ANIONIC POLYELECTROLYTE BINDING TO MIXED CATIONIC-ZWITTERIONIC SURFACTANT MICELLES - A MOLECULAR PERSPECTIVE FROM H-2 NMR-SPECTROSCOPY

Complex formation between an anionic polyelectrolyte poly(sodium styre nesulfonate) (PSSS) and mixed zwitterionic-cationic surfactant micelle s was monitored using deuterium NMR spectroscopy of the specifically d euterium-labeled surfactants hexadecylphosphocholine (HDPC-gamma-d(6)) and cetyltrimethylammonium bromide (CTAB-gamma-d(9)). The deuterium s ignal from both surfactants decreased in direct proportion to the amou nt of added PSSS, reflecting the phase separation of the charge-neutra lized PSSS-surfactant complex. The insoluble complex was preferentiall y enriched with CTAB over HDPC. The PSSS/CTAB charge ratio was the pri mary determinant of the degree of complex formation. Deuterium NMR T-1 and T-2 relaxation time measurements indicated that soluble PSSS-surf actant complexes exist prior to their phase separation. Within these s oluble complexes motions of the cationic surfactant CTAB, but not the zwitterionic surfactant HDPC, were hindered. Quadrupolar echo deuteriu m NMR spectra of the phase-separated complexes showed that the floccul ated material is inhomogeneous in composition and that surfactant mobi lity within the insoluble complex varies according to the CTAB/HDPC ra tio.