Salt effect on complex formation of neutral/polyelectrolyte block copolymers and oppositely charged surfactants

Tsuyoshi Matsuda, Masahiko Annaka

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

The salt effect on the complex formation of poly(acrylamide)-block- poly(sodium acrylate) (PAM-b-PAA) as a neutral-anionic block copolymer and dodecyltrimethylammonium bromide (DTAB) as a cationic surfactant at different NaBr concentrations, CNaBr, was investigated by turbidimetric titration, steady-state fluorescence spectroscopy, and dynamic light scattering. At CNaBr < 0.25 M, DTAB molecules may form micelle-like aggregates on PAM-b-PAA chains to form a PAM-b-PAA/DTAB complex above the critical surfactant concentration Ccritical for the onset of complex formation. In the region of relatively high turbidity, a larger complex is likely to form a core-shell structure, of which the core is a dense and disordered microphase made of surfactant micelles connected by the PAA blocks. The corona was a diffuse shell of PAM chains, and it ensured steric stability. At CNaBr= 0.25 M, a higher electrostatic intermicellar repulsion and intercomplex repulsion induced by a large amount of bound DTAB micelles may lead to a redissolution of large colloidal complexes into intrapolymer complexes. Moreover, a salt-enhancing effect on the complex formation was observed in the PAM-b-PAA/DTAB system; the critical surfactant concentration decreased with increasing salt concentration at CNaBr < 0.10 M. The salt-enhancing effect is due to the larger increase of interaction in comparison to the screening of the interaction.

Original languageEnglish
Pages (from-to)5707-5713
Number of pages7
JournalLangmuir
Volume24
Issue number11
DOIs
Publication statusPublished - Jun 3 2008

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carbopol 940
Polyacrylates
Polyelectrolytes
block copolymers
Surface-Active Agents
Block copolymers
bromides
acrylates
Surface active agents
Salts
surfactants
Sodium
Micelles
salts
sodium
micelles
Pulse amplitude modulation
Cationic surfactants
pulse amplitude modulation
Fluorescence spectroscopy

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

Cite this

Salt effect on complex formation of neutral/polyelectrolyte block copolymers and oppositely charged surfactants. / Matsuda, Tsuyoshi; Annaka, Masahiko.

In: Langmuir, Vol. 24, No. 11, 03.06.2008, p. 5707-5713.

Research output: Contribution to journalArticle

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