Surface Activity, Spreading, and Aggregation Behavior of Ecofriendly Perfluoropolyether Amide Propyl Betaine in Aqueous Solution

The hydrophobic–oleophobic properties of perfluoropolyether (PFPE) are similar to those of fluorocarbons with seven or more long carbon chains, and it’s biodegradable properties make it a good alternative to conventional perfluorooctyl derivatives. In this study, a novel environmentally friendly fluorinated surfactant perfluoropolyether amide propyl betaine (PFPE-B) was synthesized and characterized by Fourier transform infrared spectroscopy and 1H and and 19F NMR. Its surface activity, micellization, and adsorption performance at the gas–liquid interface and wettability and aggregation behavior in aqueous solution were systematically investigated by surface tension, electrical conductivity, dynamic surface tension, dynamic contact angle, dynamic light scattering (DLS), and transmission electron microscopy (TEM) techniques. The γcmc and critical micelle concentration (CMC) value for PFPE-B are about 16.87 mN·m–1 and 0.07 mmol·L–1, far less than that of cocoamidopropyl betaine (CAB), demonstrating that surfactant PFPE-B has higher surface activity than surfactants with a hydrocarbon chain. And, it was confirmed that the kinetics of adsorption at the interface increases with an increase of concentration. Contact angle measurements conducted on low-energy paraffin film and polytetrafluoroethylene surfaces demonstrated that PFPE-B exhibited efficient spreading above the CMC. Furthermore, DLS and TEM studies revealed that PFPE-B self-assembled in aqueous solution to form spherical vesicles.