Conformational and optical properties of polyimide molecules with hexafluoroisopropylidene groups in solution

The translational diffusion and flow birefringence in DMF solutions of new fluoro-containing polyimides based on diamines, trinitrotoluene derivatives, are studied. Based on hydrodynamic and dynamooptical measurements, the molecular parameters and optical anisotropy of macromolecules are calculated and compared with the corresponding characteristics of other PIs. A marked coiling degree of polymer chains for the tested PIs in solution (the Kuhn segment A = 50 ± 10 A) and a low segmental anisotropy (Δα = (110-165) x 10 -25 cm 3 for PIs with different side radicals) are explained in terms of the flexibility structural mechanism by the occurrence of alternating meta-phenylene, imide, and hexafluoroisopropylidene groups in PI chains.