Spectroscopic Studies on the Competitive Interaction between Polystyrene Sodium Sulfonate with Polycations and the N-Tetradecyl Trimethyl Ammonium Bromide Surfactant

The interaction of N-tetradecyl trimethyl ammonium bromide (TTAB) surfactants with poly(sodium styrene sulfonate) (PSS), PSS/poly(allylamine hydrochloride) (PAH), and PSS/poly(diallyl dimethyl ammonium chloride) (PDADMAC) complexes has been studied by means of Raman and IR spectroscopy. The stoichiometry of the polyelectrolyte complexes and of the complexes with TTAB has been established. TTAB molecules bind to single PSS molecules in a coiled liquid-like alkyl configuration LIP to a molar fraction of 67% in dry state. At higher concentrations, TTAB shows a transition to a crystalline phase. In the case of PSS being complexed with PAH, surfactants binds to PSS with a stoichiometry of 2 molecules of TTAB per sulfonic acid group. Spectroscopic data show that TTAB interacting with PSS/PDADMAC complexes is capable of disassembling this polyelectrolyte complex, but when TTAB interacts with the PSS/PAH complexes this polyelectrolyte pair remains stable. Spectroscopic measurements performed at different humidity showed that dry PSS/PAH complexes display the nu(SO2) and nu(s)(SO3-) bands at positions, which are indicative of the presence of hydrogen bonds between PSS and PAH. Red shifts of these bands when mixing the PSS/PAH complexes with TTAB point to structural rearrangements of the complex when interacting with the surfactant.