Stability of solutions of aromatic polyamides containing carborane units in the main chain

The stability of aromatic polyamide chains containing 1,7-dicarba-closo-dodecaborane units was investigated in dilute solution by viscometry and sedimentation analysis at 25°C. Traces of impurities in dimethylformamide bring about degradation of the polymer and formation of polyanions, which become manifest in the viscosity by the polyelectrolyte effect. Neutral salts suppress this effect. Degradation is not hindered in an inert atmosphere. The solutions in N,N-dimethylacetamide and N-methyl-2-pyrrolidone are also unstable. No degradation occurs in solutions in tetrahydrofuran stabilized with 2,6-di-tert-butyl-4-methylphenol. Hence, reliable measurements of the molecular characteristics of this polymer can be carried out only in stabilized peroxide-free tetrahydrofuran.