Preparation And Characterization Of Self-healing Elastomers And Their Application In Flexible Sensors

Polymer materials play a very important role in the field of flexible sensing.At present,common commercial polymer materials are often unable to repair the mechanical damage caused by external factors,resulting in a decrease in sensor service life.To address this problem,researchers have developed polymer materials with self-healing properties and successfully applied them to flexible electronic devices.However,the exploration towards flexible sensors with reliable self-repairing capability,excellent cycling stability,high sensitivity,and wide detection range.Elastomers are an important category of polymer materials for as sensor substrate.This thesis focuses on the preparation,performance characterization,and evaluation research of new self-healing elastomers.The relationship between their structure and properties was analyzed,and their application in the field of flexible sensing was studied.Multiple reversible interaction units（disulfide,imine,and hydrogen bonds）were introduced into the elastomer network to obtain self-healing elastomer（PIH₂T₁-tri）.The PIH₂T₁-tri exhibited good mechanical properties with tensile strength and elongation at break of 1.41 MPa and 672%,respectively,and showed appreciable self-healing ability（self-healing efficiency=91%）.An electronic flexible strain sensor（PIH₂T₁-tri/CNT-3）was obtained by spraying a thin conductive layer of carbon nanotubes（CNT）on the surface of PIH₂T₁-tri.It exhibited effective conductivity and self-healing properties.It also had high gauge factor（GF=24.1）,short response time（120 ms）,and long-term durability（4000 cycles）.In addition,it was found that GF increased with the increase of the thickness of the conductive layer and was not affected by the component of the elastomer.The PIH₂T₁-tri/CNT-3 sensor could also detect the movement of different parts of the human body in real time.This work provides a new type of self-healing elastomer followed by investigating the corresponding flexible strain sensor,which provides new idea for the development of flexible sensing materials.A polyurethane elastomer（PU）containing reversible dynamic disulfide and hydrogen bonds was synthesized by a one-pot method.It had the structural characteristics of microphase separation.After mixing with lithium bis（trifluoromethane）sulfonimide（Li TFSI）,a series of new self-healing solvent-free ionic conductive elastomers（ICEs）were obtained.Among them,ICE-2 exhibited good ionic conductivity(room temperature,2.86×10^-6 S/cm),high transparency（>89%）,excellent mechanical properties（tensile strength of 3.06 MPa,elongation at break of 1760%,and fracture energy of 14.98 k J/m²）,appreciable self-healing ability（self-healing efficiency>90%）,good environmental stability,and excellent recyclability.The ionic flexible sensor constructed by ICE-2 could not only detect temperature changes,but also had satisfactory strain sensing properties,such as linear response（0～200%strain range,GF=0.94）,fast response（250 ms）,and good cycle stability（2000 cycles）.At the same time,it can also accurately and sensitively detect various human movements,including joint movements and micro-expression changes.This study provides a simple,effective and“green”strategy for the design of ionic flexible sensors.