Page 105 - Photoreactive Organic Thin Films

84 ZOUHEIR SEKKAT

0.0
400 450
Wavelength, X / nm
FIGURE 3.10 Relaxation in the dark of the dichroism induced by linearly polarized 360 nm light
irradiation in the P 2,io azo-polyglutamate. The spectra were obtained after 2 minutes' unpolarized
450 nm irradiation (I// and IjJ and after 6 days' relaxation in the dark (2// and 2J. Note that the
absorbances have shifted to higher values due to the cis—»trans isomerization, while the initial
dichroism was increased.The inset is an expanded view of of the region around 450 nm. After reference
22, redrawn by permission of ACS.

H -,

PUR-1 (T g »140°)

C
H ft

CN
0
PUR-3 (T g = 13<>) PUR.4 (T g=136°)
FIGURE 3.11 Chemical structures of the Azo-PUR polymers.The polymers' Tgs are indicated.