Microgel particles of poly(2-vinylpyridine) cross-linked with 0.5wt% divinylbenzene were synthesized. Due to differences in the scattering of light, a dispersion of the particles appears opaque milky white above pH 4.5 and transparent below pH 4.5. The pH of a 0.15wt% dispersion was modified using a poly (aniline) film as a source/sink of protons and a Ag/AgCl electrode as a source/sink of chloride counterions. The absorption of the sample at 400 nm was typically reduced from c.a. 3.5 to c.a. 0.5 in less than 20 minutes and increased to c.a. 3.2 in less than 20 minutes. This system could form the basis for a new type of display device, but it is insufficiently fast or consistent in its current form.
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