Ionization of short weak polyelectrolytes: when size matters

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• 作者：Caterina Dolce ; Guillaume Mériguet
• 关键词：Polyelectrolytes ; Spectroscopy ; Magnetic resonance ; NMR/ESR ; Diffusion ; Sodium polyacrylate
• 刊名：Colloid and Polymer Science
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：295
• 期：2
• 页码：279-287
• 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

The ionization of short weak polyelectrolytes in dilute solutions is investigated by 1H nuclear magnetic resonance (NMR). The increase of the pH of the medium causes both the ionization of the polyacids and, due to the intra-molecular repulsions, the swelling of the chains. As a result, a noticeable effect of the pH change on the NMR chemical shift δ, and on the self-diffusion coefficient D is observed. The ionization of the polyelectrolyte occurs at higher pH as the length of the chain increases. The variation of the self-diffusion coefficient with pH exhibits the opposite dependence on the length of the chain. However, no detectable effect of the length of the polyelectrolyte chain on the evolution of the chemical shift with pH is observed. These apparent contradictions are examined to clarify the impact of the chain length on the polyelectrolyte properties, and the counterion role in the ionization process.