Photostimulated dilation and contraction

Fig. 17. Photostimulated dilation and contraction of polyacrylamide gel having pendant triphenylmethane leucohydroxide groups (3.7 mol %) with light of wavelength longer than 270 nm at 25 C [43]. Wo is the weight before photoirradiation...

Figure 4.15. Photostimulated dilation and subsequent contraction of the polyacrylamide gel containing different percents of hydroxy triphenymethane pendant groups (a) 3.7% (b) 9%(UV irradiation (k = 270 nm at 250 C, [90].

A disk-shaped gel (10 mm in diameter and 2 mm in thickness) with 3.7 mol% triphenylmethane leucohydroxide residues showed photostimulated reversible dilation in water. Figure 27 shows that on UV irradiation ( > 270 nm), the gel swells and the weight increases by as much as three times its original weight in 1 h. The dilated gel contracts in the dark to its initial weight in 20 h. The cycles of expansion and contraction of the gel were... 

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