Mechanism of electric-field-induced segregation of additives in a liquid-crystal host

Abstract

The mechanism for electric-field-induced segregation of additives, containing a polar group, in a host liquid crystal is proposed. It is shown that the polarity of an applied dc electric field, or the frequency of an ac electric field, strongly influences the segregation of reactive monomers containing an ester group. An explanation of this result is offered based on the association of dissolved ions with polar groups of the reactive monomers. This association is considered to cause these types of additives to drift to the cell surface in the presence of an external electric field. The described mechanism can be applied to the segregation of a broad range of additives in a liquid-crystal host.

Large range electrically-induced reflection notch tuning in polymer stabilized cholesteric liquid crystals

“…19 Commercial liquid crystal mixtures contain ionic impurities (10 9 -10 14 ions per cm 3 ), which might come from synthetic and/or purification steps (catalysts, salts, moisture, and dust), alignment layers, 34 and/or degradation of the LC molecules. [35][36][37][38] Application of a DC bias to PSCLCs exhibiting so-called ''structural chirality'' will act upon the native ionic impurities in the mixture 39-42 that are trapped on or within the polymer stabilizing network.…”

Synthesis of Polyaniline Nanowires and Nanorods in the Presence of NaF under an Electric Field and Their Characterization

“…These studies indicate the application of the electric field is a powerful way to manipulate the structures of the system, which can lead to interesting pattern formation and the realignment of the molecules. On the other hand, the external electric field can facilitate the segregation of reactive monomers to the surface, providing an improved surface director alignment method . At present, electric fields have been applied to the polymerization of α‐methylstyrene, 1,3‐dioxolane, and other ionic polymerization, but has not been introduced into the synthesis of PANI.…”

Electrically Induced Color Changes in Polymer‐Stabilized Cholesteric Liquid Crystals

“…It is well-known that liquid crystal mixtures contain low concentrations of ionic impurities (10 11 -10 13 ions/cm 3 ) [31][32][33][34] and that these mobile charges can have dramatic effects on LCs in response to DC fi elds. The refl ection wavelength red tunes to the positive electrode side, while a small remnant peak blue tunes out of band to the negative electrode side.…”