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|標題:||Preparation and Characterization of pH-responsive hydrogels by two-step free radical polymerizations
In this study, pH-sensitive hydrogels were prepared by two-step free radical polymerizations. First, poly (N-hydroxysuccinimide) (NAS) was obtained by polymerization of NAS using 2,2'-asobisisobutyronitrile as an initiator. Poly (NAS) was subsequently reacted with 2-hydroxyethylmethacrylate in the presence of triethylamine to give rise to vinyl-group carrying copolymer, followed by hydrolysis of NAS comonomers in aqueous buffer pH 8.5. Second, pH-sensitive hydrogels were prepared by copolymerization of the corresponding copolymers with N-isopropylacrylamide (NIPAAm) using ammonium peroxydisulfate and N,N,N',N'-tetramethylethylene as an initiation system.
pH-dependent swelling of hydrogels was strongly influenced by the effective network density and NIPAAm content of hydrogels. The greatly reduced swelling of pH-responsive hydrogels is primarily a consequence of the increased cross-linking density of the networks upon the addition of NIPAAm during the second-step copolymerization. At high pH, hydrogels with higher NIPAAm contents showed reduced swelling. On the other hand, at low pH, the hydrogels significantly deswell probady due to the high extents of hydrogen bonding between the carboxyl group and amide group within hydrogels.
利用二階段式自由基共聚合製備酸鹼應答型水膠。於第一階段中，以N-acryloxysuccinimide (NAS)單體聚合成poly( NAS )，並與HEMA進行轉脂化反應，使高分子主鏈帶有雙鍵以提供第二次自由基共聚合反應。接著將高分子置於Tris buffer( pH 8.5 )中以進行水解反應，使高分子主鏈帶有酸鹼應答型官能基。於第二階段中加入NIPAAm共聚合的目的為提供架橋作用並提高水膠交聯密度，並使水膠膨潤時不易破裂。
|Appears in Collections:||化學工程學系所|
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