Surface properties of new catanionic semi-fluorinated hybrid surfactants

In order to study their aggregation behaviour, a rapid synthetic procedure from perfluoroalkylethyl thiol derivatives led to twenty four original catanionic hybrid surfactants of general formula: [RF(CH2)2S(CHQ)2CO2−; HN+(CH3)2RH (Q = H or Cl; RF = C4F9, C6F13, C8F17; RH = C6H13, C8H17, C10H21, C12H25)]. Critical aggregation concentration (CAC), surface tension at the CAC (γS) and free energy of aggregation ( Δ G A ° ) of the title surfactants, in aqueous solution, have been investigated as a function of the number of carbon atoms in both the fluorinated and the hydrocarbon tails. TEM studies were used to estimate the shape and size of the aggregates and confirmed the general tendency of fluorinated surfactants to form aggregates with lesser curvature. These catanionic surfactants exhibited very low surface tension at critical aggregation concentration (CAC) of 15.3–17.4 mN m−1 as well as low CAC of 3 × 10−5–11 × 10−3 and the substitution of one hydrogen atom by one chlorine atom didn’t affect significantly the aggregation phenomenon.