Synthesis and characterization of two chiral azobenzene-containing copolymers

Two copolymers, poly{4'- [ [ [2-(methacryloyloxy)ethyl] ethyl] amino] -4-nitroazobenzene} -co[(methacryloyloxy)-4-nitrophenyl-(S)-prolinol] (poly(DR1M-co-(S)-NPPMMA)) and poly{4-[2-methacryloyloxy)ethyl]azobenzene-co-[(methacryloyloxy)-4-nitrophenyl-(S)-prolinol] (poly(MEA-co-(S)-NPPMMA)), were synthesized and characterized. They contain side chain azobenzene chromophores (DR1 and MEA, respectively) and a prolinol-based chiral side chain group (NPP). Photoinduced birefringence, polarized absorption spectroscopy, and chiroptical properties (optical rotation and circular dichroism) in films were measured, and the results are discussed in relation to the structure of these copolymers. Cooperative motion of the chiral structural unit is observed for the photoinduced birefringence. Chirality is, however, not transmitted from the chiral structural unit to the azobenzene structural unit at the 1:1 compositions investigated here.