**9. Summary**

two LC domains/layers, as shown in SEM image (**Figure 49(b)**). As LC droplets are

*Sliced polymer morphology: (a) schematic and (b) SEM image of HPDLC film [164, 170].*

In this type of morphology, transmission gratings are prepared from thiol-enebased monomers, under slow curing process and above nematic-isotropic temperature *T*NI of LC (**Figure 50**). In this type of grating, polymer slices are well separated from aligned nematic slices. From the SEM image (**Figure 50(b)**), it is clear that as the concentration of LC is low than the polymer, thickness of the LC slices is also small as compared to polymer slices. The high phase separation degree produces smooth polymer layers and aligned LC layers, which in turn minimizes scattering

Similar to the PDLC films, HPDLC films are based on the scattering and transmittance effect of light from polymer-LC composite film. High monomer concentration and formation of interference pattern during photopolymerization give rise to alternate polymer-rich and LC-rich regions. Depending upon writing set-ups, two types of HPDLC gratings can be formed. Variation in materials and curing conditions can produce different types of morphology in HPDLC composite films. Simple configuration, easy fabrication process and their integration with other

Polymer-LC composite film-based devices are switchable and tunable. The RI of LC droplets embedded in polymer matrix can be tuned using external fields; therefore they can be used for a wide range of display and non-display applications. The low monomer concentration polymer-LC composite film termed as PSLC films can be used for bi-stable reflective displays and haze-free normal- and reverse-mode

The PDLC composite films with the intermediate monomer concentration are distinguished because of their flexibility as well as mechanical strength. The comprehensive list of applications of PDLC film includes haze-free light shutter devices; switchable windows; high-definition Fuoss-Kirkwood spatial light modulators; flat-panel and large area flexible displays; light valves; color projectors; thermal,

optical and strain sensors; electrically tunable focusing lenses; etc. [171].

optical devices make them suitable for practical applications.

light shutters with quick response [68, 110].

absent, scattering losses are low [164, 169].

*Liquid Crystals and Display Technology*

*7.5.3 Sliced polymer morphology (policryps)*

**7.6 Conclusions of HPDLC study**

losses [164, 170].

**Figure 50.**

**8. Applications**

**66**

This chapter encompasses a wide range of LC-related subject matter. It begins with the basics of LC materials, such as definition, history, types, phases and properties of LCs. Information about properties of LC materials offer deep insight in choosing LC material for particular application and also benefit in innovating new applications. Initially applications of LC materials are limited to display world only; now it is finding scope in a non-display world too. A brief outline about applications of LC devices has been followed by an extensive study of polymer-LC composites. The three types of composite films reported in this chapter are as follows:

1.Low monomer concentration composite: PSLC film

2.Moderate monomer concentration composite: PDLC film

3.High monomer concentration composite: HPDLC film

The detailed study of each of the above composite films is about the following:

1.Fabrication technique using the most suited phase separation process.


Precisely, this chapter gives a deep and comprehensive knowledge about LC and some of their applications.

*Liquid Crystals and Display Technology*

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