Azo polymers for reversible optical storage. 8. The effect of polarity of the azobenzene groups

Abstract

Poly[4′-[[(2-methacryloyloxy)ethyl]ethylamino]azobenzene] (pMAEA) was prepared. Its reversible optical storage properties were studied and compared with the properties of previously reported poly[4-(2-methacryloyloxy)ethylazobenzene] (pMEA) and poly[4-nitrophenyl-4′-[[2-(methacryloyloxy)ethyl]ethyl-amino]phenyldiazene] (pDR1M). The effect of the dipole moment of the azobenzene moiety on the optical storage properties was studied by comparing the photochemically induced birefringence "writing" and "relaxation" behaviors. The writing and relaxation rates are both in the order pDR1M > pMAEA > pMEA. In addition, pDR1M, which contains donor/acceptor substituents in the azobenzene side chain, exhibits the highest saturation level of optically induced birefringence. The fraction of birefringence conserved after relaxation is lowest for pMEA, which has no donor/acceptor substituents in the azobenzene side chain, and highest for pDR1M. Keywords: polymers, azobenzene type, birefringence, photochemically induced orientation, reversible optical storage.