Abstract
The aim of this experimental work is to present the reorientationnal dynamics and the orientationnal pinning of a nematic liquid crystal on a solid surface.<br />The first experimental part concerns the study of the reorientationnal dynamics of the 5CB liquid crystal, in its nematic phase, on SiO layers. The observation, under a polarizing optical microscope, of 5CB defect walls motion highlights a solid friction. This friction is opposed to the liquid crystal reorientation on the anchoring layers.<br />In the second part, the precise study of the 5CB/SiO interface shows the existence of an orientationnal quenched disorder. This disorder is characterized by an original angular mapping method. Eventually, the role of the disorder on the dynamics is discussed to explain the nature of the friction torque.