Reorientational processes were investigated for liquid crystalline side chain polymers, displaying a nematic phase, by means of dielectric relaxation, electro-optical relaxation and switching studies. The results on the dynamical responses were analyzed in terms of the appropriate theories, i.e., in terms of the Landau de Gennes phenomenological approach (electro-optical relaxation), the continuum approach (switching) and the extended Debye approach (dielectric relaxation).The main results of such an analysis are that the three different models yield dynamical quantities such as the viscosities and the response times, which are consistent with respect to each other. This leads. first of all, to the conclusions that the basic process controlling all three phenomena is the reorientational motion of the mesogenic unit about the short axis and secondly that the rotational process is controlled in the case of side chain polymers by fluctuations rather than by small step rotational diffusion.
A theoretical treatment of the behaviour of liquid crystalline side chain polymers containing photostationary mesogenic units such as azobenzene is given in the presented paper. The phenomenological theory gives both the dynamic and static characteristics of the material when irradiated with polarized light. It can be shown that the optical storage effect in these materials can be described as a photooptical induced rotational diffusion. The theory is able to describe phenomena which has been found earlier by our group.
Semiempirical quantum mechanical MNDO-calculations were performed on side chain liquid crystalline polymers to predict their electronic properties and thus their anisotropic dielectric and optical properties. These predictions are compared with the corresponding experimental results. The conclusion is that the predictions are sufficiently accurate, which suggests to use such methods for screening potentially interesting polymer liquid crystals prior to synthesizing them.
SummaryLow molar mass and polymeric liquid crystals display extremely large electro-optical and nonlinear optical responses, due to a combination of orientational long range order and fluidity. These responses are controlled on the one hand by the intrinsic anisotropic dielectric and optical properties of these phases and on the other hand by their peculiar curvature elastic and viscous properties.Polymeric liquid crystals, although having the disadvantage of longer response times, offer the advantage that the liquid crystalline state and any modulation imposed on it can be frozen in in a glassy state. Polymeric liquid crystals can thus be used in various applications related to the control of light propagation, optical information storage and the manufacturing of holographic optical elements.Vortrag anlaplich der Tagung der Fachgruppe "Makromolekulare Chemie" der Gesellschaft Deutscher Chemiker Gber "Polymere und Licht in Bad Nauheim vom 7 . bis 9. Mai 1990
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.