The degradation mechanism of perfluoropolyethers (PFPE) under UV exposure was investigated. Chain scission was found to be in the methylene (fluorine) and the hydroxyl end chain rather than in the methylene oxide and methylene oxide main chain where the catalytic Lewis acid degradation was started. This suggests that UV light creates low energy electrons, which initiate the formation of radicals resulting in the chain scission of PFPE. Chain scission was accelerated under an air environment by the oxidation through radical propagation in the methylene (fluorine) end. In addition, the effect of UV degradation on the physical properties of Z-DOL was determined. UV exposure caused the dramatic weight loss of Z-DOL even at low temperatures that were far below the evaporation temperature of Z-DOL. On the other hand, the thermal stability of UV degraded Z-DOL was enhanced by increasing the molecular weight due to the chain extension through reactions between the formed radicals.