The PS/PMMA blend films were prepared by volatizing the solvent very slowly from the PS/PMMA/THF solution．Various substrates were employed such as glass

PET film

PTFE film and PP film．The SEM pictures showed that the morphologies of both the surface-side (contact with air) and the bottom-side (contact with the substrate) of the film strongly depend on the substrates used．If the substrate was glass or PET films

there were a small amount of PS particles on the bottom-side of the films．On the other hand

a lot of large PS particles could be observed on the bottom-side of the films when PTEF films or PP films were used as substrates．ATR-FTIR analysis was used to detect the composition at the surface side and the bottom side of the blend films．Substrate-segregation was found．It was supposed that this effect might be resulted from the different affinity of PS to the various substrates.