PERFLUOROPOLYETHERS WITH ACID END-GROUPS - AN ESR STUDY OF DECARBOXYLATION

An ESR study was performed on photodecarboxylation of perfluoropolyeth er acids, perfluoropoly(alkene oxide) terminated with carboxylic acid end groups. Three commercially available perfluoropolyethers (Fomblin Z, Krytox, and Demnum) with carboxylic ends were examined. ESR spectra of radicals expected from decarboxylation (e.g., R-O-CF2-CF2.) were r eadily observed from each sample exposed to 254 nm radiation at 77 K. The observed, ostensible patterns are shown to be intricate manifestat ions of large anisotropy of alpha- and beta-fluorine hyperfine couplin g tensors and the differing orientations of their principal axes. The principal hyperfine coupling tensors of the relevant F nuclei were det ermined by an iterative simulation process. The structures and conform ations of the radicals thus revealed are in good accord with those giv en by molecular orbital calculations (MNDO). A possible significance o f the decarboxylation process in actual material application is discus sed.