Study Of Multifunctional Polyurethane Based On Synergy Of Dynamic Disulfide Bonds And Hydrogen Bonds

The shape-memory effect,self-healing effect and photothermal performance of polymer materials provide many new ideas for the research and use of polymer materials.Among them,shape-memory effect can make the polymer material change between several specific shapes,and it is widely used in the fields of soft actuators,soft robots,and drug carriers.Self-healing effect can make the polymer spontaneously repair the damage and extend the service life of the polymer material.Photothermal performance is used as a non-contact heating method,so that the material can change the temperature remotely,locally,and accurately.These characteristics make polymer materials have a wider range of applications,however,in actual use,single smart behavior is difficult to fit the inclusive demand.Materials often do not undergo simple and regular damage,and the shape-memory process is also limited to a certain part of the material.Therefore,it is necessary to integrate more smart behaviors such as shapememory effect,self-healing effect,photothermal property,and other behaviors into a single polymer network,so that the prepared multifunctional polymer can be more in conformity with actual needs.In this study,we prepare two different types of multifunctional thermoplastic polyurethane urea of PCL-PUSS and PTMEG-PUSSC.The physical and chemical structures of two types of polyurethane urea are studied,and the changes of hydrogen bonds and dynamic disulfide bonds with temperature are investigated.Through temperature-dependent infrared spectroscopy and two-dimensional infrared spectroscopy,it is found that the hydrogen bonds are gradually destroyed with the increase of temperature.Through temperature-dependent Raman spectroscopy,it is found that the content of dynamic disulfide bond reduces under the medium temperature conditions.Subsequently,we investigate the performance and various smart behaviors of the first type of thermoplastic polyurethane PCL-PUSS.Dilatometry experiments and stress-relaxation curves characterize the viscoelasticity of the material network,which prove that there are a large number of hydrogen bonds in the polymer,so that the thermoplastic polyurethane urea exhibits similar characteristics with vitrimer.Dynamic mechanical analysis and bending angle recovery experiment have qualitatively and quantitatively investigated the shape-memory effect of the material,and prove that PCL-PUSS,which is based on hydrogen bonds as the stationary phase and soft segment crystals as the reversible phase,has great shape-memory performance,and the performance is consistent with the hydrogen bonds in the material.The mechanical properties and self-healing properties of PCL-PUSS are investigated through the stress-strain curve,which prove that the synergistic effect of hydrogen bonds and reversible bonds give the polymer great mid-temperature self-healing properties,and at the same time makes its mechanical properties first strengthened and then weakened.The solid-plasticity and liquid-plasticity of PCL-PUSS30 are investigated,and two types of soft actuators are prepared by volatile solvent and modular splicing technology,which realize the response to external stimuli and braking.Finally,we investigate the performance and various smart behaviors of the second type of thermoplastic polyurethane PTMEG-PUSSC.The viscoelasticity of the material network is characterized by the stress-relaxation curve and dynamic mechanical analysis,which prove that there are hydrogen bonds between the soft and hard segments and between the polymer molecular chain and the surface of the aminated carbon nanotube in the polymer.The mechanical properties and self-healing properties of PTMEG-PUSSC are investigated through the stress-strain curve,which proves that the synergistic effect of hydrogen bonds and reversible bonds gives the polymer great body temperature self-healing properties as well as enhanced mechanical properties.Through the photothermal test,the influence of the carbon nanotube content and the intensity of the near-infrared light on the photothermal performance are investigated.Finally,we prepare PTMEG-PUSSC10 into soft conductors,and reset its shape and sensitivity through remote heating,which prove that the material has potential applications in the field of flexible electronics and wearable devices.