Fechan A. Physical processes during the cholesteric-nematic transition in strong polar induced cholesterics.

At the thesis modern theoretical models of supermolecular spiral structure creation process and cholesteric-nematic transition effect in induced cholesterics are considered. It is shown, that there is no satisfactory cholesteric phase model at present time, which could give a possibility to carry out the quantitative calculation of supermolecular structure parameters for multicomponent systems. The physical properties of strong polar induced cholesterics and cholesteric-nematic transition (CNT) electrooptical parameters are studied in a wide temperature range. The cholesteric-nematic tansition features in thing liquid crystal layers are studied. The correlations between induced cholesterics physical properties, real cells constructive parameters and colesteric-nematic transition electrooptical characteristics are fixed. It is found, that the strong polar component (boroxane) concentration increasing leads to both forward and inverse CNT critical voltages growth. The dynamics of forward transition criti cal voltage growth by far exceeds the inverse transition critical voltage growth, that leads to increasing of field hysteresis loop value. Such critical fields behaviour is coused by spiral structure pitch decreasing at chiral dopant constant concentration, from the one hand, and by the mixture elasticity constants growth - from the other hand. Moreover, field hysteresis relative loop value growth is coused in general by elasticity constants increasing. The method of induced cholesterics elastic properties defining is elaborated. The regularities of focal-conic texture creation in liquid crystal layer during the CNT are fixed. It is shown, that the supermolecular spiral structure pitch critical value, when CNT effect occurs without focal-conic texture creation, is defined by the twist elastic constant and surface energy densities of the corresponding director states ratio. The results of this work can be used for new devices of reflection and processing of information designing and for improvement of existing devices working characteristics.