Structural phase transition in ultrathin films of disk-shaped molecules

Abstract

We have used grazing-incidence X-ray diffraction and atomic force microscopy to study Langmuir-Blodgett films of 2-(3-hydroxypropyl)oxy-3,6,7,10,11-pentapentyloxytriphenylene, a disk-shaped molecule which also forms a bulk liquid crystalline columnar phase. Upon heating, we observe a phase transition from a low symmetry ordered crystalline structure to a high temperature liquid crystal. The transition is reversible, with considerable hysteresis.