Synthesis And Properties Of Mechanoluminescent And Self-healable Polymeric Materials

By combining mechanoresponsive and self-healing polymeric materials,cross-linked and linear mechanochemiluminescent self-healing materials were prepared via ring opening metathesis polymerization.The mechanochemiluminescent and self-healing properties of these materials were studied.The results can be summarized as follows:1.Compared with non-cross-linked and dynamic covalent polymers,the covalently cross-linked networks are irreplaceable in many areas;however,are difficult to repair once fractured,due to the limited polymer chain diffusion after crosslinking.Herein we report a new kind of permanently cross-linked polyolefins,when attached with amide side groups,yield mechanically robust yet readily repairable materials.A key is to use low cross-linking density,which enables satisfactory elasticity and chain mobility for thermodynamically favored healing.Another key is to incorporate dense hydrogen bonds,which can serve as the sacrificial bonds and undergo reversible associations.These factors jointly promise polyolefin networks with mechanical toughness meeting the practical demands of most polyolefin based materials,as well as excellent self-healing performance(recovered spontaneously up to 96% of tensile strength).Moreover,a microscopic evaluation of how the chain entanglement proceed upon healing can be obtained by means of mechanochemiluminescence from 1,2-dioxetane as the covalent crosslinker.2.The cross-linked elastomers are difficult to be characterized and processed,also,their self-healing performances are limited on both the thermodynamic and kinetic control.Herein we report that a cyclic 1,2-dioxetane(Ad)mechanophore was successfully synthesized through ring-closing metathesis reaction(RCM)and subsquently a series of linear,mechanophore-rich and self-healing polyolefins were prepared by ring-opening metathesis polymerization(ROMP).The excellent self-healing performance of these materials results from a large number of high dynamic reversible sacrificial hydrogen bonds.Moreover,multi-mechanophore polymers(MMPs)have empowered new methodologies to evaluate self-healing efficiencies by mechanochemiluminescent intensity with unprecedented temporal and spatial resolution.