A MOLECULAR SIMULATION STUDY OF A CYCLIC SILOXANE WITH ATTACHED BIPHENYLYL 4-ALLYLOXYBENZOATE MESOGENS

A molecular simulation study of a cyclic siloxane macromolecule based on a pentamethylcyclosiloxane core and biphenylyl 4-allyloxybenzoate m esogenic units is reported. Molecular dynamics and semi-empirical calc ulations were used to provide insight into the conformation and the di electric properties of the material. Out of three proposed conformatio ns of the molecules, a cylindrical conformation was found to be the mo st probable. The intermolecular interactions were found to be optimize d for the case where the mesogenic groups were planar and parallel to each other. The calculated mesogen length and inter-mesogen distances were consistent with available X-ray data. Electrostatic interactions were found to make a very significant contribution to the total energy . For the cylindrical model, the major component of the dipole was cal culated to be along the long axis of the molecules. This is consistent with the alignment of the molecules parallel to a low frequency appli ed electric field as found experimentally.