Unusually fast optically induced birefringence in polyoxetanes bearing 4-(N,N-diphenyl)amino-4′-nitroazobenzene chromophores

Two new polyoxetane polymers bearing azobenzene-type chromophore pendants were prepared, and their photoinduced molecular orientation and relaxation were studied. The two polymers differ in the mode of attachment of the chromophores, which are either laterally (Pox 1) or perpendicularly (Pox 2) bound to the polymer backbone. The two polymers reveal unusually fast (∼2 s to saturation at 0.4 W/cm²) photoinduced reorientation of chromophores and decay behavior at room temperature. Side-on attachment of the chromophores (Pox 1) results in a significantly faster response to polarized light and higher maximum birefringence than end-on attachment. The kinetics of photoinduced orientation and relaxation decay were quantitatively analyzed and the results are discussed in relation to the structures of the polymers.