| Summary: | 碩士 === 國立聯合大學 === 化學工程學系碩士班 === 104 === In this study, a bi-functional thermal/pH responsive hydrogel composed of poly(N-isopropylacrylamide) (PNIPAAm) and poly (acrylic acid) (PAA) was synthesized by photo-polymerization. PAA were introduced to influence serveral behaviors of the PNIPAm hydrogels, such as the swelling ratio, lower critical solution temperature (LCST), responsiveness, swelling thermodynamics and kinetics expansion mechanism. Experimentally, using a differential scanning calorimetry (DSC) analysis the thermal behavior of water molecules in the hydrogel and the expansion of thermodynamics, as well as qualitative and quantitative the situation and content of water molecules in the hydrogel and interaction mechanism between hydrogel and water molecules. The results show that when PNIPAAm hydrogel add 30mol% of AA monomer (PNA3), hydrogels have superior sensitivity to temperature-pH dual response characteristics in alkali solution and pure water. At high temperature the enthalpy change (ΔH) and entropy change (ΔS) decrease, because of the hydrophobic hydration and shrinkage of the molecular chain in poly(NIPAAm/AA) hydrogels. In addition, the mechanism exponent (n) of the PNA3 hydrogel in acid or pure water is much less than 0.5, thus it is a part of "Less Fickian". Shows that it’s not conducive to the spread of water. However the mechanism exponent (n) of PNA3 in an alkaline environment is close to 0.5, it is the most consistent with Fick's diffusion mechanism, which means that water permeation rate can be regulated.
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