A novel series of polybenzazoles with rigid-rod benzobisoxazole cycles and methylene soft segments were designed and synthesized via solution condensation polymerizations from 2

4-diamino-1

5-benzenediol dihydrochloride

terephthalic acid and aliphatic dicarboxylic acids.The molecular structures of polymers were characterized by FT-IR

1H-NMR

WAXD and so on.The polymers are yellowish amorphous powders or solids and own excellent thermal stabilities (Td470℃).All the polymers are soluble in strong protonic acid at room temperature

and the intrinsic viscosities ［］ are in a range of 0.8～0.9 dL/g.A spot of unclosed ring structure fragments in the polymer chain is found via FT-IR and 1H-NMR

and this is due to the obstacle effect of -H of the aliphatic dicarboxylic acid in the polymerization process.The photophysical properties of polymers in methanesulfonic acid (MSA) were investigated by UV-Vis absorption and photoluminescence spectra.The UVVis absorption spectra of polymers in MSA (4.410-4 g/dL) showed blueshift from 429 nm for PBO to 291 nm for PBOC7. The photoluminescence emission spectrum of PBO reveals two sharp and strong peaks while the spectra of PBOCx all show one featureless broad diffuse peak.The Stokes shifts enlarge from 7 nm for PBO to 145 nm for PBOC3.One possible reason is that the gap between conduction and forbidden bands increases with the introduction of soft non-conjugation methylene segment.Further study is under way.