Aromatic poly(benzoxazole)s from multiring diacids containing (phenylenedioxy)diphenylene or (naphthalenedioxy)diphenylene groups: Synthesis and thermal properties

Poly(arylether benzoxazole)s (PAEBOs) were prepared from a series of fully aromatic dicarboxylic acids containing (phenylenedioxy)diphenylene or (naph thalenedioxy) diphenylene groups and 3,3'-dihydroxy-4,4'-diaminobiphenyl (I ) or 4-4'-(hexafluoroisopropylidene)bis(2-aminophenol) (II) through high-te mperature direct polycondensation. A phosphorous pentoxide/methanesulfonic acid mixture or trimethylsilylpolyphosphate was used as a condensing agent. All the PAEBOs were amorphous and soluble in strong acids, and those deriv ed from II were also readily soluble in polar organic solvents. Flexible fi lms were cast from their chloroform solutions. The PAEBOs showed inherent v iscosity values of 0.68-2.06 dL/g (CH3SO3H, T = 30 degrees C, c = 0.15 g . dL(-1)). Thermal analysis indicated glass-transition temperatures ranging f rom 236 to 270 degrees C and thermal stability (5% weight loss) in nitrogen up to 526 degrees C. (C) 2000 John Wiley & Sons, Inc.