Experimental And Computational Simulation Study On The Design And Preparation Of Elastomers With Self-Healing And Structural Color Based On Dynamic Bonds

The elastomers inevitably suffer from scratches and damage during the practical application,thus design and fabrication of self-healing elastomers with covalent adaptive networks is a effective strategy to extend the service life of materials.In addition,in order to make elastomers with not only self-healing properties but also bright structural colors,the extensive use of conventional coloring agents can be harmful to the environment as well as to human health.Therefore,the introduction of new structural color materials into self-healing elastomers with covalent adaptive networks to impart bright structural colors is very meaningful.In this study,we first prepared elastomers with excellent self-healing properties by introducing dynamic oxime-carbamate bonds and hydrogen bonds,and then monodisperse silica microspheres were combined with self-healing elastomers to further prepare self-healing elastomers with bright structural colors.(1)A facile two-step approach was proposed to synthesize self-healing elastomers based on the dynamic oxime-carbamate bonds.The hydroxyl-terminated polybutadiene(HTPB)was firstly reacted with isophorone diisocyanate(IPDI)to synthesize the prepolymer with isocyanate groups terminated,followed by further reaction with dimethylglyoxime(DMG)as chain extender to obtain self-healing elastomers.Specially,all-atom molecular dynamics simulations were used to construct the same model as the experiments.Together with experimental characterization of FT IR and ~1H NMR,all-atom molecular dynamics simulations can verify the formation of dynamic oxime-carbamate bonds and hydrogen bonds and.By fixing the ratio of hydroxyl and isocyanate constant,change the molar ratio between HTPB,IPDI and DMG,we found that the mechanical strength increased with the increase of hard segment content.At the same time,the loss factor decreased in the glass transition region and at room temperature.The presence of microphase separation in the elastomer was demonstrated by AFM.Finally,due to the presence of dynamic oxime-carbamate bonds and hydrogen bonds,the self-healing behavior of the elastomer was verified at certain temperature.The mechanism is explained by means of molecular dynamics simulations,where dynamic oxime-carbamate bonds played more important roles than hydrogen bonds.(2)We prepared structural color elastomers of different colors by solvent volatilization methods.Firstly,we synthesized monodisperse silica microspheres of different particle sizes by St(?)ber method with the mixture of ammonia,deionized water,anhydrous ethanol and ethyl orthosilicate under stirring,and then it was added into the self-healing elastomer with dynamic oxime-carbamate bonds to prepare blue,green and yellow structural color elastomers.The microspheres of monodisperse silica with different particle sizes were successfully prepared and the particle sizes were basically in accordance with the requirements,which were verified by SEM and XRD.The reflectance spectroscopy as well as SEM and TEM characterization of the microscopic morphology reveals that the monodisperse silica microspheres are arranged in a short-range ordered amorphous structure in the self-healing elastomer matrix,thus to give the elastomer its structural color.Finally,the structural color elastomers exhibited excellent self-healing properties due to the presence of dynamic oxime-carbamate bonds and hydrogen bonds in the elastomer matrix as characterized by optical microscopy and tensile machines.