Self-healing Elastomer Based On Dual Cross-links Of Metal-ligand Coordination And Hydrogen Bonding

Polymeric material may easily suffer from damage during use,and then microcracks generate inside of the materials,which are potentially dangerous and will shorten their service life.Self-healing material can heal the cracks by initiating the self-healing mechanism to prolong the using life.The self-healing systems based on dynamic covalent bonds usually require external stimuli,such as heat,light,solvent,to heal themselves with low healing efficiency.While,the self-healing systems based on dynamic non-covalent interactions usually heal themselves without external stimuli,but with low strength for the weak bonding of non-covalent bonds,which limits its practical use.Therefore,there are problems that cannot simultaneously be considered in terms of self-healing efficiency and mechanical strength about the self-healing elastomer,which are difficult to be solved by single interaction.In this thesis,we report a material designed based on a combination of dynamic metal-coordinated bond(β-diketone-europium interaction)and hydrogen bond,together in a multiphase separated network,which is able to undergo self-healing and exhibits excellent elastic property..It mainly includes two aspects as follows:(1)The dynamic coordination interaction between β-diketonate(curcumin)and europium ions was first introduced to the self-healing system.The model complexes were characterized through ESI-MS and 1H NMR to figure out the coordination structure and configuration,which possessed high coordination numbers and dynamic exchange property.The approximate binding energy of Eu(Ⅲ)-O(38.5 kcal/mol)was obtained by theoretical calculation,which was stronger than that of hydrogen bonding(5-20 kcal/mol).This work provided theoretical basis for the further self-healing research.(2)The self-healing elastomer with high efficiency and excellent mechanical property was achieved by the dual interaction of metal coordination and hydrogen bonding through introducing the curcumin coordinated with Eu3+ into the main chain of polyurethane.The structure and morphology of the polymer were characterized by 1H NMR,FT-IR,TEM and SAXS.The mechanical property of the elastomer was characterized by different tensile test,with stress at break 3.5 MPa,elongation at break 1100%(tensile rate:100mm/min),good creep resistance and fatigue resistance ability as well.The coordination interaction and hydrogen bonding were investigated to discover their contributions to the mechanical strength.It turned out that the introduction of coordination interaction and hydrogen bonding improved two orders of magnitude of the storage modulus of the material separately from the rheology test,and the crossover point between storage modulus and loss modulus obviously shifted to the low frequency therefrom.The mechanical self-healing property of the material was investigated.It showed that the healed sample of P-Cur-Eu=3:1 was enabled to achieve 98%healing efficiency after self-healing for 48 h at 25 ℃ without external stimuli.We further investigated the self-healing effect by adjusting the composition of the polymer.The results showed that the molecular weight of the soft segment and the rigidity of the hard segment greatly affected the self-healing efficiency.The P-Cur-Eu self-healing elastomers are endowed with high mechanical strength and outstanding self-healing ability,which grants the promising use in next generation wearable electronic devices,touch screens and soft robotics as the self-healing dielectric.