Helically π-Stacked Conjugated Polymers Bearing Photoresponsive and Chiral Moieties in Side Chains: Reversible Photoisomerization-Enforced Switching Between Emission and Quenching of Circularly Polarized Fluorescence

Novel multifunctional conjugated polymers, [poly(p‐phenylene)s and poly(bithienylene‐phenylene)s with (R)‐ and (S)‐configurations], which have fluorescence, chirality, and photoresponsive properties, have been designed and synthesized. The polymers are composed of π‐conjugated main chains, where poly(p‐phenylene) and poly(bithienylene‐phenylene) are fluorescence moieties, and the side chains of the photochromic dithienylethene moiety are linked with chiral alkyl groups. The polymer films exhibit right‐ or left‐handed circularly polarized fluorescence (CPF) and also show reversible quenching and emitting behaviors as a result of photochemical isomerization of the dithienylethene moiety upon irradiation with ultraviolet and visible light. This is the first report realizing the reversible switching of CPF using chirality and photoresponsive properties. Multifunctional conjugated polymers bearing fluorescent, chiral, and photoresponsive functions are synthesized by introducing dithienylethene moieties linked with optically active alkyl groups into the side chains of poly(p‐phenylene) and poly(bithienylene‐phenylene). Dynamic quenching and emission of circularly polarized fluorescence (CPF) are realized through reversible photoisomerization between open and closed forms of the side chains.