Thermodynamics of Interaction between Cationic Gemini Surfactants and Hydrophobically Modified Polymers in Aqueous Solutions

Abstract

Microcalorimetry has been used to study the interactions between two gemini surfactants, [C12H25(CH3)2N(CH2)SN(CH3)2C12H25]Br2, with S = 3 and 6, and several modified poly(acrylamides) (PAM) including hydrophobic groups and acrylic acid residues. Values of enthalpies, entropies, and free energies of interaction have been derived for the two gemini surfactants and two single-chain surfactants, sodium dodecyl sulfate and dodecyltrimethylammonium bromide. The interaction with the polymers was found to be much stronger for the geminis in comparison with the single-chain surfactants and was also found to be strongly dependent on the spacer length. Inclusion of acrylic acid residues in hydrophobically modified PAMs generates a strong specific interaction between polymer and gemini surfactant that acts to disrupt the aggregation of the surfactant.