Structures and Dynamics of Ultra-thin Smectic Films

Structures and Dynamics of Ultra-thin Smectic Films

Smectic films consisting of only one or few molecular layers are prepared by spin-coating from solution. By controlling the concentration of the smectic material in the spin-coating solution, films with a defined small number of smectic layers can be prepared. Unless the concentration is precisely tuned to certain values, the topmost smectic layer of the films is formed only partially, i.e., it is either fragmented into isolated islands or it shows a porous structure. There is a well-defined relation between the concentration of the liquid crystal in the spin-coating solution and the resulting surface structure, thereby enabling the targeted generation of island or pore structures. These films might be of interest for the preparation of structured two-dimensional soft matter systems.

We are currently conducting single molecule diffusion measurements [B. Schulz, D. Täuber, F. Friedriszik, H. Graaf, J. Schuster, and C. von Borczyskowski, Phys. Chem. Chem. Phys. 12, 11555 (2010)] in the ultra-thin films described above as well as in freely suspended smectic films. For this method, one determines the Brownian motion of single fluorescent probe molecules which are dissolved in the liquid crystal matrix. The following animation gives an example of fluorescent single molecules moving within a 16 × 16 μm2 area of a smectic film:

Find more information:

Surface structure of ultrathin smectic films on silicon substrates: Pores and islands
B. Schulz and Ch. Bahr, Phys. Rev. E 83, 041710 (2011).
DOI: 10.1103/PhysRevE.83.041710

Nanoscale viscoplastic behavior of smectic liquid crystals and its application in nanolithography
B. Schulz, P. Steffen, and Ch. Bahr, J. Appl. Phys. 115, 074302 (2014).
DOI: 10.1063/1.4865796

Single-molecule diffusion in freely suspended smectic films
B. Schulz, M. G. Mazza, and Ch. Bahr, Phys. Rev. E 90 040501(R) (2014).
DOI: 10.1103/PhysRevE.90.040501

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