Preparation,Properties And Applications Of Chitosan-Based Hydrogels

In this paper,three kinds of chitosan（CS）-based hydrogels were designed to enrich and expand the different applications of intelligent hydrogels.Acrylamide（AAm）,silica（SiO₂）and 2-acrylamide-2-methylpropanesulfonic acid（AMPS）were introduced into CS system to prepare PAAm/CS,P（AAm-co-AMPS）/CS and P（AAm-co-AMPS）/CS-SiO₂ hydrogels respectively.The composition and structure of the hydrogels were characterized by Fourier transform infrared spectroscopy（FT-IR）and X-ray diffraction（XRD）,The morphology of hydrogel was characterized by scanning electron microscope（SEM）and laser confocal microscope.The oil-water separation performance of the PAAm/CS@SSM hydrogel,the dye adsorption performance of the P（AAm-co-AMPS）/CS and P（AAm-co-AMPS）/CS-SiO₂ hydrogels,and the humidity response of the QCM humidity sensor of the P（AAm-co-AMPS）/CS-SiO₂ hydrogel at11-95%RH were investigated.This research mainly focuses on the following three points:1.Firstly,PAAm/CS@SSM membrane with underwater superoleophobicity was prepared by chemical etching and coating methods using stainless steel mesh（SSM）as a substrate.The effects of different etching time and dosage of CS on the surface morphology,roughness and contact angle of underwater oil（OCA）of PAAm/CS@SSM films were studied by scanning electron microscope（SEM）,laser confocal microscope and contact angle measuring instrument,respectively.The wetting conditions and the separation performance of different oil products,different oil-water ratios,and multiple cycles were studied,and the corrosion resistance and wear resistance of PAAm/CS@SSM membrane were also studied.The composition and structure of PAAm/CS hydrogels were studied by Fourier transform infrared spectroscopy（FT-IR）and X-ray diffraction（XRD）.The PAAm/CS@SSM membrane has underwater superoleophobicity,and the OCA of the membranes with content of CS is greater than 150°at different etching times.In the oil-water separation experiment with 20 cycles,the oil-water separation efficiency of the PAAm/CS@SSM membrane are more than 99%,PAAm/CS@SSM membrane also shows high separation efficiency for different oils,and the volume ratio of oil-water mixed solution has little effect on the separation efficiency;The PAAm/CS@SSM film has relatively excellent wear resistance and still maintains the underwater superoleophobic properties after the wear test.2.Using AAm and AMPS as monomers and MBA as cross-linking agent,a three-dimensional network structure was formed by free radical copolymerization,and the linear macromolecular CS was interspersed in it to form a semi-interpenetrating network structure,and SiO₂ particles were introduced to prepare P（AAm-co-AMPS）/CS and P（AAm-co-AMPS）/CS-SiO₂ hydrogels,hydrogel coatings were prepared on glass slides by dipping method,and Fourier transform infrared spectroscopy（FT-IR）and X-ray diffraction（XRD）to characterize the composition and structure of the hydrogel,and the morphology of the hydrogel was characterized by scanning electron microscopy（SEM）.The effects of different content of SiO₂、MBA and monomer ratio（AMPS:CS）on its hydrophilic properties and underwater oleophobic properties were investigated by contact angle measuring instrument.The adsorption properties of P（AAm-co-AMPS）/CS and P（AAm-co-AMPS）/CS-SiO₂ hydrogels for cationic dye methylene blue（MB）were investigated by UV-vis,and the adsorption properties of MB with different concentrations were investigated.Adsorption performance,the maximum adsorption capacity of P（AAm-co-AMPS）/CS and P（AAm-co-AMPS）/CS-SiO₂ hydrogels for MB reached431.863 and 337.590 mg/g,respectively.The analysis shows that the adsorption kinetics of the two hydrogels are consistent with the pseudo-first-order adsorption kinetics model,and the isotherm adsorption behaviors of the two hydrogels are more in line with the Langmuir isotherm adsorption model.3.Using AAm and AMPS as monomers and MBA as cross-linking agent,in situ free radical copolymerization forms a three-dimensional network structure P（AAm-co-AMPS）,in which the linear macromolecules CS are interspersed to form a semi-interpenetrating network structure hydrogel P（AAm-co-AMPS）/CS.The QCM humidity sensor was fabricated by spinning a hydrogel composite membrane on a QCM quartz wafer.The surface morphology and roughness of the QCM humidity sensor were investigated by atomic force microscopy（AFM）and laser confocal microscopy,and blank wafers,sodium dodecyl benzene sulfonate（SDBS）,PAAm/CS and P（AAm-co-AMPS）/CS composite membranes modified by QCM were investigated.Humidity response of QCM humidity sensor in11-95%RH humidity environment,and studied the dynamic responsiveness,response-recovery,repeatability and hysteresis behavior of QCM humidity sensor in 11-95%RH humidity environment of PAAm/CS and P（AAm-co-AMPS）/CS.The humidity sensor modified by P（AAm-co-AMPS）/CS composite membrane showed obvious responses in different humidity environments.Under the humidity environment of 11-95%RH,the adsorption response time of the QCM sensor is 59 s,and the desorption recovery time is 72 s,with good repeatability.The sensitivity of the P（AAm-co-AMPS）/CS humidity sensor is 14.41 Hz/%RH.In addition,compared with the QCM sensor modified by the PAAm/CS composite membrane,the hysteresis characteristics of the sensor were significantly improved after the introduction of AMPS.