Photocontrollable induction of supramolecular chirality in achiral side chain Azo-containing polymers through preferential chiral solvation

Abstract

Here we designed a trans–cis photoisomerizable achiral side chain azobenzene-containing polymer, poly(6-[4-(4-methoxyphenylazo) phenoxy] hexyl methacrylate) (PAzoMA), to investigate the possibility of transferring chirality of chiral solvent molecules to polymers. Preferred chirality in supramolecularly assembled trans-azobenzene units of PAzoMA is successfully induced by limonene chirality. This chiral solvation induced chirality arises from superstructural chirality of well-assembled achiral azobenzene units in polymer side chains. The intense bisignated circular dichroism (CD) signals in the UV-vis region disappeared when trans–cis photoisomerization of PAzoMA occurred with 365 nm light irradiation. The polymer aggregate solution shows the CD-silent state when the cis-PAzoMA solution is subjected to 436 nm light irradiation. The intense CD signals with a ∼40 nm red-shift were recovered by heating the polymer aggregate solution to 60 °C and keeping it at this temperature for 40 min, then cooling it down to room temperature. The successful construction of a reversible chiral–achiral switch based on an achiral azobenzene-containing side chain polymer will open a new approach for production of chiroptical materials.