Preparation And Application Of Tough And Self-healing Polysiloxane Elastomer

Polysiloxane elastomers with good thermal stability and biocompatibility are widely used in flexible electronic devices and wearable devices.However,due to folding or scratches,cracks will occur during the use of elastomers,which will affect its service life and safety.Herein,we propose a new design strategy by creating a double physical crosslinking network that contains at least three competitive interactions to achieve a tough and body-temperature self-healing elastomer.First,a urea-containing PDMS（PDMS-U）was synthesized through a chain extending reaction between bis（3-aminopropyl）-terminated poly（dimethylsiloxane）（H₂N-PDMS-NH₂）and 2,4-tolylene diisocyanate（TDI）.The introduction of urea groups was designed to offer hydrogen bonding and urea/metal ion coordination interactions.Second,a carboxylic acid（-COOH）functionalized PDMS（PDMS-C）was synthesized via post-modification of the vinyl containing PDMS precursor.The introduction of-COOH was aimed at forming COO^-/metal ion coordination bonds.Finally,mixing PDMS-U and PMDS-C with different metal ions could create PDMS elastomers with a dual network arising from three competitive interactions,i.e.,hydrogen bonding of ureas,and urea/metal ion and COO^-/metal ion coordination interactions.¹H NMR,GPC,UV-vis,and tensile tests were applied to characterize the molecular structures,metal coordination and mechanical properties of elastomers.The mechanical strength of polysiloxane elastomers after metal ion coordination has been improved significantly.（1）The PDMS-U/PDMS-C_0.3/Zn²⁺composite by Zn²⁺coordination shows the best comprehensive properties with tensile strength,breaking strain and toughness up to 4.0 MPa,776%,and 16.0 MJ/m³,respectively.This composite film has a great application on wearable devices.（2）The PDMS-U/PDMS-C_0.3/Cu²⁺composite by Cu²⁺coordination shows the best comprehensive properties with tensile strength,breaking strain,and toughness up to 4.4 MPa,588%,and 16.1 MJ/m³,respectively.The robust self-healing elastomer can be used as a flexible substrate to easily fabricate healable electrodes.（3）The PDMS-U/PDMS-C_0.5/Eu_2.0³⁺ composite by Eu³⁺coordination shows the best comprehensive properties with tensile strength,breaking strain,and toughness up to 2.4 MPa,643%,and 8.8 MJ/m³,respectively.And this PDMS-U/PDMS-C_0.5/Eu_2.0³⁺ composite film shows fluorescence performance.In summary,we prepare the tough and self-healing polysiloxane elastomer with the metal ion reinforced dual network structure.The effect of different valence metal ions on the mechanical properties of elastomers was investigated.The design of metal ion reinforced dual network structure can not only give good mechanical and self-healing properties to elastomers,but also broaden their application range.