Optical and Photonic Polymers

The essential components of such a systems are (1) A highly flexible polymer chain that responds to the alignment needs of the rigid mesogenic units rather than 

Cyclic trimeric and tetrameric phosphazenes with mesogenic side groups also generate liquid-crystalline systems.245,249 

Some debate is evident about the role of the phosphazene polymer backbone in the generation of third-order NLO activity.255 256 

The introduction of bulky, electron-rich side groups, such as those depicted in structures 3.102-3.105 requires the use of special experimental conditions. If introduced via an aryloxide ion by the macromolecular substitutive route, these side groups impart and suffer considerable steric hindrance. Replacement of every chlorine atom along the phosphazene chain by organic side groups may be difficult. 

Some of the latest work on high refractive index polyphosphazenes makes use of polymers that contain both fluoroalkoxy and di- or tri-chlorophenoxy side groups.261 These amorphous glasses are thermally stable up to 400 °C, show a large variation of refractive index with temperature, and refractive index values that vary from 1.39-1.56 depending on composition. Thus, they are candidates for uses in thermo-optical switching devices. 

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P. N. Prasad, Polymeric Materials for Non-linear Optics and Photonics. Polymer 1991,32,1746-1751. 

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