Synthesis and characterization of aromatic poly(benzobisthiazole)s and poly[oxy(bisbenzothiazole)]s containing flexible linkages

Aromatic poly(benzothiazole)s (PBT)s were prepared by direct polycondensation of multi-ring dicarboxylic acids containing aryl ether or 2,2?-hexafluoroisopropylidene flexible groups and 2,5-diamino-1,4-benzenedithiol (PBT I) or 3,3?-oxybis(6-aminobenzenethiol) (PBT II) using poly(phosphoric acid) or poly(phosphoric acid)/ methanesulfonic acid as condensing agent and solvent. Inherent viscosities were in the range 0.62-2.68 dL/g, indicating moderate polymerization degrees. The molecular structure was checked by FTIR and H NMR spectroscopy. Good solubility in polar aprotic organic solvents was observed for PBTs derived from monomers containing flexibilizing groups in both moieties. Glass transition temperatures ranged between 268 and 312°C for PBTs I, and between 219 and 233°C for PBTs II. Both PBTs I and II possessed good thermal and thermooxidative stability.