New aromatic benzazole polymers. I. Benzobisthiazole and benzobisoxazole polymers with main-chain triarylamino units

Abstract

Thermally stable, nonrigid-rod poly(benzobisthiazoles), (R)TPA-PBZT, where R = H, Me, NMe2, and OH, and poly(benzobisoxazoles), (R)TPA-PBO, where R = Me, NMe2 containing electron-rich triarylamine groups with various para-substituents (Rs) on the pendent phenyl ring, were synthesized from either 2,5-diamino-1,4-benzenedithiol dihydrochloride or 2,4-diamino-1,5-benzenediol dihydrochloride and the respective triarylamine-based dinitrile or diacid monomer in polyphosphoric acid. Whereas (R)TPA-PBZT polymers were obtained in moderate molecular weights, analogous (R)TPA-PBO polymers were only prepared in low molecular weights. No lyotropic behaviors, characteristic of the unmodified rigid-rod benzazole polymers, as evidenced by the absence of either stir opalescence or birefringence under crosspolarizers, were observed for these homopolymers at about 10 wt % polymer concentration. Among these polymers, only (Me)TPA-PBZT and (NMe2)TPA-PBZT formed cast films with good mechanical integrity. In their pristine state, their film conductivity values were in the range of 10−10–10−9 S/cm at room temperature. Upon exposure to iodine vapor, their conductivities were increased to the maximal values of 5.0 × 10−5 S/cm ((Me)TPA-PBZT) and 4.1 × 10−4 S/cm ((NMe2)TPA-PBZT). © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1909–1924, 1997