Coarse-grained simulation studies of a liquid crystal dendrimer: towards computational predictions of nanoscale structure through microphase separation

Coarse-grained simulations are described in which the behaviour of a system of model liquid crystalline dendrimer molecules is Studied in both liquid and smectic-A liquid crystalline phases. The model system is based on a third generation carbosilane dendrimer, which is functionalised at the surface by short polymeric chains terminated in mesogenic units. The design of the coarse-grained model is based on initial Monte Carlo studies of a single carbosilane molecule at an atomistic level, which yield structural data. The coarse-grained dendrimer is represented in terms of a combination of spherical sites representing the dendrimer core and polymer chains, and spherocylinders representing the mesogenic groups. A strong coupling is seen between internal molecular structure and molecular environment, with individual dendrimer molecules undergoing a remarkable transition from spherical to rod-shaped at the isotropic-smectic phase transition. The driving force for mesophase formation is provided by nanoscale microphase separation of mesogens and the dendrimer core.