Rheometry, ellipsometry and atomic force microscopy (AFM) have been used to monitor the reaction at a poly(styrene/malcic anhydride) (SMA)/polyamide 6 (PA6) interface at 200 degrees C for various period of time. The interfacial reaction can be divided into three distinct stages by the results of complex viscosity (eta*). In the initial stage, eta* increases with time and there is a second-order reaction to a first-order reaction transition. In the second stage, a reaction depletion layer forms and eta* does not change with the reaction time. In the late stage, eta* increases slowly again. The interfacial thickness increases with time in the early stage then keeps constant by building up the undulated interface. Moreover, there is an asymmetry interface which deeply develops into SMA layer as proved by ellipsometer. (c) 2005 Elsevier Ltd. All rights reserved.