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, liquid crystalline, and photoresponsive functions were synthesized by introducing the dithienylethene moieties into side chains of poly(pphenylene-vinylene) [P1] and poly(bithienylene-phenylene) [P2]. Observation of polarizing optical microscope showed that the polymers have main-chain-type liquid crystallinity. Reversible photoisomerization of the dithienylethene moiety was observed in both solution and cast film. Drastic quenching of fluorescence occurred when the photoresponsive moiety changed from an open form to a closed one upon irradiation of ultraviolet light. The quenched fluorescence was recovered through a photoisomerization from the closed form to the open one. Macroscopically aligned P2 film, prepared by a rubbing in liquid crystalline phase, exhibited a linearly polarized fluorescence with significant anisotropy. Reversible quenching and emitting behavior in anisotropic fluorescence was well controlled by the photochemical switching.

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