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

基本信息

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

项目摘要

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

我们已经研究了将电离基团或亲水基团引入N-异丙基丙烯酰胺（NIPA）凝胶对体积相变的影响。制备了共聚物凝胶NIPA与丙烯酸，搅拌磺酸盐和丙烯酸功能障碍，并检查了其肿胀行为。我们发现，通过引入非常少量的电荷，NIPA凝胶的肿胀行为如NIPA凝胶的肿胀行为完全消失了。但是，电荷的这种效果被添加盐抑制。在NIPA凝胶和共聚物凝胶上也进行了差扫描量热法。对于大尺寸的凝胶，即使凝胶的体积变化与温度是连续的，也可以在过渡温度附近观察到宽阔但清晰的吸热峰。这表明驱动凝胶链的脱水，体积相变是一种吸热反应。对于最小尺寸的凝胶，两个成功的……在过渡温度附近的体积相变的体积过渡时，观察到了更多的吸热峰。可能有两个解释，脱水是降低体积的柔和，或者由于脱水而引起的吸热能量通过某些未知机制的放热能量补偿。我们发现，通过添加盐，降低的反应焓可提高到原始水平。我们已经发现了NIPA和丙烯酸的共聚物凝胶在pH = 2处的新型体积相变，即使后者的月份含量高达10％。发现包括吸热能在内的热行为与NIPA凝胶的热行为相同，除非超高温度低。这表明联合丙烯酸的疏水性与NIPA相同。较少的