Synthesis and surface activity of two novel phosphate silicone surfactants

Two phosphate amphoteric surfactants based on silicone were synthesized. Phosphate Gemini surfactant ((C12P2)2Si2) with disiloxane as bridging group and double-chain surfactant (C12P2Si3) with hydrophobic hydrocarbon chain and trisiloxane were prepared by hydrolysis reaction, Kabachnik-Fields reaction, and quaternization reaction. FT-IR, 1H NMR and TGA confirmed the chemical structure and thermal stability of the synthesised (C12P2)2Si2 and C12P2Si3. The physicochemical behavior at the air–liquid interface was investigated. The results showed that the critical micelle concentration (CMC) values of (C12P2)2Si2 and C12P2Si3 are 0.53 and 0.78 mmol/L, respectively. The two new surfactants had surface tension at CMC equal to approximately 28 mN/m and their surface tension varied with temperature and electrolyte (NaCl, CaCl2, and MgCl2) concentration. At high temperatures and with high concentration electrolytes, they exhibited good air–liquid interfacial activity. In addition, the size of the aggregates of the surfactants in aqueous solutions above CMC was determined by the dynamic light scattering (DLS) measurements.