PERFLUOROPOLYETHERS WITH ACID END-GROUPS - AMPHIPHILICITY AND EMULSIFICATION

Interactions of PFPE-acids (perfluoropolyethers with carboxylic end groups) with a metal oxide surface and with aqueous systems were examined. The study revealed that (1) PFPE-acids are preferentially adsorbed on metal oxide (ZrO2) surfaces over PFPE of nonfunctionalized form, (2) PFPE-acids of shorter chain length are preferentially adsorbed over PFPE-acids of longer dimension, and (3) the low molecular weight fraction (MW = 1300) of Demnum-SH is abundant in molecular chains terminated with the acid end group at both ends. The study also revealed that PFPE-acids, if agitated with aqueous solution of electrolyte, form an extremely stable macroemulsion of the water-in-oil type. The emulsion is extremely viscoelastic and may contain 50% by weight (hence, 65% by volume) of water. Water is occluded as droplets of diameter of 1-100 microns. A mechanism exists whereby aqueous protons are transported between droplets with the transfer rate greater than or equal to 50 Hz at room temperature. Relevance of these observations in the lubricant application of PFPEs in magnetic recording media is discussed. (C) 1995 John Wiley and Sons, Inc.