Studies on surface molecular motion of oligomeric polystyrene by differential scanning calorimetry

There are many studies on the surface molecular motion of polymer films 1 ], but no report on surface thermal properties of polymer because of experimental difficulties. The thermal property of oligomeric polystyrene (PS) was investigated by differential scanning calorimetry (DSC) in the present study. In order to increase the ratio of surface area to volume of PS particles, the DSC samples were prepared by mechanically grinding mixtures of PS and Al₂O₃ powders. The grinding mixtures of these powders with low particle size showed a transition at a low temperature of 14–17 °C (much lower than the bulk glass transition temperature, T_g), and this low‐temperature transition was dependent on the size of PS particles. This transition seems to result from the surface molecular motion of the activated surface layer of PS. Copyright © 2000 John Wiley & Sons, Ltd.