Synthesis,Characterization And Application Of Self-healing Materials Based On Fe(Ⅲ)-Hpdca Complexes

The concept of self-healing originates from the self-healing phenomenon in biology.All matter is subject to thermal or mechanical destruction as well as chemical degradation during its active lifetime thus restricting its practical application.Therefore,people,inspired by nature,want to make self-healing polymers to prolong the lifetime of materials.This thesis aims to explore the dynamic properties of self-healing materials based on Fe(Ⅲ)-Hpdca complexes and unveil the relationship between structure,dynamics and self-healing properties.Then,its application to flexible electronic skin is explored by selecting proper polymer backbone.The two main aspects are as follows:1.New insights into the mechanical and self-healing properties of polymers crosslinked by Fe(Ⅲ)-2,6-pyridinedicarboxamide coordination complexesIn order to understand the mechanical and self-healing properties of polymers,we performed the reaction between 2,6-pyridinedicarboxamide and FeCl3 at both neutral and alkaline conditions,and studied the dynamic ligand exchange properties of the resulting model complexes.The results showed that[Fe(Hpdca)2]+was highly dynamic at room temperature,while[Fe(pdca)2]-was not in the same condition.Thus,the FeHpdca-PBCA polymer films had poor mechanical strength but much higher stretchability and better self-healing properties as compared to that of Fe-pdca-PBCA polymer films.It is concluded that the bond strength of cross-linking sites will affect the mechanical strength of polymer networks significantly,while the dynamic behavior of cross-linking sites will endow the polymer with higher stretchability and better selfhealing properties.Such understanding would be helpful for further designing of novel synthetic polymers,which can achieve an optimal balance between the mechanical strength and self-healing performance.2.A highly sensitive self-healing thermistor array and its application in flexible artificial skinA PPG polymer material Fe-Hpdca-PPG400 crosslinked by[Fe(Hpdca)2]+complex was designed and synthesized.This material exhibited excellent self-healing properties and electrical properties with ultra-high temperature sensitivity.The TCR value of Fe-Hpdca-PPG400 was tested to be-18.2%,which is the highest value of the reported ionic polymer materials.Based on the thermodynamic analysis and rheological studies of Fe-Hpdca-PPG400,Tg of Fe-Hpdca-PPG400 was found to have a great impact on TCR valure of the thermistor.Further electrical tests showed that the temperature sensitivity(TCR)of materials in the bulk system was independent of the content of Fe(Ⅲ)ions,but mainly determined by the dynamics of polymer chains.Because Fe(Ⅲ)-Hpdca complexes have sufficient dynamic properties at room temperature,and thus are less affected by temperature.In contrast,the dynamic properties of polymer chains are the critical factors hindering ion mobility.This understanding was an important guidance for the designing and synthesis of ionic thermistor sensors with high sensitivity.Finally,a flexible artificial skin sensor array was fabricated by ink-jet printing,and the real-time temperature measurement of the two-dimensional plane was realized.Real-time,convenience,high sensitivity and durability are the highlights of this flexible skin sensor,which has wide application in flexible electronic devices and medical fields.