Unpolarized-Light-Driven Amplified Chiroptical Modulation Between Chiral Aggregation and Achiral Disaggregation of an Azobenzene-alt-Fluorene Copolymer in Limonene

A trans-cis photoisomerizable achiral polymer, poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-4,4'-azobenzene] (F8AZO), was designed. The chirality of (S)- and (R)-limonene used as a solvent allowed for the generation of optically active F8AZO aggregates, revealing intense circular dichroism (CD) signals in the visible region. The reversible chiroptical response was achieved upon alternating photoirradiation at 405 nm (trans-form) and 546 nm (cis-form). This ability originated from the switching between the trans-origin aggregation and cis-origin disaggregation of F8AZO in the limonene-2-propanol-chloroform tersolvent.