Zeta potential of PNIPAM microgel particles dispersed in water—effects of charged radical initiators vs. OH⁻ ion adsorption

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• 作者：Yuka Utashiro ; Mizuki Takiguchi ; Mitsuru Satoh
• 关键词：PNIPAM ; Zeta potential ; Microgels ; Radical initiators ; OH− adsorption
• 刊名：Colloid and Polymer Science
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：295
• 期：1
• 页码：45-52
• 全文大小：
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Polymer Sciences; Soft and Granular Matter, Complex Fluids and Microfluidics; Characterization and Evaluation of Materials; Physical Chemistry; Food Science; Nanotechnology and Microengineering;
• 出版者：Springer Berlin Heidelberg
• ISSN：1435-1536
• 卷排序：295

文摘

It has been known that zeta potential (ζ) or electrophoretic mobility of poly(N-isopropyl acrylamide) (PNIPAM) gel particles in water significantly increase in the magnitude with increasing the temperature. This phenomenon has been interpreted as caused by an enhancement of the surface charge density, which was derived from charged initiator used for the gel preparation, due to the temperature-induced gel deswelling. On the other hand, it has also been established that oil droplets dispersed in water show a negative ζ, which has been ascribed to a specific adsorption of OH− ions from aqueous phase to the hydrophobic hydration layer around the nonpolar droplets. In the present study, we attempted to see if the OH− adsorption actually contributes toζ of PNIPAM microgel particles prepared with four kinds of radical initiators including neutral one. ζ measurements were carried out to find that not only the neutral gel particles but also weakly cationic ones showed a significantly negativeζ at the higher temperature region where the gel collapse occurred. ζ values in the presence of 10−4 M NaCl, NaOH, or HCl were also measured and proved to be consistent with the OH− ion adsorption mechanism.