Preparation and optical properties of an all-polymer light modulator using colored N-isopropylacrylamide gel particles in a gel-in-gel system

A novel all-polymer light modulator with a gel-in-gel system was developed. The gel-in-gel system was constructed with colored gel particles responsive to stimuli held independently in another stimuli-nonresponsive gel matrix. Well-known thermoresponsive N-isopropylacrylamide (NIPAM) gel particles containing a pigment were dispersed and fixed in an outer stimuli-nonresponsive gel matrix. When poly(vinyl alcohol)-styrylpyridinium (PVA-SbQ) was used for the outer gel matrix, the light modulator showed excellent color-changing properties because the PVA-SbQ matrix was selectively formed around the NIPAM gel particles and the particles exhibited a large volume change in the matrix. The temperature when the outer gel matrix was formed affected the haze of the light modulator. When the outer gel matrix was formed in the swollen state of the NIPAM gels, the haze of a light modulator increased with heating. On the contrary, the haze of a light modulator prepared in the shrunken state of the NIPAM gels decreased with heating. The response time of the color change was less than 1 s. The gel-in-gel system made a very fast macroscopic color change, taking advantage of the fast response of the micrometer-sized gel particles. We believe that a light modulator with a gel-in-gel system may find various applications in optical devices. (c) 2006 Wiley Periodicals, Inc.