Studu On Preparation And Properties Of Rare Earth Cation-? Dynamically Crosslinked Silicone Elastomers

Silicone rubber has excellent chemical stability,softness and weather resistance and is widely used in aerospace,medical and health,building materials and many other fields.Because traditional silicone rubber is often permanently cross-linked through irreversible chemical covalent bonds,the non-disassembly of the covalent network of silicone rubber materials will not only lead to a significant reduction in its service life,but also cause serious waste of resources due to its non-recyclability.Although many studies have introduced dynamic non-covalent bonds such as hydrogen bonds and metal coordination bonds into the silicone cross-linked network,which endows the silicone elastomer with self-healing ability,it fails to balance the mechanical properties and self-healing of the material.relationship between efficiency.In order to avoid the contradiction between them,based on the characteristics of"point-to-face"cross-linking area of rare earth cation-?dynamic interaction,the bond energy of the cross-linking point is high(equivalent to covalent bond),and Eu³⁺-?is designed and prepared in this paper.The presence of cation-?interaction in the polymer system was proved by experimental tests and theoretical calculations for the dynamic cross-linked silicone elastomer and silicone rubber composites.The influence of linear mechanical response behavior and self-healing performance was explored,and the recyclable experiment of composite materials was explored,which provided a new idea for the preparation of high-performance and sustainable nonlinear mechanical response advanced materials.The main research conclusions are as follows:(1)An amino-terminated silicone elastomer polymer(IN-PDMS-Eu)dynamically cross-linked by Eu³⁺-?was designed and prepared.First,the existence of Eu³⁺-?dynamic non-covalent bonds in the polymer system was proved by experimental tests and theoretical calculations such as energy dispersive spectroscopy,solid UV absorption spectroscopy,fluorescence emission spectroscopy and molecular dynamics simulation(MD);Secondly,by adjusting the crosslinking density of cation-?dynamic bonds in the system,it was determined that the mechanical properties of IN-PDMS-Eu were the best when the content of Eu³⁺was 1/4,and its elongation at break and breaking strength reached 1.04 MPa and145.5%;In addition,with the continuous increase of Eu³⁺content in the system,the degree of perfection of the dynamic cross-linking network became more and more obvious.When the Eu³⁺content was 1/4,the polymer showed obvious Payne effect and Mullins effect;Finally,based on the reversible fracture and reformation of the Eu³⁺-?dynamic cross-linked network,the silicone elastomer can achieve self-healing at 100? in only 0.5 h,and the self-healing efficiency reaches 92%.(2)A pendant amino silicone elastomer material(IN-PDMS₂-Eu)dynamically cross-linked by Eu³⁺-?was prepared.First,the structure of the polymer was determined by infrared spectroscopy(FT-IR)and solid-state carbon nuclear magnetic spectroscopy(¹³C NMR);Secondly,by adjusting the crosslinking density of Eu³⁺-?bonds in the system,it was determined that the mechanical properties of IN-PDMS₂-Eu were the best when the Eu³⁺content was 1/4,and its elongation at break and tensile strength reached 325.6%and 0.86MPa;In addition,the elastomer shows no obvious Payne effect at high cross-linking density.Compared with the aforementioned amino-terminated elastomer,the dynamic cross-linked network in the polymer is easier to break and reform;Finally,due to the influence of Eu³⁺-?interaction,when the addition amount of Eu³⁺is 1/4,the elastomer material has obvious Mullins effect,creep resistance and self-healing properties,and the Eu³⁺-?dynamic non-covalent bond Has significant energy dissipation and fast rebuilding characteristics.(3)Based on the above two polysiloxane systems,a silicone rubber composite material dynamically crosslinked by Eu³⁺-?was prepared.First,by comparing the mechanics of composites prepared based on different silicone rubber substrates,preparation methods and silica types,it was found that when the side amino silicone rubber was selected as the substrate and silica HT200 as the reinforcing filler,a simple one-pot The Eu³⁺-?dynamic cross-linked silicone rubber prepared by the method has the best and excellent mechanical properties.When the content of silica is 40 phr,the elongation at break and tensile strength reach 262.4%and 7.24 MPa;Secondly,based on the increase in the perfection of the polymer network,the composite exhibits obvious Payne effect,good creep resistance,and the creep strain is reduced from 36.5%at 10 phr to 21.5%at 40 phr;More importantly,based on the reversible breaking reformation of Eu³⁺-?dynamic crosslinks,the recovery efficiency can still reach 82.5%after hot-pressing recovery at 150?.