Fractionation in polydisperse systems of spherocylindrical rods: the influence of attractive interactions and adjacent substrates

Abstract

Systems of spherocylindrical rods with polydisperse length distribution are investigated with the help of Monte Carlo simulations. For a sufficiently high pressure, a demixing of long and short rods is observed. The degree of fractionation increases with the strength of the attractive interaction. In systems of attractive rods, the largest rods arrange themselves in a hexatic monolayer, whereas in hard rod systems, a less-ordered nematic droplet forms with a broader length distribution. Fractionation effects are also investigated for a rod system in contact with a smooth planar substrate. At low pressures, the density of long rods close to the substrate is reduced. For a sufficiently high pressure, the enhanced order close to the substrate leads to an aggregation of long rods in the vicinity of the substrate.

Keywords:

• Fractionation
• Polydisperse systems
• Spherocylindrical rods
• Attractive interactions
• Adjacent substrates

Acknowledgements

We thank Reinhard Lipowsky and Tanja Schilling for fruitful discussions. Support from the Deutsche Forschungsgemeinschaft via Sonderforschungsbereich 448 is gratefully acknowledged.