Study On The Synthesis And Performances Of Chitosan-based Intelligent Hydrogels

The intelligent hydrogels were prepared using chitosan(CS), polyvinylpyrrolidone (PVP) and/or polyvinyl alcohol(PVA) as raw materials, glutaraldehyde as cross-linking and ammoniumcericnitrate as initiator. The influences of the mass ratio of raw materials, the amount of initiator and cross-linking agent, reaction time and temperature on the distilled water absorption amount of hydrogels were investigated. The measurements of environmental sensitivity of hydrogels were carried out. The hydrogels were characterized by FTIR, SEM,DSC and TG. The main contents of this dissertation are as follows:(1) The appropriate conditions of preparation were obtained. The two kinds of hydrogels are of good swelling ratio and multiple environmental sensitive properties. The addition of PVA increases the content of CS in hydrogels significantly and improves the temperature sensitivity obviously.(2) The CS/PVP hydrogels achieved the maximum swelling ratio of 1700% at pH=4 and 55℃. While the pH value was between 4.0 and 7.0, the change of swelling ratio was gently. While the pH value between 7.0 and 13, the ratio decreased obviously and drastically. And while the pH value was above 13, the change of ratio became gently again. Biodegradation experiment showed that the hydrogelsis of good degradability. The mass loss can reach above 50% after 7 days. Moreover, the hydrogels exhibited fast swelling behavior in the solution with pH=2, and fast deswelling behavior in pH=10.(3) The maximum swelling ratio of CS/PVP/PVA hydrogels was obtained at pH=2 and 45℃. Compared with CS/PVP hydrogels, the temperature sensitivity of CS/PVP/PVA hydrogels improved significantly. Impportantly, it indicated obvious sensitivity at about 35℃. About the pH sensitivity, the key point was 2.0. Moreover, the ternary hydrogels were of good salt sensitivity and degradability.(4) FTIR showed that the prepared hydrogels were of half interpenetrating networks. DSC indicated that freezing water and non-freezing water existed in hydrogels, and content of freezing water was primary. TG indicated that the hydrogels were of good thermal stability. SEM showed that the surface of binary hydrogels was loose and of porous, while that of the ternary hydrogels was relatively smooth and of large and shallow cavity. Moreover, the surface topography of hydrogels was influenced by the properties of solution obviously.