Techniques measuring Maxwell displacement current (MDC) and LB films surface measuring technique have been applied to the study of monolayers of polyamic acid containing azobenzene. MDCs was generated from monolayers on the water surface by monolayer compression and expansion. It was generated when the area per molecule was about $103{AA}^2;and;78{AA}^2$ just before the initial rise of the surface pressure during the 1st and 2nd mixed monolayer compressions cycle, respectively. It was the maximum of MDCs appeared at the molecular area just before the initial rise of surface pressure in compression cycles, and we have found that the increase of aggregations causes the noticeable increase of the surface roughness.