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

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 tON 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

The comparison of electrooptical properties of PDLC liquid-crystalline composites in visual and near-IR ranges

Electrooptical properties of conventional Polymer-Dispersed Liquid Crystals (PDLC) composites were compared in visual and near-IR ranges for the electrically-induced light transmission effect. It was confirmed that the most important for the optical contrast value is the matching of refractive indices of the polymer matrix and dispersed droplets of liquid crystal, as well as matching droplet size and wavelength of incident radiation. The optimization of electrooptical parameters of such materials needs new liquid-crystalline mixtures dedicated for near-IR range. The studied effect can be applied for manufacturing window glasses with electrically adjusted transmission of infrared radiation. Keywords: material science, liquid-crystalline composites, PDLC, electrooptics, infrare

Protein Determination with Molecularly Imprinted Polymer Recognition Combined with Birefringence Liquid Crystal Detection

Liquid crystal-based sensors offer the advantage of high sensitivity at a low cost. However, they often lack selectivity altogether or require costly and unstable biomaterials to impart this selectivity. To incur this selectivity, we herein integrated a molecularly imprinted polymer (MIP) film recognition unit with a liquid crystal (LC) in an optical cell transducer. We tested the resulting chemosensor for protein determination. We examined two different LCs, each with a different optical birefringence. That way, we revealed the influence of that parameter on the sensitivity of the (human serum albumin)-templated (MIP-HSA) LC chemosensor. The response of this chemosensor with the (MIP-HSA)-recognizing film was linear from 2.2 to 15.2 µM HSA, with a limit of detection of 2.2 µM. These values are sufficient to use the devised chemosensor for HSA determination in biological samples. Importantly, the imprinting factor (IF) of this chemosensor was appreciable, reaching IF = 3.7. This IF value indicated the predominant binding of the HSA through specific rather than nonspecific interactions with the MIP