Salt effect on complex formation of neutral/polyelectrolyte block copolymers and oppositely charged surfactants
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, stead...
| Veröffentlicht in: | Langmuir : the ACS journal of surfaces and colloids. - 1992. - 24(2008), 11 vom: 03. Juni, Seite 5707-13 |
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| Format: | Online-Aufsatz |
| Sprache: | English |
| Veröffentlicht: |
2008
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| Zugriff auf das übergeordnete Werk: | Langmuir : the ACS journal of surfaces and colloids |
| Schlagworte: | Journal Article |
| Zusammenfassung: | 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 C NaBr < 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 C critical 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 |
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| Beschreibung: | Date Completed 22.07.2008 Date Revised 28.05.2008 published: Print-Electronic Citation Status PubMed-not-MEDLINE |
| ISSN: | 1520-5827 |
| DOI: | 10.1021/la704054h |