| With the development of fields related to sensing materials,flexible sensing materials have emerged after the traditional rigid sensing materials and semi-rigid sensing materials such as metal-organic frameworks.Ionic liquid gels formed by filling with ionic liquids exhibit excellent properties such as good flexibility,wide operating temperature range,high thermal stability,and high electrical conductivity,and have become a development direction for flexible sensing materials,showing great potential in electronic fields such as polymer thin-film transistors,solid electrolytes,and flexible sensors.Ionic liquid gels can be used for flexible conductive materials by using ionic liquids as charge carriers in solid form or by modifying the conductive materials themselves.However,the preparation of efficient ionic liquid gels with good mechanical strength and high conductivity remains a major challenge.In this paper,graft-modified cellulose（CNC）was used as the matrix material and ionic liquid was used as the conductive element to prepare a conductive ionic liquid/modified cellulose hydrogel,and the preparation conditions of the hydrogel were optimized by performing tensile,light transmission performance,and conductivity tests on the resulting hydrogel.And the flexible sensing performance tests were conducted with the hydrogels made under the optimal conditions.（1）Firstly,two graft modifications were performed on cellulose,the matrix material of the ionic liquid gel.Two substances,acrylic acid（AA）-acrylamide（AM）and acrylic acid（AA）-2-acrylamide-2-methylpropanesulfonic acid（AMPS）,were grafted and polymerized on cellulose to obtain CNC-P（AA/AM）and CNC-P（AA/AMPS）,respectively.The graft-modified fibers were also characterized by infrared spectroscopy and confirmed to have been grafted successfully.The two graft-modified cellulose were utilized as the matrix materials for the subsequent preparation of hydrogels,respectively.（2）Two ionic liquids,1-propenyl-3-methylimidazolium chloride（[AMIM]Cl）and 1-ethyl-3-methylimidazolium bromide（[EMIM]Br）,were synthesized and characterized by both IR spectroscopy and NMR,confirming the successful synthesis of these two ionic liquids and their use for the next gel preparation.（3）Hydrogels were prepared by adding 0%,5%,10%and 15%by mass of ionic liquids to the graft-modified cellulose,and a total of 14 hydrogels of four types were obtained.These 14hydrogels were compared for tensile strength,transmittance,and electrical conductivity,and it was found that CNC-P（AA/AMPS）-[EMIM]Br-10%hydrogels had better performance,and their maximum tensile strength could reach 53 MPa,transmittance in the range of 400 nm-700 nm remained between 85%～90%,and electrical conductivity could reach 4.6×10-7 S/m.（4）The sensor was made of CNC-P（AA/AMPS）-[EMIM]Br-10%hydrogel and tested for respiration,bending,and compression sensing.It was found that the sensor could distinguish high-frequency respiration and low-frequency respiration well,maintain monitoring accuracy after 200 bending cycles,and clearly distinguish three bending states of 30°,45°,and 60°.It can maintain the stable output of the test signal after 400 times of compression cycle test.And it can monitor the different movement states of human elbow,wrist,knee and foot in real time.The hydrogel can be used in flexible wearable electronic devices or electronic skin,which has practical development value in medical,health monitoring and sports fields. |
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