Investigation on the mechanism of the volume phase transition of gels and the effect of electrostatic interaction

凝胶体积相变机理及静电相互作用效应研究

• 批准号: 08454184
• 负责人: MAEDA Hiroshi
• 金额: $ 4.99万
• 依托单位: KYUSHU UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08454184/
• 关键词: Gel; Volume phase transition; Calorimetry; Thermo-sensitive gel; N-isopropylacrylamide; pH titration of gels

We have investigated the effect of the introduction of ionized groups or hydrophilic groups into N-isopropylacrylamide (NIPA) gel on the volume phase transition. Copolymer gels NIPA with acrylic acid, stirene sulfonate, and acrylamide were prepared and their swelling behaviors were examined. We have found that the transition like swelling behavior of NIPA gels completely disappeared by the introduction of very small amounts of electric charges. This effect of electric charge is, however, suppressed by the addition of salt. Differential scanning calorimetry was also carried out on the NIPA gels and the copolymer gels.I.Thermal behavior of NIPA gels. For a gel of large size, a broad but clear endothermic peak was observed near the transition temperature even if the volume change of gel is continuous with temperature. This indicates that the dehydration of gel chains, which drives, the volume phase transition, is an endothermic reaction. For a gel of the smallest size, the two successive … More endothermic peaks were observed for the volume phase transition near the transition temperature.II.Thermal behavior of copolymer gels. We have found for the gels containing the ionized groups that the volume change is continuous with temperature and the corresponding enthalpy change is small. Two explanation might be possuble, the dehydration is suppresed in spite of the reduced volum, or the endothermic energy due to the dehydration is compensated with an exothermic energy of some unknown mechanism. We have found that the reduced reaction enthalpy increases up to the original level by adding salt. We have found a new type of volume phase transition for copolymer gel of NIPA and acrylic acid at pH=2, even when the monomer content of the latter was as high as 10%. The thermal behavior including the endothermic energy was found to be the same as that of NIPA gel except for that the transion temperature was low. This indicates that the hydrophobicity of unionized acrylic acid is the same as that of NIPA. Less

我们研究了在 N-异丙基丙烯酰胺 (NIPA) 凝胶中引入电离基团或亲水基团对丙烯酸、苯乙烯磺酸盐和丙烯酰胺的共聚物凝胶 NIPA 的体积相变的影响，并检查了它们的溶胀行为。发现通过引入极少量的电荷，NIPA 凝胶的类似溶胀行为的转变完全消失，然而，这种电荷效应被抑制。还对NIPA凝胶和共聚物凝胶进行了差示扫描量热法。一、NIPA凝胶的热行为 对于大尺寸的凝胶，即使在转变温度附近也观察到宽而清晰的吸热峰。凝胶的体积变化随温度连续变化，这表明驱动体积相变的凝胶链脱水是吸热反应，对于最小尺寸的凝胶，两个连续的反应。在转变温度附近观察到体积相变的吸热峰。二、共聚物凝胶的热行为我们发现含有电离基团的凝胶的体积变化随温度连续变化且相应的焓变很小。可能的是，尽管体积减小，但脱水仍被抑制，或者由于脱水而产生的吸热能被某种未知机制的放热能所补偿。通过添加盐，降低的反应焓增加到原始水平我们发现，即使当后者的单体含量高达 2 时，NIPA 和丙烯酸的共聚物凝胶也会发生一种新型的体积相变。发现除了转变温度低之外，包括吸热能在内的热行为与NIPA凝胶相同，这表明未电离丙烯酸的疏水性与NIPA凝胶相同。 NIPA.Less

项目成果

H.Kawasaki: "Effect of Introduced Electric Charge on the Volume Phase Transition of N-lsopropylacrylamide Gels" J.Phys.Chem. 101B. 5089-5093 (1997)

H.Kawasaki：“引入电荷对 N-异丙基丙烯酰胺凝胶体积相变的影响”J.Phys.Chem。

H.Kawasaki: "Effects of the gel size on the volume phase transition of poly(N-isopropylacrylamide)gels : A calerimetric study" Langmuir. (in press). (1998)

H.Kawasaki：“凝胶尺寸对聚（N-异丙基丙烯酰胺）凝胶体积相变的影响：量热研究”Langmuir。

前田 悠: "高分子溶液の散逸構造" 高分子. 46・9. 688-690 (1997)

前田裕：“聚合物溶液的耗散结构”聚合物46・9（1997）。

S.Sasaki: "Volume Phase transition Behavior of NIPA Gels as a Function of the Chemical Potential of Water" Macromolecules. (印刷中).

S.Sasaki：“NIPA 凝胶的体积相变行为作为水化学势的函数”（正在出版）。

S.Sasaki: "Simple theory for volume phase transition of hydrated gels" Phys.Rev.E. 54. 2761-2765 (1996)

S.Sasaki：“水合凝胶体积相变的简单理论”Phys.Rev.E。