Perfluoropoly(ethers): Intramolecular disproportionation II

It was shown earlier that perfluoropoly(ethers) (PFPEs) have a propensity t o undergo the intramolecular disproportionation reaction of the following s cheme: [GRAPHICS] The reaction is catalyzed by Lewis acid sites (e.g., Al2O3 or AlCl3) and oc curs at sectors where the successive ether oxygens have an odd number of ba ckbone carbons between them. When the number of such backbone carbons is ev en, the reaction occurs exclusively at chain ends. We examined, in order to further substantiate the parity rule (the even and odd number of carbons b etween successive ether oxygens), the degradation of two novel PFPE's, perf luoropoly(tetramethylene oxide) and perfluoropoly(dioxolane). Both were fou nd to degrade in accordance with the parity rule. It was also shown earlier that the degradation of Fomblin Z (a linear, random copolymer of -CF2-O- a nd -CF2-CF2-O- units) in the presence of Al2O3 was preceded by an induction period. We examined the process that occurs during the induction period. T he study revealed that, during the induction period, the disproportionation reaction occurs exclusively at sectors where three or more acetal units, - CF2-O-, are linked contiguously, and converts surface aluminum oxide to flu oride in the process. Lastly, an examination of PFPE/AlCl3 mixtures by IR s pectroscopy revealed that the disproportionation reaction could commence ev en at room temperature. It is envisaged that, in magnetic recording files, defect centers of a varying degree of acid strength are incessantly generat ed on a slider surface, causing PFPE degradation. The process is mitigated if the slider surface is coated with a carbon film, or if a nucleophilic ch emical such as X-1P is added to the PFPE lubricant.