The principle of a new electrochromic display based on an oxidation-reduction reaction of an organic compound of the viologen family is described. The result is a display having a built-in memory, high contrast, a low switching voltage, and a low mean power consumption.

Silica gel and Cab-O-Sil were chemically modified (silylated) with 3-aminopropyltriethoxysilane and 3-methacryloxypropyltrimethoxysilane under carefully controlled conditions. Subsequently the products were investigated by elemental analysis, Fourier transform IR spectroscopy, and 13C and 29Si crosspolarization magic angle spinning NMR (CP-MAS NMR). The influence of the reaction conditions of the silylation and the effect of subsequent heat treatment and water addition were studied. The resulting differences shed new light on the combined effects of reaction conditions and silica surface structures on the course of the reactions. Some assignments of 29Si NMR signals to specific structures were confirmed, while in one case a reassignment was proposed.

Electrochemical reactions that produce a change of light absorption in the visible region can be used in display devices. The reduction of the 4,4'‐di‐pyridinium compounds or viologens to stable blue radicals is very promising in this respect. It was found that in aqueous solution the solubility of the radical is remarkably lower than that of the oxidized form. It turned out that the solubility depends on the kind of anion and the magnitude of the viologen radical ion.