Aggregation behavior of amino acid ionic liquid surfactants in aqueous media.
Self-aggregation of amino acid ionic liquid surfactants (AAILSs) in aqueous solution has been investigated through surface tension, conductivity, steady-state fluorescence, dynamic light scattering (DLS), and transmission electron microscopy (TEM). The critical aggregation concentration (cac) of AAILSs obtained from different techniques showed fairly good agreement. Surface tension measurements have been used to derive surface adsorption properties such as adsorption efficiency (pC(20), effectiveness of surface tension reduction (Π(cac)), and minimum surface area per molecule (A(min)) at the air-water interface. Temperature-dependent conductivity measurements have been used to obtain the degree of counterion binding (β), and the thermodynamic parameters such as standard free energy (ΔG(agg)(0)), enthalpy (ΔH(agg)(0)), and entropy (ΔS(agg)(0)) of aggregation. The aggregation number (N(agg)) for various AAILSs has been derived by using the fluorescence quenching technique. Size of the aggregates has been obtained from DLS and TEM measurements. The aggregation properties of AAILSs have been analyzed as a function of structure of amino acids and compared with those of analogous ionic liquids (ILs) and conventional ionic surfactants. Surface activity of the AAILSs has been found superior to that of analogous ILs and conventional ionic surfactants of the same alkyl chain length.
Salt and Marine Chemicals Division, Central Salt and Marine Chemicals Research Institute, Council of Scientific and Industrial Research (CSIR), G. B. Marg, Bhavnagar 364002, India.
K Srinivasa
KS
Rao
Tejwant
T
Singh
Tushar J
TJ
Trivedi
Arvind
A
Kumar
D000596:Amino Acids / Q000737:chemistry*; D004553:Electric Conductivity; D052578:Ionic Liquids / Q000737:chemistry*; D008027:Light; D012542:Scattering, Radiation; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry*; D013696:Temperature; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
D000596:Amino Acids; D052578:Ionic Liquids; D013501:Surface-Active Agents; D014867:Water