Poly{4,4’-(1-methylethylidene)bisphenylene 3-[4-(4-nitrophenylazo)phenyl]-3-aza-pentanedioate} (pMNAP) was synthesized through the condensation polymerization of 4,4’-isopropylidene-bis-phenol and N-[4-(4-nitrophenylazo)phenyl]imido diacetyl chloride. The polymer solution in tetrahydrofuran (THF) was spin-coated onto a glass substrate to form a film and the process of reversibly photoinduced birefringence was tested. The birefringence induced in the film was observed to a level of 0.04. The biexponential fitting of the birefringence growth and relaxation curves shows two kinds of processes. A fairly low birefringence relaxation occurs after the light is turned off, about 12% at room temperature and less than 50% at 138 degrees C, close to the glass transition temperature (152 degrees C). pMNAP decomposes at about 160 degrees C which prevents its use as a material for optical storage.