Photorefractive formulations

An organic photorefractive system has to contain different functional groups providing for the generation, transport, and trapping of charge carriers. Moreover, a plasticizing function is required for certain formulations. Apart from the 

Polymer VII belongs to a group of conjugated polymers containing porphyrin or phthalocyanine complexes synthesized by Lu et al. [16]. Here, the polymer backbone consists of phenylene vinylene moieties, which facilitate hole trans- 

Chart 4.2 Low molar mass compounds employed in photorefractive formulations. 

---

Because of the versatility of the polyurethane system it is possible to introduce comonomers which can affect the physical properties of the derived polymers. For example, photo cross-linkable polyurethanes are formulated using 2,5-dimethoxy-2,4 -diisocyanato stilbene as a monomer (76). Comonomers, having an azoaromatic chromophore, are used in optical bleaching applications (77), or in the formation of photorefractive polymers (78). The latter random poljnners have second-order nonlinear optical (NLO) properties. Linear poljnners are also obtained from HDI/PTMG and diacetylenic diols. These polymers can be cross-linked through the acetylenic linkages producing a network polymer with properties similar to poly(diacetylenes) (79). 

---