Electrooptical properties of liquid-crystalline physical gels: a new oligo(amino acid) gelator for light scattering display materials

Abstract

Nematic liquid-crystalline (LC) physical gels suitable for light scattering electrooptical displays have been prepared from a nematic liquid crystal and a low molecular weight gelator containing an oligo(L-isoleucine) moiety. The number of amino acid moieties of the gelators has a great effect on the gelation ability and electrooptical behaviour of the LC gels. A gelator having three L-isoleucine moieties forms LC gels most efficiently. The use of the gelator leads to microphase separation where fibres with a diameter of ca. 30 nm finely disperse in liquid crystals. Such structures are suitable for the induction of high light scattering. The light scattering states are electrically switched to transparent states in liquid crystal cells. The contrast of light transmittance and driving voltages are improved by the tuning of the gelator concentrations. A gelator having two L-isoleucine moieties exhibits poor gelation ability. A mono-amino acid gelator forms LC gels showing lower light scattering, although they are applicable to twisted nematic mode.