INTERACTION OF SULFONATED POLYSTYRENE WITH CATIONIC SURFACTANTS IN AQUEOUS SOLUTION

Abstract

The interaction of sulfonated polystyrene (SPS) with cetyl trimethylammonium bromide (CTAB) and myristyl trimethylammonium bromide (MTAB) in aqueous solution was investigated. It was found that the solution viscosity increases rapidly at the molar ratio of CTAB/-SO3Na = 0.5 or MTAB/-SO3Na = 0.6 (the first viscosity maximum) and CTAB/-SO3Na = ∼1.5 or MTAB/-SO3Na = 2.0 (the second viscosity maximum). Both the first and the second viscosity maxima are related closely with the hydrophobic domains formed in solution, which can be detected using methyl orange as a spectral probe or N,N-dimethylamino flavone as fluorescent probe. In the higher concentration of [SPS], such as >0.05 M (-SO3Na unit), the SPS/CTAB solution converts to gel suddenly at CTAB/-SO3Na = ∼1.5–1.7 region, but with a further addition of CTAB or SPS, the gel collapses quickly. A term “micelle crosslinking” was proposed to explain the conversion of solution/gel and the reversible nature of gel ↔ solution.