Effects of Non-Ionic Micelles on the Acid-Base Equilibria of a Weak Polyelectrolyte

Evgenee Yekymov, David Attia, Yael Levi-Kalisman, Ronit Bitton, Rachel Yerushalmi-Rozen*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Weak polyelectrolytes (WPEs) are widely used as pH-responsive materials, pH modulators and charge regulators in biomedical and technological applications that involve multi-component fluid environments. In these complex fluids, coupling between (often weak) interactions induced by micelles, nanoparticles and molecular aggregates modify the pKa as compared to that measured in single component solutions. Here we investigated the effect of coupling between hydrogen bonding and excluded volume interactions on the titration curves and pKa of polyacrylic acid (PAA) in solutions comprising PEO-based micelles (Pluronics and Brij-S20) of different size and volume fraction. Titration experiments of dilute, salt-free solutions of PAA (5 kDa, 30 kDa and 100 kDa) at low degree of polymer ionization (α < 0.25) drive spatial re-organization of the system, reduce the degree of ionization and consequentially increase the pKa by up to ~0.7 units. These findings indicate that the actual degree of ionization of WPEs measured in complex fluids is significantly lower (at a given pH) than that measured in single-component solutions.

Original languageAmerican English
Article number1926
Issue number9
StatePublished - 1 May 2022

Bibliographical note

Publisher Copyright:
© 2022 by the authors. Licensee MDPI, Basel, Switzerland.


  • Brij-S20
  • F108
  • F127
  • PAA
  • WPEs
  • acid base
  • equilibrium
  • excluded volume
  • pH
  • pKa
  • polyacrylic acid
  • surfactant
  • weak polyelectrolytes


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