Color effects with colloidal silica

Takagi et al. reported the intercalation of l, 3, 3 -trimethylspiro[2//-l-benzopyran-2,2 -indoline] (H-SP) and its 6-nitto (NO2-SP) and 6-nitro-8-(pyri-dinium)-methyl (Py+-SP) derivatives into montmorillonite their photochromic behavior (the photochromic reaction of spiropyran is shown in Fig. 22) has been studied for colloidal systems (208). The effects of intCTcalation on the rate of thermal coloration and decoloration have been compared with those in other systems, such as colloidal silica, hexadecyltrimethylammonium bromide, and sodium dodecylsulfate (SDS) micelles. 

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