Preparation and Properties of Reconfigurable Elastomers with High Strength and High Toughness Crosslinked by C―N Bonds
Elastomers have indispensable applications in our daily life as they possess unique high elasticity.However,most neat elastomers are mechanically weak and they are thermosetting,which make their recycling and reuse very challengeable.Consequently,it is of great significance to develop reprocessable elastomers with high strength and high toughness.In recent years,the introduction and development of elastomers crosslinked by dynamic bonds,including the covalent ones and the noncovalent ones,have offered very good opportunities for achieving this goal.Herein,elastomers crosslinked with dual dynamic bonds,i.e.C―N bonds based on pyridium and copper ions(Cu2+)-pyridine coordination bonds,have been reported.These elastomers(VPR-BTP-Cu)were prepared by using bis(p-toluenesulfonyloxy)propane(BTP)to crosslink styrene-butadiene-vinylpyridine rubber(VPR),followed by introducing Cu2+through immersing.The structure and properties of VPR-BTP-Cu with varied Cu2+ contents were investigated using methods such as infrared spectroscopy,X-ray photoelectron spectroscopy,dynamic thermomechanical analyzer,and transmission electron microscopy.The results demonstrate that BTP can efficiently crosslink VPR,generating C―N bonds crosslinks,and the resultant VPR-BTP are reconfigurable due to the C―N transalkylation reactions at elevated temperatures.Additionally,Cu2+-pyridine coordination bonds play roles as sacrificial bonds under loading,dissipating large amount of energy and thus improving both the stiffness and toughness of the elastomers.When the Cu2+ mass fraction is 9%,the strength and toughness of VPR-BTP-Cu reach 24 MPa and 36 MJ/m3,which are 7.6 and 7.3 times of those of VPR-BTP without Cu2+,respectively.Moreover,VPR-BTP-Cu presents reconfigurable shape memory performance.This work provides a new way to fabricate reconfigurable elastomers with high performance.
elastomerC―N transalkylationsacrificial bondstrengthening and tougheningreconfigurable shape memory
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