Photoinduced properties of "T-type" polyimides with azobenzene or azopyridine moieties.

• "T-type" azopolyimides with azopyridine or azobenzene moieties were characterized. • Polyimides with azo groups exhibited large modulations of SRGs up to 330 nm. • Cis-trans isomerization was more stable for polyimides with azobenzene groups. • Azopolyimide exhibited good orienting properties of liquid crystal mixture. In this work series of "T-type" polyimides with azobenzene or azopyridine moieties were investigated. It is the first report where the "T-type" polyimides with derivatives of azopyridine were investigated. The cis - trans isomerization in the dark in the solid-state was showed. Polyimides with azobenzene derivatives exhibited higher stability of cis - trans recovery than their azobenzene analogues. For the inscription of the surface relief gratings, two different intensities of light (10 and 45 mJ/cm2) and a number of pulses (10 and 100) were used. Polyimides showed the modulation of SRGs up to almost 330 nm. Our studies showed, that azopolyimides are able to orient the nematic liquid crystal molecules in cell-based on effect at the twisted nematic. The obtained maximum value of t ON was 0.9 ms (1 kHz, 1. 5 V/μm) for polyimide with azobenzene moieties. Azopolyimides may be successfully used in many photonic devices based on the alignment of the liquid crystal mixture i.e. LC diffraction gratings, Fresnel lens, Vortex, in a photo-pattering technology for creating radical and azimuthal orienting layers. [ABSTRACT FROM AUTHOR]