Reversible flocculation of nanoparticles by a carbamate surfactant
Journal article, 2019

Fatty alkyldiamine readily reacts with CO2 in aqueous solution at pH 12 to reversibly form surface active carbamate species. The carbamate can be reverted to the amine by exposure to N2 and heat. In this work, a carbamate-based surfactant (Y12-carbamate) has been used to disperse and stabilize hydrophobic nanoparticles. This state could be regarded as the “on” state of a series of cycle. The nanoparticles were then flocculated when the carbamate groups were cleaved by exposure to N2 and heating, corresponding to the “off” state. In a subsequent cycle, the nanoparticles were re-dispersed by exposure to CO2, while the pH remained at 12. This cycle of re-dispersion and flocculation could be repeated two times without impairing the particle size. However, further cycles increased the particle size, indicating that all particles could not be completely re-dispersed. In addition, we also investigated the effect of pH on the colloidal stability with sodium Y12-carbamate, by measuring particle size and electrophoretic mobility. The results showed that pH strongly influenced the stability of the nanoparticles. Sodium Y12-carbamate stabilized the particles with a negative electrophoretic mobility at pH well above pKa whereas at pH close to pKa of Y12-amine (pKa = 9.0), the particles quickly flocculated, as a result of an ion-pair formation between Y12-ammonium and Y12-carbamate.

Colloidal stability

Aggregation

Stimuli-responsive surfactant

Carbamate surfactant

Author

Anna-Karin Hellström

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry

Romain Bordes

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry

Journal of Colloid and Interface Science

0021-9797 (ISSN)

Vol. 536 722-727

Subject Categories

Physical Chemistry

Materials Chemistry

Other Chemistry Topics

DOI

10.1016/j.jcis.2018.10.057

More information

Latest update

11/21/2018