Thickness anomalies in supported polystyrene films with thicknesses comparable to the radius of gyration

Abstract

We report on X-ray reflectivity of ultrathin polystyrene films with thickness A, which is comparable to the radius of gyration Rg. Tiny jumps in thickness, accompanying an increase in surface roughness and decrease in electron density, are reproductively observed at around 80 °C and 92 °C only with increasing temperature. For films thinner than Rg, the jump at 92 °C disappears. However, films of 2Rg thick, the jump at 80 °C is hardly observed with a faint trace in slope at this temperature. For much thicker films, neither jump appears in heating experiments. The thickness dependent complex behavior observed in non-equilibrium condition is considered to be some indication of surface and confined effects, because the characteristic film thicknesses coincide with the order of Rg. © 2009 The Society of Polymer Science.