Tuning the structure of surfactant complexes with DNA and other polyelectrolytes
Raman Research Institute, Bangalore 560 080, India
2 Department of Physics, Indian Institute of Science - Bangalore 560 012, India
Accepted: 7 March 2003
We have carried out small-angle X-ray diffraction studies on complexes formed by the anionic polyelectrolytes, namely, sodium salts of double and single stranded (ds and ss) DNA, poly(glutamic acid) (PGA), poly(acrylic acid) (PAA), and poly(styrene sulfonate) (PSS) with a cationic surfactant system consisting of cetyltrimethylammonium bromide (CTAB) and sodium 3-hydroxy-2-naphthoate (SHN). All complexes have a two-dimensional (2D) hexagonal structure at low SHN concentrations. DNA-CTAB-SHN complexes exhibit a hexagonal to lamellar transition near the SHN concentration at which CTAB-SHN micelles show a cylinder to bilayer transformation. On the other hand, PGA and PAA complexes form a 2D centered rectangular phase at higher SHN concentrations, and PSS complexes show a primitive rectangular structure. These results provide a striking example of polyion specificity in polyelectrolyte-surfactant interactions.
PACS: 61.30.Eb – Experimental determinations of smectic, nematic, cholesteric, and other structures / 61.10.Eq – X-ray scattering (including small-angle scattering) / 87.15.By – Structure and bonding
© EDP Sciences, 2003