Surface characterization of P3OT thin films by variable temperature scanning force microscopy

In this work variable temperature scanning force microscopy techniques have been used to study poly(3-octylthiophene) (P3OT) thin film samples. Topography images in combination with scanning force spectroscopy have been applied to characterize the morphology and mechanical properties of the P3OT surface. It has been found that at room temperature lamellar islands appears on top of the polymer surface, while at temperatures higher than 35–45 °C these lamellas disappear and the polymer surface becomes homogeneous. This process is reversible and the lamellar structures are recovered when the sample is cooled down. In parallel, local force spectroscopy performed at each temperature shows a marked variation of the mechanical properties at about 30–40 °C, both in the polymer surface as well as in the lamellar islands. This points towards a conformational change in the P3OT molecules which loose planarity disrupting the close packing of the molecules on the lamellas.