Synthesis and Photodegradation of Positive Working Polyimides Derived from 2-Nitro-p-xylyleneoxyamine

Two kind of diamines, 2-nitro- p -xylyleneoxyamine ( 5a ) and p -xylyleneoxyamine ( 5b ) were synthesized and used as monomers together with various tetracarboxylic dianhydrides to prepare the main-chain photodegradative polyimides which exhibited a positive working image upon light irradiation. The photosensitivities of the polyimides and the viscosities of their precursors on irradiation indicated that the nitro group substituted at the ortho position of the benzene ring of the diamine moiety improved the photolytic decomposability of polymers by at least 1−2 orders of magnitude compared with the hydrogen at the same position. Furthermore, much higher sensitivity was attained by using polyimide films such as 6FDA− 5a (polycondensate of 2,2-bis(3,4-dicarboxypheny)hexafluoropropane dianhydride and 5a ) and BHTCA− 5a (polycondensate of bicyclo[2.2.1]heptane-2- exo,3- exo,5- exo,6- exo -tetracarboxylic 2,3:5,6-dianhydride and 5a ), which contained either a bulky trifluoromethyl (−CF 3 ) substituent or a polyalicyclic structure along the polymer backbone. The higher photosensitivities of 6FDA− 5a and BHTCA− 5a (95 and 85 mJ/cm 2, respectively) might be explained by the greater solubilities of the segments decomposed from these polyimides in development solvent. Therefore, a discussion on the photochemical behavior of polyimides studied was presented.