Conformational parameters of the fluorinated poly(p-phenylene-1,3,4-oxadiazole-imide-amide) molecules in dilute solutions in N,N'-dimethylacetamide, NV-dimethylformamide and 96% sulphuric acid were evaluated by using the data of hydrodynamic and dynamo-optical investigations. Optical anisotropy of the statistical Kuhn segment was found to be about half of that for poly(amide-benzimidazole) and close to that previously obtained for poly(p-phenylene-1,3,4-oxadiazole) molecules. The observed effect is referred to the higher equilibrium flexibility of the polymer chain attributed to the hexafluoroisopropylidene units incorporated into the molecule backbone. Noticeable degradation of the polymer molecules in solution in 96% H2SO4 at ambient temperature was detected and characterised. (C) 2003 Elsevier Science Ltd. All rights reserved.