| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 608603 | Journal of Colloid and Interface Science | 2011 | 8 Pages |
The micellization of cationic gemini surfactant trimethylene-1,3-bis (dodecyldimethylammonium bromide) (12-3-12·2Br) was investigated and critical micelle concentrations (CMC) and thermodynamic parameters were evaluated as functions of ionic strength and temperature. The micellization of 12-3-12·2Br is entropically driven and thermodynamically favored. Raising the temperature slightly increases the CMC, while increasing the ionic strength lowers the CMC. A multi-technique study of the 12-3-12·2Br/DNA interaction and its dependence on ionic strength, temperature and DNA concentration were presented. DNA with loose coil conformation, necklace-like structure, highly ordered toroidal aggregates and coexisting of large aggregates and small structures in DNA/12-3-12·2Br system were observed. Critical aggregation concentrations (CAC), interaction saturation concentrations (C2), and associated thermodynamic parameters were determined. The screening effect of salt decreases the DNA/12-3-12·2Br electrostatic attraction, but favors the formation of free 12-3-12·2Br micelles or aggregates on the DNA chain. DNA acts as a separate phase contacting with the surfactant molecules and therefore CAC is independent of DNA concentration. Increasing DNA concentration postpones the appearance of free micelle in bulk phase, consequently increases the C2. Finally an interaction mechanism between 12-3-12·2Br and DNA was proposed.
Graphical abstractComplex formation occurs at CAC, indicated by decrease of transmittance and ΔHobs. After C2, 12-3-12·2Br/DNA interactions reach saturation and free micelles emerge.Figure optionsDownload full-size imageDownload high-quality image (54 K)Download as PowerPoint slideHighlights► The micellization of 12-3-12·2Br is entropically driven and thermodynamically favored. ► Salt screens DNA/12-3-12·2Br electrostatic action but favors surfactant aggregation. ► DNA behaves as a separate phase so that the CAC is independent of DNA concentration.
