Dynamics of Molecular and Collective Modes in Filled Nematic

Abstract

The influence of filling of 5CB with hydrophilic and hydrophobic Aerosil particles on dynamics of molecular and collective modes has been investigated by broadband dielectric spectroscopy (BDS) and photon correlation spectroscopy (PCS). BDS provides information on reorientational motion of polar molecules while PCS probes dynamics of collective modes associated with director fluctuations. Two bulklike dielectric modes due to the rotation of molecules around short axes and the librational motion were observed in filled 5CB. We found that the properties of 5CB are considerably affected by the filling. A low frequency relaxation process and dispersion of dielectric permittivity due to conductivity were observed. The treatment of the surface of filling particles has strongest influence on the properties of the slow process and it is less important for molecular modes. PCS experiment shows that two new relaxation processes appear in filled 5CB in addition to the director fluctuations process in bulk.

Key Words:

• filled nematic
• dynamical behavior
• relaxation