Optically active polymers bearing sidechain photoreactive moieties: copolymers of racemic 4-acryloyloxy- α-methylbenzoin methyl ether with (−)-menthyl acrylate

Abstract

Optically active copolymers of racemic 4-acryloyloxy- α -methylbenzoin methyl ether (AMBE) with (−)-menthyl acrylate (MtA) have been radically prepared. The reactivity of the comonomers suggests that the copolymers display a certain tendency to an alternating distribution of the co-units. Optical activity at 589 nm of the copolymers seems to exclude any stereoselectivity and stereoelectivity during the copolymerization process. Chiroptical properties indicate that an induced optical activity on benzoin methyl ether chromophores occurs. Circular dichroism (c.d.) data, connected with n→π * and π→π * electronic transitions of the benzoin methyl ether moiety, suggest that the observed ellipticity is substantially due to isolated AMBE units. C.d. features indicate that the macromolecules, due to the presence of optically active MtA co-units, assume conformations with a prevailing handedness for sections not sufficiently long to provide cooperative interactions between side-chain benzoin methyl ether chromophores disposed along the backbone with a mutual chiral geometry suitable for exciton couplings.