Liquid crystalline phases in suspensions of pigments in non-polar solvents

Klein, Susanne; Richardson, R. M.; Eremin, Alexey

Abstract

We will discuss colloid suspensions of pigments and compare their electro-optic properties with those of traditional dyed low molecular weight liquid crystal systems. There are several potential advantages of colloidal suspensions over low molecular weight liquid crystal systems: a very high contrast because of the high orientational order parameter of suspensions of rod shaped nano-particles, the excellent light fastness of pigments as compared to dyes and high colour saturations resulting from the high loading of the colour stuff. Although a weak `single-particle' electro-optic response can be observed in dilute suspensions, the response is very much enhanced when the concentration of the particles is sufficient to lead to a nematic phase. Excellent stability of suspensions is beneficial for experimental observation and reproducibility, but it is a fundamental necessity for display applications. We therefore discuss a method to achieve long term stability of dispersed pigments and the reasons for its success. Small angle X-ray scattering was used to determine the orientational order parameter of the suspensions as a function of concentration and the dynamic response to an applied electric field. Optical properties were investigated for a wide range of pigment concentrations. Electro-optical phenomena, such as field-induced birefringence and switching, were characterised. In addition, mixtures of pigment suspensions with small amounts of ferro uids show promise as future magneto-optical materials.

• Publication Date: Dec 10, 2016
• Deposit Date: Jan 19, 2018
• Publicly Available Date: Jan 22, 2018
• Peer Reviewed: Peer Reviewed
• Pages: 847-870
• Series Title: Series in Soft Condensed Matter
• Series Number: 7
• Book Title: Liquid Crystals with Nano and Microparticles
• Chapter Number: 26
• ISBN: 9789814619257
• Keywords: colloidal suspensions, liquid crystals, pigments, birefringence, X-ray scattering, magneto-optical response
• Public URL: https://uwe-repository.worktribe.com/output/902374
• Publisher URL: http://www.worldscientific.com/worldscibooks/10.1142/9280
• Contract Date: Jan 19, 2018