8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Fri 911:10-14:00P3.23Lysine based surfactants: relationship between chemicalstructure and adsorption/aggregation propertiesRamon Pons, 1 Aurora Colomer, 1 Lourdes Pérez, 1 Aurora Pinazo, 1 and Maria-RosaInfante 11 IQAC-CSIC, Jordi Girona 18-26, 08034, Barcelona, SpainThe economic importance of cationic surfactants was realized early in 1935, when their bacteriostaticproperties were discovered, leading to many commercial products as sanitizing and antisepticagents, germicides, fungicides, and as components in pharmaceutical and cosmetic formulations.In these latter applications adverse effects may occur causing eye and skin irritation. Thereforeit is paramount to develop new surfactants with low toxicity profiles. During the last 20 years,our group has been developing new biocompatible surfactants derived from amino acids. Amongthem, Lysine derivative surfactants constitute a novel class that can be regarded as an alternativeto conventional cationic surfactants. This work reports on the relationship between the structureand adsorption/aggregation properties of ten Lysine-based surfactants including surfactants withone single chain and gemini surfactants. The critical micellar concentration was determined usingconductivity and ionic activity (Cl − and H + ). The cmc for single chain surfactants are of thesame order of magnitude than commercial cationic surfactants. Concerning gemini surfactants,cmc are one order of magnitude smaller than those of single chain surfactants. The phase behaviorat medium to high concentration has been studied by Optical polarizing microscopy, DifferentialScanning Calorimetry and Small Angle X-Ray Scattering. The results will be discussed in termsof the structure of the compounds and the position of the cationic charge on the molecule. We willshow how, apparently small changes in molecule structure have large influence in phase behaviour.23