TY - JOUR
T1 - Effective charge of PNIPAM microgels determined by conductivity measurements
AU - Campos-Ramírez, Adriana
AU - Lozano-Martínez, Antelmo
AU - Ledesma-Motolinía, Mónica
AU - Rojas-Ochoa, Luis Fernando
AU - Haro-Pérez, Catalina
N1 - Publisher Copyright:
© 2023 The Authors. Journal of Polymer Science published by Wiley Periodicals LLC.
PY - 2023/9/15
Y1 - 2023/9/15
N2 - 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.
AB - 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.
KW - PNIPAM
KW - charged microgels
KW - conductivity
KW - effective charge
KW - thermosensitive polymers
UR - http://www.scopus.com/inward/record.url?scp=85159913757&partnerID=8YFLogxK
U2 - 10.1002/pol.20230083
DO - 10.1002/pol.20230083
M3 - Artículo
AN - SCOPUS:85159913757
SN - 2642-4150
VL - 61
SP - 2115
EP - 2121
JO - Journal of Polymer Science
JF - Journal of Polymer Science
IS - 18
ER -