SYNTHESIS AND PROPERTIES OF ZWITTERIONIC SURFACTANTS

Structure - properties relationships are systematically investigated on zwitterionic surfactants at interfaces. Our methodology is based on a comparison of properties over series of homologuous surfactants. The respective influences of various molecular parameters can then be deduced. Such series of compounds are available from organic synthesis which can involve some interesting chemical reactions from the organic chemist point of view. This is illustrated with two examples. Simple surface tension measurements allow to study the main thermodynamic and structural effects. Complementary micellar size measurements show the influence of parameters as measured at the air-water interface on the interfacial curvature. The influence of the dipole moment beared by the zwitterionic polar part is thus demonstrated by this way. Other important molecular parameters in the polar heads are their size, the hydrophobic character and the flexibility of the spacer linking the two charges of the zwitterion.