*2.1.5 Discotic phase*

Apart from the rod-like molecules, more advanced-shaped LCs are possible such as disk-like (**Figure 6(a)**) which can give rise to other types of ordering. They were first discovered in carbon precursor compounds with a transient existence by Brooks and Taylor in stable low molecular weight systems [29, 30].

Disk-shaped LC molecules can orient themselves in a layer-like manner termed as the discotic nematic phase. This phase is called as a discotic columnar, if their disks pack into stacks/columns. Again, these columns may organize themselves into rectangular or hexagonal arrays [31]. Discotic LCs are composed of an aromatic core surrounded by flexible chains as shown in **Figure 6(b)**. The aromatic cores allow charge transfers in the stacking direction through the π conjugate system, due to which these LCs become electrically semiconducting along the stacking direction.

**Figure 6.** *(a) Molecular arrangement and (b) example of disk-shaped LC.*

#### *2.1.6 Banana-shaped LC*

Sterically induced packing of bent core (banana-shaped) LC molecules (**Figure 7(a)**) is interesting from many viewpoints. These are the first ferroelectric and antiferroelectric LCs, which contain no chiral carbon atoms; however they can introduce chirality to the system [32]. One example of banana-shaped LC is shown in **Figure 7(b)**.

**Figure 7.** *(a) Molecular arrangement and (b) example of banana-shaped LC.*

*An Overview of Polymer-Dispersed Liquid Crystal Composite Films and Their Applications DOI: http://dx.doi.org/10.5772/intechopen.91889*
