Facile synthesis, surface activity, wettability and ultrahigh foaming properties of novel nonionic Gemini fluorocarbon surfactants

Two nonionic Gemini fluorocarbon surfactants containing ecofriendly ester-bonded, named as MN-2C9F19 and EN-2C9F19 were designed and synthesized by one-step esterification. Their surface properties, wettability, thermal properties, and foaming characterization were systematically studied. Two surfactants exhibited high surface activity in aqueous solution, with surface tension (γcmc) of 14.20 mN/m for MN-2C9F19 and 13.71 mN/m for EN-2C9F19. Moreover, MN-2C9F19 and EN-2C9F19 showed high decomposition temperature (Td) of up to 165.4 °C and 176.7 °C respectively. Although the structural difference between methyl and ethyl group is negligible, their wettability and foaming properties are quite different. EN-2C9F19 could wet the low surface energy PTEF plate completely at low concentration (0.6 mM) but MN-2C9F19 needed higher concentration (1.2 mM). Also, EN-2C9F19 exhibited much better foaming property with the foam integrated value F up to 4,370,500 mL·s while MN-2C9F19 could reach up to 2,732,580 mL·s. This maybe ascribe to lower surface tension and higher viscosity of EN-2C9F19 solution. Furthermore, two surfactants showed stronger foaming properties at high temperatures than the conventional foam surfactant SDBS even at room temperature. This work provided an easy synthesis route to develop high-performance foaming agents at high temperatures.