Characterization of the dynamics of two- and three-dimensional arrays of dipolar molecular rotors by dielectric spectroscopy

A molecular rotor is a compound with a covalently attached group that may rotate relative to a stationary portion of the molecule. Incorporating a permanent electric dipole moment in the rotating group allows the rotor to be addressed by applied electric fields and provides a mechanism for rotor-rotor interactions. In this thesis, two types of arrays of synthesized dipolar molecular rotors have been studied through dielectric spectroscopy: three-dimensional crystals and two-dimensional surface mounted arrays.;In the three-dimensional arrays, the stationary atoms of the molecular rotor comprise a rigid crystal lattice. Within each unit cell, a fluorinated benzene, providing a dipole moment, may rotate about a fixed axle. I will report characterization by dielectric spectroscopy of the dynamics for crystals that are subject to an asymmetric two-well potential in which the asymmetry is caused by steric interactions between the dipole and its surrounding crystal cage. In an effort to isolate the effects of rotor-rotor interactions, I will also describe results on a system with a larger dipole moment and a sterically symmetric rotational potential where dipolar interactions between rotors are measured. Finally, measurements describing an array of dipolar rotors whose rotation axles are covalently attached normal to a bulk surface will be presented.