Optically Active Photochromic Polymers with Three-Arm Star Structure by Atom Transfer Radical Polymerization

Macrocycle-based topological azo-polymers: facile synthesis and unusual photoresponsive properties

Macrocycle-based topological azo-polymers with unusual photosensitive properties were synthesized via a selective acyclic diene metathesis polymerization of different monomers using an acrylate-functionalized cyclic azo-polymer as a chain stopper prepared from a linear precursor by “click” cyclization reaction, which will open a new perspective in photoinduced materials.

Synthesis and chiroptical properties of chiral azoaromatic dendrimers with a C3-symmetrical core

New chiral azoaromatic dendrimeric systems have been synthesized starting from 1,3,5-benzenetricarbonyl trichloride as the core molecule. The simultaneous presence of the (S)-3-hydroxy pyrrolidinyl ring as the optically active moiety and the azobenzene donor-acceptor conjugated system as the photochromic group with permanent dipole moment, makes these systems potentially interesting as materials for advanced applications in nanotechnologies. All the compounds obtained have been characterized with particular attention to the effects induced by changing the electron-withdrawing group in the chromophoric moiety and to their optical activity. A strong nonlinear enhancement of chiroptical properties related to the number of chiral units linked to the symmetrical core is observed in these derivatives, which indicates the presence of conformationally chiral substructures.

Supramolecular chirality from an achiral azobenzene derivative through the interfacial assembly: effect of the configuration of azobenzene unit

The Langmuir-Schaefer (LS) films of an achiral azobenzene derivative, 4-octyl-4'-(5-carboxypentamethyleneoxy) azobenzene (C8AzoC5), were fabricated and their optical activities were investigated. It was found that the LS film of the trans-C8AzoC5 showed strong Cotton effect, while that of cis-C8AzoC5 did not. The characterization of the LS films by UV-vis, Fourier transform infrared (FT-IR) spectra, and X-ray diffraction (XRD) revealed that this interesting phenomenon was due to the different packing of the azobenzene unit in the LS film. The planar conjugated trans-azobenzene favored ordered cooperative packing in a helical sense and produced the supramolecular chirality, while the cis-isomer did not due to the bulky twisted configuration.