ICR-Spektrometrische Untersuchungen zur Ionenchemie von Flüssigkristallen

Abstract

The voltage holding ratio (VHR) ' the ratio of the control voltage at a pixel at the end and at the beginning of a defined period ' is a very critical parameter for the reliability of liquid crystal displays (LCD). A low VHR causes loss of contrast and image flickering. LC with a high ion affinity can dissolve ions from peripheral display materials (adhesives, polyimide layers, etc.). This reduces the specific resistivity of the LC layer and thus the VHR.Because of this effect, the main focus of this thesis is the determination of proton affinities of 19 liquid crystal model compounds by FT-ICR mass spectrometry. This thesis results in the first available proton affinity ladder of liquid crystal compounds. For the determination of proton affinities by the equilibrium method the knowledge of ion chemistry is necessary to understand the influence of parallel and consecutive reactions (e.g. cluster formation or dissociation reactions) on the proton transfer equilibrium. To examine this influence, computer assisted simulations of gas phase ion/molecule reaction kinetics are presented. Additional, the proton affinities, structures of the protonated molecules and the sites of protonation were calculated by DFT methods. To evaporate the low volatile liquid crystals, a novel inlet system for solid samples was constructed, that allows FT-ICR spectrometric investigations at the baseline pressure of the vacuum system. This system is also presented.