Degradation of fluorinated polyoxadiazole in wet acidic media

- Hydrolysis of fluorinated polyoxadiazole occurs in acidic aqueous conditions.
- Degradation of fluorinated polyoxadiazole also happens in wet acidic media.
- Cross-linking of F-POD takes place using diamine in similar acidic conditions.

The chemical degradation of poly(2,5-(4,4'-(hexafluoropropylidene)diphenyl)-1,3,4-oxadiazole) (F-POD) was studied in wet acidic media using a variety of analytical techniques. It was found that in aqueous acidic solution, F-POD degradation increased with higher acidity (lower pH) and can reach levels of up to 20% in mild acidic conditions (pH 5.5). Furthermore, residual water present in chloroform was found to be capable of inducing degradation in the fluorinated polymer as well. A mechanistic explanation of the hydrolysis is proposed, which implicates the electron withdrawing effect of the hexafluoroisopropylidene group in the oxadiazole ring opening. The initially linear polymer is suggested to be transformed into a bi- or three-dimensional polymer (i.e., a branched or cross-linked structure) due to the attack of 1,3,4-oxadiazole ring by carboxylic hydrazide, causing a considerable loss of its solubility in organic solvents. Finally, we demonstrate that F-POD is susceptible to cross-link via relatively simple chemistry.