Interactions in a nonionic surfactant and chitosan mixtures

Interactions in mixtures of nonionic surfactant, Lutrol F127, and cationic polyelectrolyte, chitosan from water solution and acetate buffer (pH 6.0 or 6.5 and ionic strength 0.1 and 0.5) have been investigated at two different temperatures (25 and 34 °C). Critical aggregation concentration (cac), critical micellization concentration (cmc) and the minimum area of Lutrol F127 molecule at the air/solution interface (a), were determined using the surface tension measurements. The addition of chitosan to Lutrol F127 solutions shifted the cac and cmc to higher values; the effects were more pronounced for the cmc and in acetate buffer. The Lutrol F127 adsorption at the air/solution interface strongly depended on the equilibria in the bulk-phase, i.e. on the extent of the protonation of chitosan amino groups. The results were discussed in terms of electrostatic, hydrophobic and intra- and inter-polymer interactions.