Abstract: A series of polybenzoxazoles (co)polymers bearing crankshaft units in the main chain was synthesized by the conventional solution polycondensation of 4, 6-diaminorescinol dihydrochloride, terephthalic acid (TA)and 2,6-naphthalene dicarboxylic acid(NDA).All of the polymers show lyotropic liquid crystal behavior in polyphosphoric acid(PPA) and methanesulfonic acid (MSA).The polybenzoxazoles exhibit an excellent thermal resistance although the crankshaft monomer has been introduced into the polymer backbone.The temperature for the 5% weight loss of all the polymers is above 600 ℃.The X-ray diffraction analysis results show that the series of the polymers has a high crystallinity.The introduction of NDA makes a slight decrease in the thermal resistance of the polymers.The maximum absorption peak in the UV-Vis spectra can be adjusted according to the amount of 2,6-naphthalene units in the polymers, which indicates the potential application of the polymers as optoelectric materials.

Key words: Polybenzoxazoles, Copolymer, Liquid crystal, Thermal resistance