THE MECHANISM OF STERICAL STABILIZATION OF FOAMS AND FOAM FILMS WITH ADSORBED LAYERS OF SURFACTANT-POLYELECTROLYTE COMPLEXES

The effect of cationic surfactant (tetradecyltrimethylammoniun bromide , TDTMAB) and anionic polyelectrolyte (carboxymethyl chitin, CMDC) in mixed aqueous solutions on the stability of foams and microscopic foam films (MFF) formed between two air bubbles in an aqueous medium was s tudied. A strong synergistic (nonadditive) effect of studied surfactan ts and polyelectrolyte on the lifetime of foams and MFFs is associated with the formation of nonstoichiometric water-soluble surfactant-poly electrolyte complexes with the composition phi = [surfactant](b)/[poly electrolyte] possessing high adsorption activity at the air-water inte rface. It was shown that with an increase in phi (after the complex ac hieves the critical composition phi = 0.1), surfactant-polyelectrolyt e macromolecules undergo a cooperative transition of a statistical coi l-globule type resulting from hydrophobic interaction between alkyl ra dicals of surfactant molecules bonded with polyelectrolyte. This trans ition leads to the formation of micellelike clusters inside the macrom olecular chain of polyelectrolyte. The mechanism of sterical stabiliza tion of foams and MFFs suggested explaining an increase in their stabi lity with an increase in phi in the range of phi < 0.1 and the indepen dence of the stability of phi at phi > phi = 0.1.