Room-temperature Construction Of The High-performance Cellulose-based,ionic Conductive Hydrogel Via The AlCl₃/ZnCl₂ Solvent

As an ideal new flexible electronic material,the development of ionic conductive hydrogel conforms to the national innovation driven high-quality development strategy.Under the dual drive of oil resource scarcity and environmental pollution,research on the rational utilization of renewable biomass has received widespread attention.Cellulose is the most abundant and high-quality carbon sink resource in nature,and considered one of the important raw materials to achieve the"dual carbon"goal.However,the large number of hydroxyl groups on the cellulose molecular chain make it unable to melt and dissolve in water or conventional solvents,greatly limiting the efficient utilization of cellulose.In addition,the dense cellulose network structure will also affect the conductivity and mechanical properties of cellulose-based ionic conductive hydrogel,thus hindering the development of cellulose-based ionic conductive hydrogel.It is particularly urgent to build high-performance cellulose-based ionic conductive hydrogel based on green processing technology to meet the demand of emerging high-tech industries for new materials.To address the above key issues mentioned,this paper proposes to use the AlCl₃/ZnCl₂ solvent system developed by our research group,which can quickly dissolve cellulose with low degradation at room temperature.In this study,AlCl₃/ZnCl₂ solvent played three roles:one was a green and efficient cellulose solvent;The second was the catalyst;The third was functional additive.In AlCl₃/ZnCl₂ cellulose solution,AlCl₃ and ZnCl₂ was used as catalyst,and introducing a second layer of elastic network at room temperature to regulate the dense network structure of cellulose,thereby regulating the mechanical and electrical properties of cellulose-based material;Meanwhile,AlCl₃ and ZnCl₂ endowed the material with conductivity,water retention,and anti-freezing performance.In this paper,based on the AlCl₃/ZnCl₂cellulose solution system,a control method for preparing cellulose-based ionic conductive hydrogel with high conductivity and strong mechanical properties at room temperature will be established.The main research content and results are as following:（1）Based on AlCl₃/ZnCl₂ solvent system,cellulose/polyacrylic acid（Cel/PAA）ionic conductive hydrogel was prepared by introducing flexible monomer acrylic acid and polymerizing with cellulose network at room temperature.So as to realize the adjustment of the network of cellulose-based ionic conductive hydrogel.In addition,by exploring the regulation and mechanism of cellulose and polyacrylic acid on the network structure of hydrogel.The mechanism of Al³⁺and Zn²⁺rapid activation of initiators was revealed.The mechanism of catalyst and establishment of the second elastic network in AlCl₃/ZnCl₂ cellulose solution at room temperature was clarified.By comparing the network,the effect of network structure on the mechanical and conductive properties of hydrogel was demonstrated,and the advantages of the loose lamellar structure of the composite hydrogel were further confirmed.Compared with pure cellulose hydrogel,the compression of the Cel/PAA composite hydrogel was significantly improved to 80%,and its conductivity increased by75.3%.In addition,its stress was enhanced over 2 times more than pure PAA hydrogel.The Cel/PAA composite hydrogel has excellent compressibility,conductivity（2.70 S/m）,water retention（90%）,and maintained good conductivity stability at low temperature（-45℃）.In addition,the composite hydrogel had excellent universality in the field of 3D printing functional materials.（2）Although the network structure of cellulose-based hydrogel was successfully adjust by acrylic acid in the previous chapter and improved the mechanical and conductive properties.Cel/PAA ionic conductive hydrogels still have weak adhesion.When Cel/PAA ionic conductive hydrogel is used as solid electrolyte,it is easily to separate from the electrode.Therefore,on the premise of ensuring the mechanical and electrical properties of the hydrogel,it is critical to introduce appropriate groups to enhance the adhesion of hydrogel.Based on the above problems,this chapter introduced the elastic monomer acrylamide into the AlCl₃/ZnCl₂ cellulose solution,and made full use of rich amide group to realize the strong interface between cellulose/polyacrylamide（Cel/PAM）ionic conductive hydrogel and the surface of various materials,thus enhancing the adhesion of hydrogel.This chapter systematically explored the interaction between cellulose network and polyacrylamide network,proving that the introduction of polyacrylamide can effectively enhance the binding force between the two networks.In addition,the composite system can improve the compressibility and conductivity of cellulose-based ionic conductive hydrogel by adjusting the cellulose network structure.Compared with pure cellulose hydrogel,the compression of the Cel/PAM composite hydrogel was significantly improved by 77.8%,and its conductivity increased by 20.6%.The Cel/PAM composite hydrogel exhibited good compressibility（80%）,water retention（95%）,and conductivity（2.54 S/m）.In addition,the composite hydrogel could work stably in a low temperature environment（-45℃）,and still maintain excellent conductivity after 30 days.（3）In the previous chapter,Cel/PAM ionic conductive hydrogel with strong adhesion was successfully prepared by introducing amide group.However,Cel/PAM ionic conductive hydrogel has weak mechanical strength.Therefore,inspired by the strengthening mechanism of nano cellulose in hydrogel,we designed a"fiber reinforced structure"to enhance the mechanical properties of Cel/PAM ionic conductive hydrogel.In this chapter,we made full use of the advantages of AlCl₃/ZnCl₂ solvent system to prepare a uniform micron cellulose/cellulose/polyacrylamide（CMF/Cel/PAM）ionic conductive hydrogel by"one pot"method at room temperature.By comparing the physical and chemical properties of composite hydrogel with different solubility of cellulose,it is found that composite hydrogel containing micron cellulose fibers showed stronger storage modulus and compression stress.It verified that micron cellulose fibers embedded in the cellulose/polyacrylamide composite network can play a strong role in supporting the skeleton and enhance the mechanical properties of hydrogel.The results showed that CMF/Cel/PAM composite hydrogel had good compression performance（80%）,mechanical strength（400 KPa）,and electrical conductivity（1.85 S/m）.It maintained good electrical conductivity stability in the low temperature environment（-45℃）,and its weight remained at 95%after a long time of placement,which broadened the application prospects in the field of flexible sensing.