Flameproofed polyesters prepared by direct polycondensation of aromatic dicarboxylic acids and brominated bisphenols with tosyl chloride and N,N′‐dimethylformamide in pyridine

Brominated aromatic polyesters were successfully prepared by reacting isophthalic acid and terephthalic acid with p‐toluenesulfonyl chloride in pyridine in the presence of N,N′‐dimethylformamide, followed by treating with a pyridine solution of tetrabromobisphenols. The tetrabromobisphenols were synthesized by a facile bromination of their corresponding bisphenols in aqueous acetic acid solution under mild conditions. The polycondensation was significantly affected by the reactivity of bisphenols and the solubility of the resulting polymers in the reaction media. Tetrabromobisphenols with positive linking groups between the aromatic rings and better solubility of the resulting polymers give a more favorable result. The products were nonflammable having limiting oxygen index 59–62 (ASTM D2863‐77) without much sacrifice in thermal stability.