Abstract
Self-consistent field (SCF) calculations and light scattering experiments were performed to study the pH and salt response of micelles composed of surfactants with a single weak acid group in aqueous salt solution. To this end, the common surfactant Brij 35 was oxidized to yield a polyoxyethylene alkyl ether carboxylic acid with a single terminal weakly charged carboxylic acid group in alkaline media. At low pH values, the micellar hydrodynamic radii (Rh) are independent of the salt concentration. By contrast, at pH values around the acid dissociation constant (pH ≈ pKa ± 1), the micellar radius decreases upon increasing pH until a salt-dependent plateau value is reached. The reduction in micellar size is more pronounced for lower salt concentrations. The SCF computations are in qualitative agreement with the experimental results and further reveal a limiting value for Rh corresponding approximately to the Debye length λD. Self-assembly into micelles is suppressed for low salt concentrations that would yield Rh < λD. Instead, the surfactants remain as unimers in solution. The results are summarized in a state diagram displaying the preferred surfactant configuration in solution as a function of Rh/λD, pH and salt concentration.
| Language | English |
|---|---|
| Pages | 201-208 |
| Number of pages | 8 |
| Journal | Colloids and Surfaces A: Physicochemical and Engineering Aspects |
| Volume | 561 |
| DOIs | |
| State | Published - 20 Jan 2019 |
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Keywords
- Model systems
- Self-assembly
- Surfactants
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Micellization of a weakly charged surfactant in aqueous salt solution : self-consistent field theory and experiments. / González García, Álvaro; Timmers, Elizabeth Maria; Romijn, Noah; Song, Shidong; Sahebali, Sheen; Tuinier, Remco (Corresponding author); Voets, Ilja Karina (Corresponding author).
In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, Vol. 561, 20.01.2019, p. 201-208.Research output: Contribution to journal › Article › Academic › peer-review
TY - JOUR
T1 - Micellization of a weakly charged surfactant in aqueous salt solution
T2 - Colloids and Surfaces A: Physicochemical and Engineering Aspects
AU - González García,Álvaro
AU - Timmers,Elizabeth Maria
AU - Romijn,Noah
AU - Song,Shidong
AU - Sahebali,Sheen
AU - Tuinier,Remco
AU - Voets,Ilja Karina
PY - 2019/1/20
Y1 - 2019/1/20
N2 - Self-consistent field (SCF) calculations and light scattering experiments were performed to study the pH and salt response of micelles composed of surfactants with a single weak acid group in aqueous salt solution. To this end, the common surfactant Brij 35 was oxidized to yield a polyoxyethylene alkyl ether carboxylic acid with a single terminal weakly charged carboxylic acid group in alkaline media. At low pH values, the micellar hydrodynamic radii (Rh) are independent of the salt concentration. By contrast, at pH values around the acid dissociation constant (pH ≈ pKa ± 1), the micellar radius decreases upon increasing pH until a salt-dependent plateau value is reached. The reduction in micellar size is more pronounced for lower salt concentrations. The SCF computations are in qualitative agreement with the experimental results and further reveal a limiting value for Rh corresponding approximately to the Debye length λD. Self-assembly into micelles is suppressed for low salt concentrations that would yield Rh < λD. Instead, the surfactants remain as unimers in solution. The results are summarized in a state diagram displaying the preferred surfactant configuration in solution as a function of Rh/λD, pH and salt concentration.
AB - Self-consistent field (SCF) calculations and light scattering experiments were performed to study the pH and salt response of micelles composed of surfactants with a single weak acid group in aqueous salt solution. To this end, the common surfactant Brij 35 was oxidized to yield a polyoxyethylene alkyl ether carboxylic acid with a single terminal weakly charged carboxylic acid group in alkaline media. At low pH values, the micellar hydrodynamic radii (Rh) are independent of the salt concentration. By contrast, at pH values around the acid dissociation constant (pH ≈ pKa ± 1), the micellar radius decreases upon increasing pH until a salt-dependent plateau value is reached. The reduction in micellar size is more pronounced for lower salt concentrations. The SCF computations are in qualitative agreement with the experimental results and further reveal a limiting value for Rh corresponding approximately to the Debye length λD. Self-assembly into micelles is suppressed for low salt concentrations that would yield Rh < λD. Instead, the surfactants remain as unimers in solution. The results are summarized in a state diagram displaying the preferred surfactant configuration in solution as a function of Rh/λD, pH and salt concentration.
KW - Model systems
KW - Self-assembly
KW - Surfactants
UR - http://www.scopus.com/inward/record.url?scp=85055909270&partnerID=8YFLogxK
U2 - 10.1016/j.colsurfa.2018.10.039
DO - 10.1016/j.colsurfa.2018.10.039
M3 - Article
VL - 561
SP - 201
EP - 208
JO - Colloids and Surfaces A: Physicochemical and Engineering Aspects
JF - Colloids and Surfaces A: Physicochemical and Engineering Aspects
SN - 0927-7757
ER -