Effect of Hydrophilic Function Groups on the Properties of Short-Chain Fluorocarbon Surfactants

Short-chain fluorocarbon surfactants grafted with alcohol, carboxyl and ester functional groups were prepared by quaternization with short-chain perfluorobutyl sulfonyl fluoride as raw material. The structures of surfactants were characterized by infrared spectroscopy, nuclear magnetic resonance and mass spectrum. The surface activity, micelle formation process and micelle aggregation behavior of surfactants were studied by surface tensiometer, dynamic light scattering particle size analyzer and fluorescent spectrophotometer. The results show that the critical micelle concentration (CMC) of surfactants are 19.3, 7.8 and 2.2 mmol L-1, and the surface tension of the surfactant solution at CMC are as low as 17.3, 19.2 and 18.5 mN m-1, respectively. The standard Gibbs free energy ( Delta Gm0 ${\Delta G_{\rm{m}}<^>0 }$ ) values of surfactants are negative, and the absolute values of Delta Gm0 ${\Delta G_{\rm{m}}<^>0 }$ are less than the standard Gibbs adsorption energy ( Delta Ga0 ${\Delta G_{\rm{a}}<^>{\rm{0}} }$ ), illustrating that the adsorption process is easier than the micelle formation process. In addition, the size distribution of the aggregates is much larger than that of spherical micelles, showing that the surfactant self-assembled into larger aggregates in solution. The grafted hydrophilic functional groups show a significant effect on the performance of surfactants. The ester-based surfactant has a lower CMC value, which has the advantages of small dosage, good economy and excellent application value. This work synthesizes a series of short-chain fluorocarbon surfactants with different functional groups. The results show that SFCS3 is a single-head and double-tail surfactant, which is conducive enhancing the micelle formation in solution. The CMC and gamma CMC of SFCS3 is 2.2 mmol L-1 and 18.5 mN m-1 respectively, which has the advantages of small dosage, good economy and excellent application value. image