RIGID-ROD BENZOBISTHIAZOLE POLYMERS WITH REACTIVE FLUORENE MOIETIES - SYNTHESIS AND CHARACTERIZATION

High purity 2,7‐fluorenedicarboxylic acid chloride was synthesized in a multistep reaction scheme from 2,7‐dibromofluorene. Subsequent polycondensation in polyphosphoric acid of 2,5‐diamino‐1,4‐benzenedithiol dihydrochloride with terephthaloyl chloride and 2,7‐fluorenedicarboxylic acid chloride led to rigid‐rod benzobisthiazole polymers with reactive fluorene moieties. The proportion of fluorene in the resultant polymers was controlled through reaction stoichiometry. Soluble polymers with intrinsic viscosities as high as 33.7 dL/g (methanesulfonic acid, 30°C) were obtained if the polymerization temperature was not allowed to exceed 165°C. Insoluble, presumably crosslinked polymers were obtained at higher temperature (190–200°C). Thermal characterization of the polymers by differential thermal analysis and thermal gravimetric analysis/mass spectroscopy did not disclose any thermal transition to 450°C. Onset of weight loss in air did not occur until over 550°C. Copyright © 1990 John Wiley & Sons, Inc.