Polybenzimidazole (PBI) molecular weight and Mark‐Houwink equation

The molecular weight, and intrinsic viscosity of polybenzimidazole (PBI) and its phosphonylated derivatives are reported. The relationship between intrinsic viscosity η] and weight average molecular weight (M_w) for PBI has been established in H₂SO₄ and DMF‐LiCl. The Mark Houwink constants K_w of 5.2 × 10^?3 mL/g, α of 0.92 for H₂SO₄ solvent systems and, K_w of 3.2 × 10^?2 mL/g, α of 0.754 for DMF‐LiCl solvent system have been determined at M_w < 65,000. The intrinsic viscosity of PBI determined by the Huggins–Kraemer method was compared with a single point method, and found that both methods fit well for PBI in relatively low concentration solvent system, giving ～ 99% accuracy. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009