Abstract
A series of three polybenzazoles containing hexafluoroisopropylidene (HFIP-PBZs) were produced in order to study the effect of including the HFIP group into the rigid PBZ backbone. The monomers, 2,5-diamino-1,4-benzenedithiol dihydro-chloride and 4,6-diamino-1,3-benzenediol dihydrochloride, were synthesized and puri-fied. The monomer 1,2,4,5-tetraaminobenzene tetrahydrochloride is commercially avail-able and was purified by recrystallization. These mononmers were polymerized with 2,2-his(4-carboxyphenyl)-I1,,1,3,3,3-hexafluoropropane (6F-diacid) by a polycondensation reaction in polyphosphoric acid employing the P205 adjustment method to give polymers in good yields with inherent viscosities ranging from 0.33 to 1.18 dl/g. These polymers show an increase in solubility over non-HFIlP containing PBZs and display excellent thermal stability by thermogravimetric analysis (540-568°C in argon). Isothermal aging in air of the polymers for 300 h afforded weight losses between 3.27 and 12.0%.
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