Phase diagram of a rigid rod system with attractive end groups

This manuscript reports molecular simulations of bolaamphiphiles, elongated molecules with attractive moieties on each end. An initial portion of the manuscript deals with the algorithms developed to obtain the macroscopic behaviour of these fluids from the knowledge of their interactions at the molecular level.

The models of molecules considered here are coarse-grained representations consisting of a non-flexible elongated core (akin to a pencil) with simple self-attractive sites (heads) on each end. The strength of the attraction between the heads is varied and we report how it affected the different phases the material can exist in. By its elongated nature, the non-attractive rigid molecule will exhibit liquid crystal behaviour, i.e. it will show microscopic order albeit being a fluid.  The different strengths of attraction and temperatures induced either isotropic (simple liquid) behaviour, nematic (an alignment of the elongated cores) or Smectic A ( alignment plus layering in the direction of the alignment) liquid crystal phases.

Authors: Andrew J. Crane, Erich A. Müller