Ordering and director-field configuration in single droplets of liquid crystals probed by X-ray microdiffraction

¹ Dipartimento di Fisica e Ingegneria dei Materiali e del Territorio and INFM Università di Ancona - Via Brecce Bianche, I-60131 Ancona, Italy
² European Synchrotron Radiation Facility - Boîte Postale 220 F-38043 Grenoble Cedex, France

Received: 7 February 2002
Accepted: 11 April 2002

Abstract

X-ray microdiffraction (μ-XRD) is used for the first time to probe the liquid crystal (LC) ordering in confined LCs. We report on the direct observation of the director field in single droplets of nematic LCs embedded in a solid polymeric matrix (polymer-dispersed LCs). The bipolar configuration is identified in droplets with radius . Both the director distribution function and the droplet order parameter are obtained from diffraction patterns and the results are in excellent agreement with theoretical calculations. This technique is unique in its application to dispersed mesophases in that it allows to probe the local (μm length scale) LC ordering. The possibility of focusing measurements on single droplets eliminates the problems connected with averaging, which are typical of other techniques. Our results prove that μ-XRD is a novel and valuable tool in the study of confined LCs and open new exciting opportunities for future investigations.