The surface properties of hydroxypropylcellulose (HPC) and polyethylenimine (PEI) blend films prepared by solution casting method before and after annealing were investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and contact angle measurements. SEM and AFM analysis of the blends revealed that the PEI component segregated on the surface of the air-surface side of the blend films with increasing annealing temperature. The band intensity of PEI component at 1630 cm(-1) also increased depending on annealing temperature. The water contact angle decreased abruptly with increasing annealing temperature and reached almost 31 degrees on the surface of the air-surface side of the blends at 150 degrees C. The results of these studies showed that the PEI chains with low surface energy segregated or enriched mainly on the surface of the air-surface side, and that, on the other hand, HPC chains with high surface energy oriented to the surface of the glass-surface side and inside of the films with increasing annealing temperature. (C) 2009 Elsevier B. V. All rights reserved.