Sustainable cardanol-based ionic surfactants

Alkylbenzenes are among the carbon chains most commonly used as a hydrophobic part to develop surfactants. In this paper, the authors present a sustainable alternative using cardanol. Cardanol is obtained by vacuum distillation of cashew nut shell liquid which is a non-edible oil directly extracted from the shell of the cashew nut, the fruit of the cashew tree. Three ionic surfactants based on cardanol were synthesized: a cationic, an anionic and a zwitterionic surfactant. An intermediate was first synthesized by nucleophilic substitution to generate a primary amine. Subsequently, this amine was used to open the cycles of trimethylammoniumglycidyl chloride and 1,3-propanesultone to obtain cationic and anionic surfactants, respectively. And, finally, the obtained cationic and anionic surfactants were coupled with 1,3-propanesultone and trimethylammoniumglycidyl chloride, respectively, to give sulfobetaine surfactants. The surface activity and Krafft temperature were studied as a function of the salt concentration of the synthesized molecules.