*7.5.3 Sliced polymer morphology (policryps)*

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 losses [164, 170].

### **7.6 Conclusions of HPDLC study**

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 optical devices make them suitable for practical applications.

### **8. Applications**

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 light shutters with quick response [68, 110].

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].

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

When the monomer concentration is higher than the LC concentration, HPDLC films get formed. HPDLC films are known to be a promising technology because they can be used in 3D display, fiber optics, data storage, zoom lenses, image capture systems, beam vibration sensor, etc. [172].

It can be concluded that the LC's inherent optical and dielectric anisotropy can be effectively used in a display as well as non-display devices.
