Synthesis and photoinduced transformation of helical aromatic polyamides containing atropisomeric biphenylene units and azobenzene segments in the main chain

Optically active helical polyamides were synthesized by condensation of axially dissymmetric (R)- or (S)-6,6′-diamino-2,2′-dimethylbiphenyl with aromatic dicarbonyl chlorides. The wholly aromatic polyamides obtained were soluble in various low-polarity organic solvents such as tetrahydrofuran and chloroform, as well as in polar N,N-dimethylacetamide. Excellent thermal stability of the helical structure was observed for the polyamide obtained with 4,4′-dicarbonylbiphenyl chloride in refluxing N,N-dimethylacetamide. Chiroptical data obtained from the circular dichroism spectra showed that the helical conformation of the polyamide containing azobenzene segments in the main chain can be transformed reversibly on irradiation with UV–visible light because of the trans–cis isomerization of the segments. Copyright © 2004 Society of Chemical Industry