Formation of Perfluorocarbon Microemulsion by Fluorinated Polyethylene Glycol

Perfluorocarbons (PFCs) are chemically and biologically inert, highly gas‐dissolving, highly fluidic, and with low surface tension. Their unique properties have triggered various applications of these compounds in the areas such as oxygen delivery, liquid ventilation, diagnosis, and lubrication. However, PFCs are immiscible with aqueous media, hence surfactants are required to make PFCs as PFC‐in‐water or water‐in‐PFC microemulsions for practical application. In order to overcome this obstacle, one approach should be beneficial to create a PFC microemulsion system with the aid of fluorosurfactants which can drive the interfacial tension of PFC with water to a very low value. In this study, the fluorophilic moiety of fluorosurfactant is an end‐functional perfluorocarbon group (R_F). Methoxy polyethylene glycol (MPEG) was selected as the hydrophilic moiety due to its unique characteristics for versatile application. A series of high yield perfluoroalkylated MPEG surfactants were synthesized by reacting different MW of perfluoroacid chlorides (C_nF_2n+1COCl) with various low MW of amino‐MPEG by amide linkage. According to the ratios of hydrophilic to fluorophilic groups balance (HFB) for these PFC microemulsions obtained, an empirical formula was applied to calculate the HFB value which can be used to design the structure of fluorosurfactant for the preparation of PFC microemulsions. Two different types of PFC liquids, perfluorooctyl bromide (PFOB) and perfluoropolyether (PFPE), were examined for the formation of PFC microemulsions. Our results indicated that the domain of PFC microemulsion was strongly affected by not only the ratio of R_F chain length to MPEG chain length of the fluorosurfactant used but also the type of PFC studied.