Phase behavior of symmetric disk-coil molecules

Abstract

We investigate the self-assembly of symmetric disk-coil molecules using Monte Carlo simulations in the NPT ensemble. Our molecules are composed of a planar disk (head) that is covalently bonded to a single coil (tail), and can be regarded as disk-coil copolymers. For this system, we observe a variety of phases depending on the temperature and the effective interactions between the disk and coil regions. In particular, we find a disordered, a lamellar, a perforated lamellar, and a crystal phase. Furthermore, the orientational correlation (or ordering) of the disks within the crystal phase is found to be stronger compared to the pure disk case, which we also explicitly simulate. The enhanced order is due to the confinement imposed by the mesophase formation. Our results are relevant for organic photoactive (typically planar) molecules that are functionalized with alkyl tails to improve their processing properties as well as their long-range order in the solid phase, and can also help to rationalize some biologically observed phases of chlorophyll seen in the photosynthetic apparatus of green bacteria.