ISBN 9783843936026

978-3-8439-3602-6, Reihe Physikalische Chemie

Matthias Kundt
Magnetoresponsive liquid crystalline systems based on elongated core-shell particles in nematic phases

219 Seiten, Dissertation Universität Köln (2017), Softcover, A5

Zusammenfassung / Abstract

In 1970 Brochard and de Gennes predicted that the combination of magnetic nanoparticles and a liquid crystalline matrix results in a hybrid material that is highly sensitive towards the manipulation by a magnetic field. It has also been predicted that such a material shows remarkable properties due to the combination of an anisotropic, ordered matrix and magnetic particles resulting in an orientational coupling between the matrix material and the magnetic dopants.

In this work, hybrid liquid crystalline systems with a boosted magnetoresponse are realized by doping of 4-cyano-4'-pentylbiphenyl (5CB) with magnetic, spindle-like hematite particles, surface-functionalized with a polysiloxane-based side-chain liquid crystalline polymer. High functionalization degrees of the attached stabilizers are reached.

A positive impact of the dopants on the physical properties of 5CB is indicated by the increased order parameter of the particle/LC hybrid systems. New ways to surface-functionalized spindle-like hematite particles are presented in this work. Stable particle dispersions in 5CB with an increased particle concentration are obtained. A model system is developed that allows to effectively increase the stability of inorganic particles in a liquid crystalline matrix, enhance the order parameter of the hybrid system and boost the sensitivity to external magnetic fields.