摘要：

4-Nitrophenyl 4-[[2-[(2-methyl-1-oxo-2-propenyl)oxy]ethyl]oxy]benzoate (BEM) was synthesized and copolymerized with 4'-[[[2-[(2-methyl-1-oxo-2-propenyl)oxy]ethyl]ethyl]amino]-4-nitroazobenzene (DR1M) in dioxane at 60 °C. BEM and DR1M copolymerize in a random fashion with reactivity ratios rDR1M = 0.82 and rBEM = 1.03. The copolymers are amorphous. Interactions between the azo and the BEM side groups produce a shift of absorption maxima in the electronic spectra. Birefringence can be photoinduced and photoerased on films of all copolymers. The photoinduced birefringence per azo chromophore is very high in copolymers with low azo contents, about 4 times that of poly(DR1M). A cooperative motion of BEM groups with the azo groups is postulated as the reason for the additional birefringence. To our knowledge this is the first example of cooperative motion in amorphous polymers. The growth and relaxation of the birefringence are fitted by biexponential equations and "writing" rate constants are calculated for tw...

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