A study of benzobisoxazole and benzobisthiazole compounds and polymers under hydrolytic conditions

✍ Scribed by Ying-Hung So; Steven J. Martin; Karen Owen; Patrick B. Smith; Cheryl L. Karas

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 159 KB
• Volume: 37
• Category: Article
• ISSN: 0887-624X
• DOI: 10.1002/(sici)1099-0518(19990715)37:14<2637::aid-pola38>3.0.co;2-5

✦ Synopsis

The stability of benzobisoxazole and benzobisthiazole compounds and polymers under hydrolytic conditions was studied. 2,6-Bis(4-tert-butylphenyl)benzo [1,2-d; 4,5-dЈ]bisoxazole (1) dissolved in acetonitrile containing sulfuric acid and water at 80°C is stable. A suspension of 2,6-bis[4-(2-benzoxazoyl)phenyl]benzo [1,2-d;5,4-dЈ]bisoxazole (2) in 0.2 N H 2 SO 4 or 0.2 N NaOH solution at 100°C for 21 days is stable. The intrinsic viscosity of a poly(p-phenylene)benzobisoxazole (PBO) fiber sample soaked in 0.2 N H 2 SO 4 , water with 1 wt % polyphosphoric acid (PPA), or 0.2 N NaOH remained the same. Under very severe hydrolytic conditions such as dissolution of compound 2 or PBO in PPA or methanesulfonic acid with residual water followed by coagulation in water, benzobisoxazole underwent bond cleavage to generate carboxylic acid and oaminophenol functional groups. This is in contrast to an earlier hypothesis that the decrease in intrinsic viscosity under these conditions was due to chain association. Poly(p-phenylene)benzobisthiazole (PBT) also underwent bond cleavage under these very severe conditions, which are unlikely to be encountered in normal applications.