快速响应的温敏性聚(N-异丙基丙烯酰胺)水凝胶 Ⅱ.热力学行为及水的状态研究

FAST RESPONSIVE THERMOSENSITIVE POLY(N-ISOPROPYLACRYLAMIDE) HYDROGELS Ⅱ. THERMODYNAMIC BEHAVIOR AND WATER STATE IN THE HYDROGELS

对使用CaCO3为成孔剂合成的快速响应的温敏性聚 (N 异丙基丙烯酰胺 ) (PNIPA)水凝胶进行了热力学行为和水的状态研究 .热力学研究表明 ,多孔结构的PNIPA水凝胶的平衡膨胀比随着反应物中CaCO3含量的增加而增加 ,随着交联剂浓度的增加而显著减小 ,但相转变温度均不受影响 .在水溶液中加入NaCl则使PNIPA水凝胶的相转变温度 (LCST)线性减小 .利用DSC分析了水凝胶中水的存在状态 ,证明了上述多孔PNIPA水凝胶中存在三种不同状态的水 。

Thermodynamic behavior and water state in the hydrogels were investigated for the fast responsive thermosensitive poly( N isopropylacrylamide) hydrogels which were prepared by adding CaCO 3 as a pore foaming agent during the polymerization. The results indicated that the swelling ratio increased as the content of CaCO 3 in the reactants increased. The effect of crosslinking agent on the swelling ratio showed that the more the crosslinking agent content, the lower the swelling ratio. The gel phase transition temperature was not influenced by the content of CaCO 3 and crosslinking agent, but it decreased linearly as the NaCl content in water solution increased. DSC was used to study the state of water in the porous hydrogels swollen in deionized water and different content of NaCl solution. Results showed that three states of water exist in all these porous hydrogels. The effect of the content of CaCO 3 and ionic strength on the three states of water was also investigated.