Determination of critical micelle concentration by hyper-rayleigh scattering.
The critical micelle concentration (CMC) of several surfactants that contain an NLO chromophore, either at the hydrocarbon tail, or at the hydrophilic headgroup, or even as a counterion, was determined by hyper-Rayleigh scattering (HRS). In all cases, the HRS signal exhibited a similar variation with surfactant concentration, wherein the CMC is inferred from a rather unprecedented drop in the signal intensity. This drop is attributed to the formation of small pre-micellar aggregates, whose concentrations become negligible above CMC. In addition, a probe molecule, which upon protonation yielded a species with significantly enhanced HRS intensity, was developed and its utility for the determination of the CMC of simple fatty acids was demonstrated.
Ghosh
Suhrit
S
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012, India. raman@ipc.iisc.ernet.in
Krishnan
Anu
A
Das
Puspendu K
PK
Ramakrishnan
S
S