Abstract
The adsorption behavior of N-dodecyl-N,N dimethyl aminobetaine chlorohydrate (DDAB·HCl) at the air/aqueous interface was studied for solutions in pure water and phosphate buffer (pH=7.4). The equilibrium surface tension versus concentration curves were used to estimate the equilibrium adsorption parameters and CMCs. The buffer solution has a lower CMC and shows higher surface activity below the CMC than the pure water solution. Data and calculations of the dynamic tension behavior at constant-area conditions showed that the adsorption processes of DDAB·HCl solutions are about 10 to 300 times slower than those predicted by a diffusion-controlled model. A mixed kinetics adsorption model with a modified Langmuir-Hinshelwood kinetic equation, which considers an activation energy barrier for adsorption, was applied to find the kinetic adsorption parameters. The dynamic tension behavior at pulsating-area conditions with large amplitude was also examined for frequencies up to 90 cycles/min. The tension amplitude responses depended strongly on the concentration and frequency. Comparisons of diffusion-controlled model predictions and pulsating area tension data confirmed the need to use a mixed kinetics model. The latter model can improve the fit over the diffusion-controlled model, but it does not quantitatively match the observed tensions.
Original language | English |
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Pages (from-to) | 447-455 |
Number of pages | 9 |
Journal | Colloid & Polymer Science |
Volume | 272 |
Issue number | 4 |
DOIs | |
Publication status | Published - 1994 Apr 1 |
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Polymers and Plastics
- Colloid and Surface Chemistry
- Materials Chemistry