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標題: 酸鹼敏感型聚葡萄糖水膠: 丙烯酸對水膠製備與膨潤性質影響
作者: 林一峰
關鍵字: dextran;水膠;hydrogel;swelling ratio;酸鹼應答;膨潤程度
出版社: 化學工程學系
In this study, pH-sensitive dextran hydrogels were prepared from conjugation of dextran with glycidyl methacrylate (GMA), followed by copolymerization of modified dextran with acrylic acid (AAc). The incorporated amount of AAc in hydrogels was determined by FTIR spectroscopy. The results indicate that the molecular weight and effective network density of hydrogels increase with addition of small amounts of AAc. The gel yield was reduced by addition of higher amounts of AAc owing to the ionic interaction of TMEDA with AAc and subsequent inhibition of TMEDA initiation. The effect of AAc on the increase in polymerization of MA-dextran was also confirmed by size exclusion chromatography.
pH-dependent swelling of hydrogels was strongly influenced by the effective network density and acrylic acid content of hydrogels. The change in the dissociation degree of acrylic acid in hydrogels and differences in the concentrations of ionized species inside and outside hydrogel as a function of pH and neutral salt concentration were calculated based on the Donnan equilibrium and Debye-Hckel theory. The calculated results indicate a good correlation with corresponding pH/salt-dependent swelling data.

將鍵結glycidyl methacrylate(GMA)之聚葡萄糖(dextran)與acrylic acid(AAc)進行自由基共聚合,以製備酸鹼敏感型dextran水膠,並以FTIR檢測水膠中AAc的含量。實驗中探討AAc對水膠製備及膨潤性質的影響,結果顯示添加AAc會增加水膠的有效交聯密度及在較低的MA鍵結程度(degree of substitution, DS)時,可促進水膠的形成。但當我們進一步提高AAc的濃度,反而導致水膠聚合不完全、甚至無法完全形成。由size exclusion chromatography(SEC)實驗顯示AAc的添加能增加高分子分子量,將原本距離較遠的MA(-C=C-)鍵結起來而有類似架橋的作用。此外,利用水膠膨潤理論在不同pH值下比較水膠膨潤的應答行為,發現其膨潤應答程度主要受有效交聯密度與AAc所提供的離子滲透壓的綜合效應所影響。同時我們發現水膠的膨潤會隨buffer中鹽類濃度(NaCl)的增加而下降。由數據顯示解離程度(a)隨NaCl濃度的提升而呈現下降的趨勢。水膠中的可解離官能基(AAc)表現出的pKa值受到溶液中鹽類離子的影響。由於離子交換的緣故,適當的鹽類濃度有助於解離的產生。另外,高鹽類濃度(NaCl)時由於-COO-會和Na+ 形成離子鍵使得有效解離度下降。
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