Synthesis and Photoisomerization of Optically Active 1,4-Polyketones Substituted by Azobenzene Side Chains

Abstract

Photoresponsive γ-polyketones substituted by azobenzene side chains were synthesized via asymmetric alternating copolymerization of the corresponding R-olefins in the presence of the Pd-(R,S)-BINAPHOS complex. 13 C NMR of the polyketone having a tetramethylene spacer between the backbone and the azobenzene moiety disclosed that both ketone and spiroketal units existed in chloroform and that the spiroketal unit was transformed back to a ketone unit upon dissolution in 1,1,1,3,3,3-hexafluoro-2-propanol. Conformation of the polymer containing only ketone units was not affected by trans-cis photoisomerization of the side-chain azo chromophore, whereas the corresponding ketone/spiroketal polymer drastically changed its main-chain conformation upon trans-to-cis photoisomerization, as evidenced by increase of CD intensity by 70% at a carbonyl region.

Synthesis of Well-defined Carbazole Group Labelled Polymer via RAFT Polymerization and Study on the Optical Properties

“…8). From the results of reported papers, the typical absorption of azobenzene attached to usual polymer was under 400nm [27][28][29][30]. In Fig.8, a new absorption at round 480 nm suggested azobenzene had attached to the carbazole group at the end of PMA.…”

Use of multislice CT for the evaluation of emergency room patients with chest pain: The so‐called “Triple rule‐out”

“…The photomodulation of the chiroptical properties of optically active polymers has been the subject of intensive research because of the potential applications of these materials in chiroptical switching and reversible optical storage 1, 2. Changes in the chiroptical properties [optical activity and circular dichroism (CD)] induced by irradiation with unpolarized light have been observed in various polymers, such as polypeptides,3, 4 polyisocyanates,5–7 polymethacrylates,8–10 polyaramides11, 12 and polyketones13 functionalized with chromophores (e.g., azobenzene groups) and chiral groups. The geometric change induced by the isomerization of the azobenzene chromophore produces in some cases conformational changes in the polymer backbone.…”

Stimuli-responsive conjugated polymers. Synthesis and chiroptical properties of polyacetylene carrying l-glutamic acid and azobenzene in the side chain

“…The photo-induced circular dichroism (CD) can be erased by heating the films above the clearing temperature of the polymer liquid crystals or by annealing the films. Nozaki and coworkers have synthesized optically active g-polyketones with azobenzene side chains by the asymmetric alternating copolymerization of azobenzene-substituted a-olefins and carbon monoxide [7]. The polyketones change the conformation of the main chain upon trans-cis photoisomerization of the azobenzene moieties.…”