Droplet Configuration

The configuration of the liquid crystal droplets in a polymer matrix is the focus of much current research. Many different configurations have been observed and they depend on factors such as droplet size and shape, surface anchoring, and applied fields. This section will describe some of the most common configurations.

The radial configuration occurs when the liquid crystal molecules are anchored with their long axes perpendicular to the droplet walls. This arrangement is shown in the diagram below. Note the point defect in the center of the droplet. The axial configuration of the liquid crystal droplets also occurs when the molecules are oriented perpendicular to the droplet wall, but only when there is weak surface anchoring. This configuration creates a line defect that runs around the equator of the spherical droplet, as seen in the diagram below. When an electric field is applied to a radial droplet, the molecules adopt the axial configuration. The radial configuration is returned when the field is removed. The bipolar configuration is obtained by tangential anchoring of the liquid crystal molecules. This creates two point defects at the poles of the droplet and is shown in the diagram below.

Radial Bipolar Axial

In a typical PDLC sample, there are many droplets with different configurations and orientations. When an electric field is applied, however, the molecules within the droplets align along the field and have corresponding optical properties. In the following diagram, the director orientation is represented by the black lines on the droplet.

 

No Electric Field

Electric Field Applied


Preparation of PDLCs Virtual Textbook Applications of PDLCs