Photoconductive polyimides

Sensitized for blue-green or red light, photoconductive polyimides and liquid crystal mixtures of cyanobiphenyls and azoxybenzene have been used in spatial light modulators [255-261]. Modulation procedure was achieved by means of the electrically controlled birefringence, optical activity, cholesteric-nematic phase transition, dynamic scattering and light scattering in polymer-dispersed liquid crystals. 

Fig. 31. Photosensitivity spectra of the photoconductive polyimide-licjuid crystal modulator for positive right) and negative (left) bias on the photoconductor. Voltages in V 80 (/,/ ) 20 (2,2) [259]...

New types of photoconductive polymers containing imide groups have been described [330-332]. They show high photosensitivity and a set of other valuable properties. Takimoto et al. [331] developed novel photoconductive polyimides, whose monomer units are composed of a series of thiophenylene moieties and... 

Besides polyimides, photoconductive polymers with conjugated bonds also can be successfully used in liquid crystal spatial light modulators [262-264], The high resolution, mechanical and electrical stability and possibility for sensitization of the photosensitivity make the use of organic polymer photoconductors in spatial light modulators very attractive. Devices such as phase... 

The polyimide-base PR system [79,80] was designed on the premise that porphyrin-electron acceptor (quinones or imide moieties) systems are well-known model compounds for photosynthetic processes and exhibit very interesting charge transfer properties [81], A high quantum yield of charge separation can be achieved in these systems. Polyimides are found to be photoconductive and allow charge transport [82], Furthermore, polyimides possess high Tg and therefore, the electric field-induced dipole orientation can be fixed after imidization [83],... 

Polyimides carrying NLO chromophores are synthesized. The materials exhibit high Tg ( 220°C). The photoconductivity of polyimide Vin (Scheme 7) is determined to be 1.1 x 10-12 cm/(f2W) under an external field of 150 V/p,m at X = 690 nm and I = 5.9 mW/cm2. After the sample is corona poled, an optical gain coefficient of 22.2 cm-1 under zero field conditions is detected. Polyimide IX exhibits an optical gain of 15 cm-1, which is very close to the optical loss (17.6 cm-1). 

Rumyantsev, B. M., Berendyaev, V. L, and Kotov, B. V. Photoconduction Kinetics and Nature of Intermediate Photogeneration Centers in Soluble Photoconduetive Polyimides. Photochemistry and Magnetochemistry. J. Phys. Chem., 73(3), 538547 (Russian) (1999). 

Soluble polyimides (50) with enhanced photoconductivity as well as extreme mechanical strength and... 

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