Novel optically active methacrylic homopolymers with side-chain l-lactic acid moieties interposed through ester bonds between the main chain and trans-4-azobenzene chromophores bearing in the 4′-position electron withdrawing groups, such as the cyano and nitro residues, have been synthesized and structurally characterized. Investigation by circular dichroism of the chiroptical and conformational properties of the polymers in solution indicates a much higher optical activity of these latter with respect to that of the corresponding low molecular weight model compounds, purposely prepared, due to the presence of dissymmetric conformations of one prevailing handedness. The trans to cis photoisomerization kinetics of the azoaromatic double bond has been measured in solution for polymers and models and the resulting data compared with those of previously reported similar photochromic derivatives. The influence of the nature of the electron withdrawing group in the 4′-position of the azobenzene chromophore on the chiroptical properties of the polymers is also discussed.
Optically active polymethacrylates with side-chain L-lactic acid residues connected to push-pull azobenzene chromophores
CARLINI, CARLO;ALTOMARE, ANGELINA;SOLARO, ROBERTO
2000-01-01
Abstract
Novel optically active methacrylic homopolymers with side-chain l-lactic acid moieties interposed through ester bonds between the main chain and trans-4-azobenzene chromophores bearing in the 4′-position electron withdrawing groups, such as the cyano and nitro residues, have been synthesized and structurally characterized. Investigation by circular dichroism of the chiroptical and conformational properties of the polymers in solution indicates a much higher optical activity of these latter with respect to that of the corresponding low molecular weight model compounds, purposely prepared, due to the presence of dissymmetric conformations of one prevailing handedness. The trans to cis photoisomerization kinetics of the azoaromatic double bond has been measured in solution for polymers and models and the resulting data compared with those of previously reported similar photochromic derivatives. The influence of the nature of the electron withdrawing group in the 4′-position of the azobenzene chromophore on the chiroptical properties of the polymers is also discussed.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
