Effect of surfactant hydrophobicity on the interfacial properties of polyallylamine hydrochloride/sodium alkylsulphate at water/hexane interface

The bulk, interfacial and emulsion (water/hexane interface) properties of mixtures of the cationic polyelectrolyte polyallylamine hydrochloride (PAH) and anionic surfactants sodium alkyl sulphates with different alkyl chain length from C10 to C16 are studied via zeta potential (ζ), dynamic light scattering, interfacial tension and dilational rheology measurements. It was established that with increasing surfactant’s alkyl chain length the interfacial tension of mixtures with the polymer decreases as expected while ζ-potentials change remarkably when passing from C12 to C14. Based on the hydrodynamic radii of the formed complexes it can be concluded that for SDS the most dense compact statistical coils of polycomplexes are formed due to both electrostatic and hydrophobic interactions. The large hydrodynamic radii of the PAH/STS and PAH/SHS polycomplexes indicate the formation of bulky swollen associates. The difference in the structure of the polycomplexes changing from dense dispersed particles to bulky associates, at large radicals can effect to the strength and the physical and mechanical characteristic parameters of the interfacial adsorption layers and determines the stability of corresponding emulsion films.