Preparation And Application Of Self-healing Thermal Response Ionogels

Ionogel is a kind of gel material formed by immobilizing ionic liquid in a three-dimensional network structure,which has good thermal stability,flexibility and electrochemical properties,and has a wide application prospect.Ionogels have been widely used in energy storage and conversion devices,intelligent displays,separation membranes,and catalytic membranes.Among them,thermal responsive ionogels have attracted people’s attention because their physical and chemical properties will change reversibly when subjected to external temperature changes.However,in the process of long-term use,ionogels will inevitably suffer mechanical damage,resulting in the decline or disappearance of various properties,thus limiting the application of ionogels.Through the introduction of external heal agents or the construction of dynamic covalent bonds and supramolecular forces,when ionogel is damaged,it can heal the damage spontaneously or under the stimulation of external conditions,and restore its original performance,so that the service life of ionic gel is extended.At present,great progress has been made in the research of self-healing ion gels,but there are still some problems,which make ionogels have great limitations in practical application.For example:（1）Poor mechanical properties make the material easily damaged in the process of use.Even if the damage can be healed,the application range of ionogel is greatly limited;（2）Harsh healing conditions.Currently,the healing conditions of self-healing ionogels with high strength are relatively harsh,such as high temperature,ultraviolet light or solvo-assisted,which limit the repair ability of ionogels in practical application.Therefore,it is of great significance to achieve ionogels with good mechanical strength and the ability to repair under relatively mild conditions.To solve the above problems,this thesis prepared thermal response ionogels with an excellent self-healing performance by adjusting the type and density of supramolecular forces in the polymer networks.By adjusting the content of ionic liquid and inorganic filler,good unity of self-healing and thermal response can be achieved.The specific research contents are as follows:1.In the first work,we loaded binary ionic liquids into self-healing polyurethanes containing reversible multiple hydrogen bonds acylsemicarbazide（ASCZ）groups,and prepared self-healing thermochromic ionogels with good mechanical and environmental stability,anti-fog ability,high transparency,and solar regulation ability.It has proved its feasibility as a reliable and long-life smart window.The self-healing thermochromic ionogel can switch between transparent（20°C）and opaque（40°C）without leakage or shrinkage due to the reversible phase separation of ionic liquids that is constrained within the ionogel.The ionogel has the highest solar modulation capacity(T_sol=83%)and transparency(T_lum=95.1%)of any thermochromic material that has been reported,maintaining this excellent solar modulation ability very well after 1000 heating-cooling transitions,stretching and bending,at-30°C,60°C,90%RH and vacuum for 2 months.The formation of multiple hydrogen bond crosslinking between the ASCZ moieties of the polymer helps to improve the mechanical strength（5.58 MPa）of the ionogel and allows the thermochromic ionogel to spontaneously heal damage and recover completely at room temperature without loss of thermochromic ability.The self-healing thermochromic ionogel can achieve effective building insulation and has a broad application prospect as a smart window.2、In the second work,we choose polyethylene glycol as the main chain of polyurethane because of its good compatibility with ionic liquid,and use adipic dihydrazide as chain extender to prepare self-healing high strength polyurethane.On this basis,1-ethyl-3-methylimidazole bis（trifluoromethanesulfonyl）imide ionic liquid was loaded in polyurethane to prepare high-strength high sensitivity and self-healing ionogel,and its thermal response ability as a temperature sensor was explored.The good electrochemical properties of ionic liquid and the good affinity between ionic liquid and PEG segment endow ionogel excellent thermal and electrochemical stability,which provides a guarantee for its use as an excellent ionic conductor.Ionogels have potential temperature sensing capabilities due to their conductivity changes with temperature.The prepared ionogel temperature sensors has high sensitivity(-2.4%·°C^-1)and stable and repeatable temperature sensing capabilities.In addition,the multiple hydrogen bond crosslinked polyurethane network provides the ionogel with high mechanical strength（27.7 MPa）and excellent self-healing（99.3%self-healing efficiency at 80°C）.The ionogel can spontaneously healing after damage and recover its mechanical and thermal responsiveness,making it stable and reliable for long-term use as a temperature sensor.The ionogel with high strength,sensitivity and self-healing capability provides a reliable direction for the preparation of temperature sensors.