Study On Synthesis And Properties Of Oxa-perfluoroalkyl End-Capped PEG-based Fluorocarbon Surfactants

Fluorocarbon surfactants were widely applied in various industry fields due to their high surface activity, high thermal stability and chemical stability and excellent hydrophobic, oleophobic properties. However, more and more researchers reported that the fluorocarbon surfactants which were composed of perfluoroheptanecarboxylic acid and perfluorooctane sulfonates and their derivate were toxic to human and environment. So the development of"environment friendly"fluorocarbon surfactants becomes more and more urgent. Therefore, we applied 2-(heptafluoropropoxy)- tetrafluoropropionyl fluoride, 2,5-bis-(trifluoromethyl)-3,6-dioxaundeca- fluorononanoyl fluoride and polyethylene glycol(PEG) as materials, instead of the common used perfluorooctane chains to prepared a serious of oxy-perfluoroalkylated end-capped PEG-based fluorocarbon surfactants. They were 0.4KPEGF2, 0.4KPEGF3, 0.6KPEGF2, 0.6KPEGF3, 1KPEGF2, 1KPEGF3, 2KPEGF2 and 2KPEGF3 (the superscript preceding PEG indicated the molecular weight of polyethylene glycol and the superscript following PEG indicated the fluorinated parts, specifically F2 is 2-(heptafluoropropoxy)- tetra-fluoropropionyl fluoride, and F3 is 2,5-bis(trifluoromethyl)-3,6- dioxaundecafluorononanoyl fluoride).After purification, the structures of products were confirmed by FTIR, NMR and so on, respectively. Their surface activity, cloud point, thermal stability and chemical stability were carefully measured. The results indicate that all these fluoropolymer have extremely high surface activity and amazing chemical stability. For example, 0.4KPEGF3 can reduce the surface tension of water solution from 72.8 mN/m to 12.5mN/m, whose CMC was as low as 0.2mg/ml. The influence of the length of hydrocarbon chain and fluorocarbon chain on the surface properties was explained according to the experiment results. When the samples have same fluorocarbon chain, the surface tension increased as the increase of the length of hydrocarbon chain, so their surface activity decreased. Similarly, when the samples have same hydrocarbon chain, the surface activity becomes better as the length of fluorocarbon chain increase. In addition, the adsorption properties of obtained fluorocarbon surfactants were evaluated by curve fitting method. The obtained fluorocarbon surfactants could be applied as substitute of perfluorooctane derivate in wetting agent, flatting agent, foaming agent and antifouling agent due to their outstanding surface properties.