Controlled Synthesis Of Cyanostilbene-Functionalized Helical Polydiacetylene

Polydiacetylene(PDA)is a kind of unique linear π-conjugated polymers,which has been widely researched in the conjugated polymers family due to their peculiarity of preparation methods,molecular structure and output signal.Cyanostilbene(CNBE)derivatives as conjugated organic emitting materials have received a great deal of attention due to the attractive dual-functions of fluorescence and photoisomerization properties with a phenomenon of aggregation induced emission enhancement(AIEE).In this paper,the main goal is to fully utilize the different photo-functional groups on an individual molecule for the preparation of tunable multifunctional thin flms.We designed and synthesized a dual photo-functionalized compound(abbreviated as(Z)-CNBE-DA)combined a photo-isomerizable CNBE unit with a photo-polymerizable diacetylene for the first time.This compound can self-assemble to form a low ordered liquid crystalline phase and a highly ordered crystalline phase with a wide mesophase temperature range of about 87 ℃,showing the characteristics of AIEE.Helical PDA backbone could be formed upon irradiation with circularly polarized ultraviolet light(CPUL)because of intermolecular ordered and close packing arrangement origined from strong intermolecular π-π interactions of(Z)-CNBE-DA molecules.The spiral PDA films exhibit reversible thermochromism within the scope of heat treatment at 80℃ and the chiral signal is maintained when heated to the red phase from the blue.However,the(Z)-CNBE-DA exhibits interesting Z-E isomerization to form bent-shaped(E)-CNBE-DA molecules upon irradiation of 365 nm UV light,breaking the order of the molecule,displaying no liquid crystalline properties.The(E)-CNBE-DA molecules self-assemble into irregular loose packing,inhibiting the formation of helical PDA chains upon CPUL irradiation.This work is mainly triggered by light to regulate the molecular packing arrangement at the molecular level,making diacetylene derivatives produce different polymerization behavior,controlling molecules to produce a variety of orderly structure,such as liquid crystal,supramolecular,and chiral assemblies,thus realize the preparation of optically adjustable multifunctional films.