Synthesis And Characterization Of Supramolecular Elastomers Based On Metal-ligand Interaction And Ionic Hydrogen Bond

The incorporation of reversible crosslinks into polymer matrix can endow the polymer with some special properties,such as reprocessing,self-healing,stimuli-responding,etc.In our previous work,a novel elastic cross-linking network?Al-GCS?was constructed by using the coordination between the aluminum ions and carboxyl.However,due to the strong and stable Al?III?-carboxylate coordination,the self-healing properties of the network is poor.In this work,based on the Al-GCS coordination structure,we utilize a simple metal-ligand coordination between amino group?-NH₂?and Al?III?to prepare a self-healable polydimethylsiloxane elastomer?PDMS-NH₂-Al-x?.The N atom of the primary amine has lone pair electron that can provide to the empty orbit of Al?III?,which can forming a weak and unstable coordination bond,thus endow the network with excellent self-healing properties even at-20°C.The synthetic route of amino-grafted polydimethylsiloxanes?PDMS-NH₂?has been changed to obtain a controlled molecular weight and amine value contrary with the traditional bulk polymerization.The Al?III?can coordinate with six N atoms to form a six coordinate structure in solid state,which was proved by FT-IR,¹³C-NMR and ²⁷Al-NMR.The effects of different NH₂/Al?III?on the mechanical properties,viscoelastic properties and self-healing behavior of the materials were investigated.The results show that the properties of the network can be controlled by the ratio of NH₂/Al?III?.Besides,according to the proton transfer between carboxyl?-COOH?and amine?-NH₂?,we proposed a method to prepare a self-healing elastermer?PDMS-NH₂-C-x?based on ionic hydrogen bond,using commercially available and renewable chemical citric acid as non-covalent crosslinker.The effects of different COOH/NH₂ on the mechanical properties,viscoelastic properties and self-healing behavior of the materials were investigated.The results show that the PDMS-NH₂-C-x are amorphous crosslinked elastomer at ambient conditions,and ionic hydrogen bond can be dissociated with the increasing of temperature.The excess of carboxyl result in a stable and a strong network,but reduces its self-healing properties.Moreover,the PDMS-NH₂-C-x shows excellent reprocessing properties.