Evaluation of surface mechanical properties of organic ultrathin films using scanning force microscope

Surface mechanical properties of polystyrene (PS) film prepared from single droplet of PS solution by ink-jet (IJ) method, and [PS / Polybutadiene (BDA)] (60/40, w/w) blend film were investigated by scanning force microscope. The scanning viscoelesticity microscopic measurements at various temperatures clarified that the relative difference of contrast of the PS and the PBD phase surface becomes small with an increase of temperature. This is due to the relative difference of elasticity of PS and PBD phases. Based on the temperature dependent lateral force measurements, the surface of the PS film prepared by IJ method was in a glass-rubber transition state even at 343 K, in spite of that the bulk Tg was far above 343 K [Tg _(bulk)=378 K]. Similar temperature dependence of lateral force was also observed on the PS film prepared by spin-coating method.