Abstract
A coarse-grained simulation model for a third generation liquid crystalline dendrimer (LCDr) is presented. It allows, for the rst time, for a successful molecular simulation study of a relation between the shape of a polyphilic macromolecular mesogen and the symmetry of a macroscopic phase. The model dendrimer consists of a soft central sphere and 32 grafted chains each terminated by a mesogen group. The mesogenic pair interactions are modelled by the recently proposed soft core spherocylinder model of Lintuvuori and Wilson [J. Chem. Phys, 128, 044906, (2008)]. Coarse-grained (CG) molecular dynamics (MD) simulations are performed on a melt of 100 molecules in the anisotropic-isobaric ensemble. The model LCDr shows conformational bistability, with both rod-like and disc-like conformations stable at lower temperatures. Each conformation can be induced by an external aligning eld of appropriate symmetry that acts on the mesogens (uniaxial for rod-like and planar for disc-like), leading to formation of a monodomain smectic A (SmA) or a columnar (Col) phase, respectively. Both phases are stable for approximately the same temperature range and both exhibit a sharp transition to an isotropic cubic-like phase upon heating. We observe a very strong coupling between the conformation of the LCDr and the symmetry of a bulk phase, as suggested previously by theory. The study reveals rich potential in terms of the application of this form of CG modelling to the study of molecular self-assembly of liquid crystalline macromolecules.
Highlights
Polyphilic liquid crystal (LC) molecules are mesogenic molecules composed of segments with different types of interaction
To study self-assembly of the liquid crystalline dendrimer (LCDr) in the bulk we used a coarse-grained molecular dynamics (CGMD) approach, in which relevant groups of atoms are represented as single particles
As it may be expected from the observations above, with no external field applied, conformational bistability of the LCDr is a serious obstacle towards the formation of a single monodomain phase
Summary
Polyphilic liquid crystal (LC) molecules are mesogenic molecules composed of segments with different types of interaction. Quite recently, successful attempts to study the phase behaviour of bolaamphiphiles were accomplished using both molecular dynamics [22, 23] and dissipative particle dynamics approaches [24, 25] Both methodologies used spherical sites and represented rigid parts of a mesogen structure by a combination of spherical sites. E., should not be able to pass through each other [39] With this proviso anisotropic soft core potentials provide the possibility for studying complex liquid crystal molecules composed of segments with different types of interaction. We use anisotropic soft core particles to study the phase behaviour of a polyphilic macromolecule consisting of a model liquid crystalline dendrimer (LCDr) functionalised by terminal mesogenic groups.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
