Understanding the interdiffusion and chain orientation of partially miscible polyimide (PI) is essential to achieve a good adhesion performance between two consecutive layers when manufacturing multi-layer PI films. In the present study, bilayer PI films are made from two poly(amic acid) (PAA) solutions that are similar in their molecular structure using two different drying methods, direct multi-layer (DML) and layer-by-layer (LBL). The interdiffusion at the interface between two PAAs occurs during the drying process, and the extent of interdiffusion is affected by both the amount of solvent that acts as a plasticizer and the period of time they make a contact. Raman spectroscopy shows that the interdiffusion width increases with time (t) as similar to t(beta), and the exponent beta increases as the PAA contains more solvent. This explains why the interdiffusion width of the cured PI made by DML is larger than that made by LBL. The variation in chain orientation of each layer is also investigated using the polarized Raman spectroscopy. The chain orientation is related to the interfacial stress between two layers as it affects thermal expansivity of PI. It is observed that the chain orientation of the bottom layer, which consists of relatively rigid chain structure, can be varied more significantly according to the drying condition. In the bilayer PI film made by the LBL method, the degree of in-plane chain orientation of the bottom layer becomes reduced compared to the single-layer PI when the layer is dried at lower temperature, which originates from the fast diffusion of solvent in the top layer into the bottom layer. (C) 2015 Elsevier Ltd. All rights reserved.