Effective charge of PNIPAM microgels determined by conductivity measurements

IF 2.702 Q1 Materials Science
Adriana Campos-Ramírez, Antelmo Lozano-Martínez, Mónica Ledesma-Motolinía, Luis Fernando Rojas-Ochoa, Catalina Haro-Pérez
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引用次数: 0

Abstract

Understanding the effective charge of colloidal particles is crucial to control the stability and performance of a colloidal system. In particular, the electrostatic interaction potential between the particles determines the stability and thermodynamic properties of electrostatically charged colloidal dispersions. In the case of thermosensitive microgels, which are solvent and ions permeable particles, it is expected that the microgel's size and the number of ions within it are affected by temperature changes. This temperature-dependent microgel-solvent ion interchange regulates the microgel net charge and, consequently, the interaction potential. Here, a straightforward experimental method based on conductivity measurements is presented to determine the temperature dependence of the effective net charge of poly-N-isopropylacrylamide, PNIPAM, microgels under different salinity conditions. Our results show that the net charge of the microgel decreases with increasing temperature. Specifically, microgels reduce their net charge by around 40%, when the temperature is changed from 25 to 40 °C. This scenario could be explained by the entrance of counterions into the microgel after its collapse to partially neutralize the increase of the electrostatic repulsion due to the closer proximity among the charged groups present in the polymer particle.

Abstract Image

通过电导率测量确定PNIPAM微凝胶的有效电荷
了解胶体粒子的有效电荷对于控制胶体系统的稳定性和性能至关重要。特别是,粒子之间的静电相互作用势决定了静电带电胶体分散体的稳定性和热力学性质。对于热敏性微凝胶来说,它是溶剂和离子可渗透的颗粒,预计微凝胶的大小和其中的离子数量会受到温度变化的影响。这种温度依赖性的微凝胶-溶剂离子交换调节了微凝胶的净电荷,从而调节了相互作用电位。本文提出了一种基于电导率测量的简单实验方法,以确定不同盐度条件下聚n -异丙基丙烯酰胺(PNIPAM)微凝胶的有效净电荷对温度的依赖关系。结果表明,微凝胶的净电荷随温度的升高而降低。具体来说,当温度从25°C变化到40°C时,微凝胶可以减少约40%的净电荷。这种情况可以解释为,在微凝胶崩溃后,反离子进入微凝胶,以部分中和由于聚合物颗粒中带电基团之间的距离更近而增加的静电斥力。
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来源期刊
CiteScore
5.20
自引率
0.00%
发文量
0
审稿时长
1.8 months
期刊介绍: Part A: Polymer Chemistry is devoted to studies in fundamental organic polymer chemistry and physical organic chemistry. This includes all related topics (such as organic, bioorganic, bioinorganic and biological chemistry of monomers, polymers, oligomers and model compounds, inorganic and organometallic chemistry for catalysts, mechanistic studies, supramolecular chemistry aspects relevant to polymer...
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