Counteranion-Specific Hydration States of Cationic Polyelectrolyte Brushes

Yuji Higaki, Yoshihiro Inutsuka, Hitomi Ono, Norifumi L. Yamada, Yuka Ikemoto, Atsushi Takahara

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)


While polyelectrolyte brushes have received extensive attention due to their particular surface properties, the ion-specific hydration states remain largely unknown. Here, we report the counteranion-specific hydration states of cationic poly[2-(methacryloyloxy)ethyltrimethylammonium] (PMTA) brushes in salt-free water. The water droplet contact angle on the PMTA brushes depends on the counteranion species, and the order is consistent with the Hofmeister series. Weakly hydrated chaotropic counteranions are strongly bound to weakly hydrated quaternary ammonium (QA+) cations in the PMTA brush chains, which induces a reduction in the ζ-potential, dehydration, and collapse of the PMTA brushes. The PMTA brushes with strongly hydrated chloride counteranions produce a more diffuse tail and less swollen bound layer under salt-free deuterium oxide than brushes with weakly hydrated thiocyanate counteranions. Ion pairing disturbs the ordering of hydrated water in the PMTA brushes. Our work enhances the understanding of the ion specificity in the hydration states of polyelectrolyte brushes and encourages the rational design of charged polymer materials.

Original languageEnglish
Pages (from-to)5268-5275
Number of pages8
JournalIndustrial and Engineering Chemistry Research
Issue number15
Publication statusPublished - Apr 18 2018

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Chemical Engineering(all)
  • Industrial and Manufacturing Engineering


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