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

Research output: Contribution to journalArticlepeer-review

Abstract

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 languageEnglish
Article number1926
JournalPolymers
Volume14
Issue number9
DOIs
StatePublished - 1 May 2022

Keywords

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

ASJC Scopus subject areas

  • Chemistry (all)
  • Polymers and Plastics

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