with PDMS-COOH2, UDETA, DETA and urea, the supramolecular elastomer with clearer structure was obtained. The reaction monitor with 1H-NMR, FT-IR and GPC, the measurement of the hydrogen bond strength, the viscoelastic properties test and the model reaction demonstrated a previously neglected covalent crosslink(biuret) formed, improving the mechanical strength of material, leading to a more stable hybrid network consist of hydrogen bonds and covalent bonds.Besides, we also proposed a facile way to prepare supramolecular elastomer(HSE), in which a mixture of isocyanates was used as curing agent. A series of HSE with different covalent crosslink degree was obtained, and the relationship between covalent crosslink degree and material properties was studied. The results show that the introduction of covalent crosslink stabilized the whole network, providing higher mechanical strength, restricting the movement of chains. While the hydrogen bond corsslink decides the reversibility of the whole netwrok, especially the reparable strength during self-healing process.Moreover, we proposed a method to prepare UV-curable precursor by grafting cinnamoyl group, which was used to prepare the bi-layer film(BLF), the difference in stickness caused by different covalent crosslink degree was studied. And we also took a preliminary evaluation on the application prospect of BLF as wound dressing.