Diffusion and Flow Birefringence of Poly(naphthoyleneimide benzimidazole) in Concentrated Sulfuric Acid

• Published in: Macromolecules 1998-12, Vol.31 (25), p.8831-8839
• Main Authors: Lavrenko, P. N, Pogodina, N. V
• Format: Article
• Language: English
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma980118o

The effect of changes in chemical structure on the equilibrium and kinetic behavior is examined for fully cyclic poly(naphthoyleneimide benzimidazole) (PNI) molecules in dilute solution in 96% sulfuric acid. With this aim, hydrodynamic and dynamo-optical properties were analyzed over a wide range of molecular weight from 6.7 × 10 3 to 2.5 × 10. The M dependence of the translational diffusion coefficient, D, the shear optical coefficient, Δn/Δτ, the intrinsic orientation of the macromolecules in the flow, [χ/g], and the intrinsic viscosity, [η], were established as well as the macromolecule conformation. Results thus obtained indicate the rigid-chain behavior of the PNI molecules. From their comparison with similar data obtained earlier for poly(amide benzimidazole) the conclusion was made that the exclusion of physical mechanisms of the chain flexibility due to the amide group leads to a significantly higher equilibrium rigidity of the macromolecule. At the same time, the comparison of the flow birefringence relaxation time with the viscometric data indicates the intramolecular motions that include a large-scale deformation of the PNI chain increasing with the molecular weight.