Various substituted chitosan (PHCS) were prepared at 125℃ from chitosan and phthaloyl anhydride by controlling both the reaction time and molar ratio．The synthesis reaction mechanism and chemical structure of products were characterized by FTIR．Different compositions of amic acid-chitosan and imide-chitosan were found in these products．the former was converted into the latter at 125℃ after reacting relatively long time．The existence of amic acid-chitosan was proved by the good solubility and broad C—H stretch bands．as well as characteristic double bands of their salt (1455 and 1558 cm-1)．The existence of imide-chitosan was proved by characteristic double bands at 1712 and 1775 cm-1．The total degree of substitution(DSTotal) was determined with 1H-NMR．The degree 0f substitution for both amic acid (DS1) and imide(DS2) was measured by element analysis．The polarized optical microscopy was employed to study the texture and the critical concentration(c*) of liquid crystal phase in dichoroacetic acid．The c* (in polymer weight fraction) at which liquid crystalline ordering was found to be present was 0.12～0.18 for some PHCS

and too high (over the solubility of polymer)to be detected for PHCS with high relative degree of amic acid substitution．The c* was found to be affected mainly by the degree of substitution of amic acid．The c* increased directly with the increase of DS1．The influence of DS1 was significantly larger than that of DS2 on the critical liquid crystalline behavior of PHCS．