SANS studies on conventional and gemini surfactants with and without additives: past, present and future

Solution behaviour of surfactants can be changed by the addition of different additives or by changing experimental conditions. Alkyl amine, quaternary ammonium salts and counter charged amphiphiles have been used to modify micellar morphologies and SANS data were analysed to get micellar parameters and structural information. During above studies, few surfactant systems gave closed bilayer morphologies at certain composition (mole fraction x=0.4 or 0.6). Compositional variation may modify micellar environment as studied by fluorescence measurements. Length of hydrocarbon chain or nature of spacer (in a typical gemini surfactant) shown contribution towards vesicle formation. Among all surfactant assemblies, vesicles are of utmost importance because they are widely used as model bio membranes, nano-container for drug delivery and for nanotechnology. Deep Eutectic solvents (DESs) are greener liquid systems which can be used as association medium for surfactants. Water based DES are finding importance as they can be used with variety of conventional and gemini surfactants. However, morphological information are missing with surfactant + DES systems, therefore, can be studied in future with the SANS spectrometer. (author)