Benzofuro[2,3-b]benzofuran-2,9-dicarboxylic acid (I), 4,4'-[sulfonylbis(p-p
henyleneoxy)]dibenzoic acid, and 2,7-biphenylene dicarboxylic acid were rea
cted with a number of diaryl ethers in phosphorous pentoxide/methane sulfon
ic acid (PPMA) media. Diacid I also was reacted with an equimolar mixture o
f two diaryl ethers. FT-IR spectroscopy and elemental analysis data confirm
ed the molecular structure of the polymers. They show good thermal stabilit
y.