Construction And Property Of PVA-based High Mechanical And Conductive Physical Gel

Hydrogel is a kind of soft and wet material that contains a lot of water and has a three-dimensional cross-linked network structure.They are capturing intensive attention for versatile applications in tissue engineering,drug carriers,and flexible wearable electronic devices on account of adjustable physical and chemical properties.However,there are some problems to be confronted with conventional hydrogel:poor mechanical stability,deficient reparability after damage and limited application temperature range.Therefore,the construction of multifunctional hydrogel is of great significance for the application of new hydrogel materials.Herein,a physical gel with high mechanical properties,excellent freezing resistance and self-healing properties was constructed based on poly（vinyl alcohol）（PVA）.Then,hydrogel based wearable flexible sensors and triboelectric nanogenerators were assembled separately and their applications in the fields of health monitoring and energy harvesting were investigated.The main research contents and results are as follows:（1）Preparation of multi-crosslinked PVA hydrogel and its application in flexible sensors.A multi-crosslinked poly（vinyl alcohol）（M-PVA）hydrogel with outstanding mechanical properties,ionic conductivity and freezing resistance was constructed by importing chain entanglement interaction and complexation between Fe³⁺ions and hydroxyl groups into the microcrystalline network through immersion treatment in Fe₂（SO₄）₃ solution.The three reversible and reconstructable crosslinking within M-PVA hydrogel worked in tandem to achieve ultra-stretchability（1120%）,super-compressibility（≥98%）,high toughness(48.5 MJ m^-3),fast self-recoverability and superior fatigue resistance.Meanwhile,introduction of Fe³⁺and SO₄^2-ions endowed the M-PVA hydrogel with good ionic conductivity and remarkable anti-freezing property（-50°C）.The M-PVA hydrogel can be assembled to be a multi-model sensor to detect large range elongation（～900%）,compression（～70%）,bend and touched pressure（up to 4.6 MPa）,with high sensitivity（GF=3.8,ε=900%）.In addition,the hydrogel sensor can serve as a wearable sensor to detect full-range human activities,including speaking,fingers bending and treading behaviors even at low temperature.Based on the feasible and simple preparation method and excellent properties,M-PVA hydrogels have a wide range of potential applications in flexible electronics,motion recognition and intelligent robots.（2）Fabrication of self-healing PVA/HPAAm/Mxene/Gly double physical network organohydrogel and its application in flexible devices.Firstly,conductive and photothermally active Ti₃C₂T_xMXene was incorporated into the PVA/HPAAm hydrogen bond crosslinked-hydrophobic association double network hydrogel,and then the resultant hydrogel was soaked in glycerin to construct a self-healing,water-retaining and anti-freezing PVA/HPAAm/MXene/Gly physically double cross-linked network organohydrogel.The introduction of MXene endow the organohydrogel with good conductivity(4 S m^-1),and can effectively enhance the self-healing ability.The organohydrogel can be highly efficiently self-healed（95%）under the exposure to infrared（IR）light in 30 min.The PVA/HPAAm/MXene/Gly organohydrogel possessed excellent freezing resistance（-50°C）and moisture retention according to the glycerin-water binary solvent.The organohydrogel based wearable sensor showed high sensitivity（GF=4.56,ε=600%）,and can monitor human activities such as joints movement and subtle facial expressions in real time.Importantly,the organohydrogel-based device can act as a triboelectric nanogenerator with excellent energy harvesting capabilities,giving an open circuit voltage(V_OC)of 85 V,short circuit current(I_SC)of500 n A and short-circuit transferred charge(Q_SC)of 30 n C.The dual performance of strain sensing and energy harvesting shows that PVA/HPAAm/MXene/Gly organohydrogels have great application potential in high-performance wearable devices and self-powered devices.