Provitamin D photochemistry in liquid crystal and soft matter physics: Fundamental and applied aspects

2^nd International Conference and Exhibition on Materials Science & Engineering

October 07-09, 2013 Hampton Inn Tropicana, Las Vegas, NV, USA

Irina Terenetskaka

Accepted Abstracts: J Material Sci

Abstract :

Provitamin D photoisomerization is the first step of biologically important process of vitamin D synthesis under solar UV irradiation. Our first study of the photoreaction in a nematic LC matrix was inspired by the idea of vizual following the photoreaction course in real time, i.e. developing personal UV biodosimeter for estimation of the vitamin-D-synthetic capacity of sunlight in situ. This goal was accomplished by observing the changing number of Cano-Grandjean stripes in the wedge-shaped cell under UV irradiation. Later on, the easiest detection of previtamin D synthesis in situ was carried out by following the LC cell color change as a result of accumulated UV dose. Recently a new method for visual detection of provitamin D photoconversions has been proposed that is based on the determination of an azimuth of a disclination line in the so-called θ-cell. Besides, two methods of spectral monitoring of the vitamin-D-synthetic capacity of sunlight in situ have been developed and patented using soft media (polymer and hydrogel) as matrix material. Unique effect of rotation of provitamin D rod-like microcrystal during its dissolution at the top of nematic droplet was observed, and the dynamics of cholesteric helix induction was interpreted. To the best of our knowledge, this was the first observation of a monodirectional rotation driven by direct transformation of chemical dissolution energy into mechanical rotation energy. Using provitamin D as a photosensitive chiral dopant, the polarization properties and structure changes of plane-oriented nematic LCs were studied, and the chirality transfer effects under UV irradiation were investigated in detail using multi-domain LC cells. Besides, specific features of provitamin D photoisomerization in nematic and cholesteric liquid crystals were revealed, and the increase in the efficiency of cis-trans isomerization as compared to ethanol solution was studied in dependence on the temperature and provitamin D concentration. Altogether, the results obtained indicate the collective character of cis-trans isomerization in ordered liquid crystalline matrices.

Biography :

Irina Terenetskaya has completed her Ph.D. at the age of 29 years from the Institute of Physics, NAS Ukraine and postdoctoral studies on Solid State Physics from Kiev State University. She is Professor in Optics & Laser Physics and works as leading scientist at the Institute of Physics, NAS Ukraine. She has published more than 100 papers in reputed journals and is serving as a reviewer. At Biomedical Optics?94, her outstanding paper was rewarded by Theodore H. Maiman Award from the Laser Centers of America. She has got several international fellowships, was invited in European Universities, participated in several international projects collaborating with DLR, LLNL and NOAA/ARL, and presented her work at several EC and NATO workshops.