Preparation Of Carboxymethyl Cellulose-based Microgels And Their Application In Hydrogel Sensor

Microgels are a micron size hydrogel colloid,which has the characteristics of softness,deformability and penetration,combining the typical characteristics of macromolecules,colloids and surfactants,and can be applied as an adsorbent to wastewater treatment,such as adsorption dyes.Microgels can also be used to prepare a high-performance hydrogel.Hydrogels are a class of hydrophilic polymers with a three-dimensional mesh structure that are insoluble in water and organic solvents.Because hydrogels have the advantages of soft texture,good swelling,good biocompatibility,non-toxicity and degradability,it is widely developed and applied to biomedicine,building materials,flexible materials and other fields.In recent years,microgel-enhanced hydrogels(MR gels)could be developed as candidates for wearable sensors.But efforts have been made to increase the mechanical strength of hydrogels,and the resistance to ion migration has increased,resulting in a decrease in the sensitivity of hydrogel sensors.Therefore,this project achieves high sensitivity of hydrogel sensors by designing a strategy of microgel-reinforced hydrogel.The research content of this paper is as follows:(1)Sodium carboxymethyl cellulose /poly(acrylic acid)(CMC/PAA)microgels were prepared by visible-light-triggered free radical polymerization using sodium carboxymethyl cellulose and acrylic acid as raw materials.Then the microgels were used as an adsorbent for the removal of methylene blue dye(MB)to study the effect of microgels on the adsorption performance of MB under different conditions,such as different components of microgels,initial concentration of MB,temperature,p H,ionic strength and adsorption time.The results showed that the microgels had high adsorption capacity(1479 mg/g)and removal efficiency(97%).In addition,the adsorption mechanism of microgels on MB was further studied by adsorption kinetics and adsorption isotherms.The 5 adsorption-desorption cycle experiments indicated clearly that the microgels has renewable capacity.More importantly,CMC/PAA microgels could settle naturally after finishing adsorbing MB.(2)The as-prepared CMC/PAA microgels in the above chapter was used as an enhancer,acrylamide(AM)as a monomer,lithium chloride(Li Cl)as a conductive element,and a microgel-reinforced polyacrylamide conductive(CMC-PAA/PAAm/Li Cl)hydrogel was synthesized.The UV testing showed that the hydrogel had good transmittance(82%)at room temperature.Tensile tests indicated that the introduction of microgels significantly improved the tensile properties of hydrogels.The strain sensor based on the CMC-PAA/PAAm/Li Cl hydrogel had good strain sensitivity(GF=5.46)and a wide strain sensing range(0-500%),which could be used to monitor and record large and subtle human movements(such as fingers,wrists,knee bends,breathing,swallowing and pronunciation).(3)CMC-PAA microgels as an enhancer,AM as a monomer,N,N’-methylenebi-sacrylamide(MBA)as a crosslinker,a two-step UV-initiated free radical polymerization method was used to prepare a dual-network crosslinked polyacrylamide hydrogel(DN-CMC-PAA/PAAm).When the MBA content was 1 mg,the tensile strength and modulus of elasticity of the hydrogel were 147 k Pa and 60 k Pa,respectively,and transmittance was higher than 92% at room temperature.The transparent wearable strain sensor based on the compound hydrogel had good strain sensitivity(GF=9.01),a wide strain sensing range(0-800%)and excellent durability and reproducibility(1000 cycles),which could be used to monitor and record large and subtle human movements in real time,such as fingers bending,wrists bending,elbow bending,swallowing and pronunciation.