Influence of the liquid crystal behaviour on the Langmuir and Langmuir-Blodgett film supramolecular architecture of an ionic liquid crystal

A new luminescent ionic liquid crystal, called Ipz-2, has been synthesised and its mesophase behaviour and also at the air-liquid interface has been studied and compared with Ipz, another ionic pyrazole derivative, with a similar molecular structure, previously studied. The X-ray diffraction pattern shows that Ipz-2 exhibits hexagonal columnar mesomorphism, while Ipz adopts lamellar mesophases. Langmuir films of both compounds are flat and homogeneous at large areas per molecule, but create different supramolecular structures under further compression. Ipz-2 Langmuir films have been transferred onto solid substrates, and Atomic Force Microscopy (AFM) images of the Langmuir-Blodgett films have shown that large columnar structures hundreds of nm in diameter are formed on top of the initial monolayer, in contrast with well-defined trilayer LB films obtained for Ipz. Our results show that Ipz-2 has a tendency to stack in columnar arrangements both in liquid crystalline bulk and in Langmuir and Langmuir-Blodgett films. © 2012 Elsevier Inc.We are grateful for the Spanish and European financial assistance (MEC and FEDER) in the framework of the Projects CTQ2009-13024 and MAT2009-14636-CO3-01. We are also indebted to the Government of Aragón for financial support. I. Giner and V. Perez gratefully acknowledge their predoctoral fellowship from the Government of Aragón and MEC, respectively.Peer Reviewe