Synthesis and chiroptical properties of optically active photochromic polymers with side-chainL-lactic residues connected totrans-azobenzene moieties bearing a reactive formyl electron-withdrawing group

Abstract

SUMMARY: The synthesis of a novel optically active monomer containing a photochromic chromophore, trans-(S)-4-(2-methacryloyloxypropanoyloxy)-49-formylazobenzene, is described. The monomer was radically homopolymerized and copolymerized with methyl methacrylate to afford the corresponding optically active polymers, which were fully characterized. The chirooptical and conformational properties in solution of the resulting polymers were investigated by circular dichroism and solvatochromism measurements and compared with those of the corresponding low molecular weight model compound, trans-(S)-4-(2-pivaloyloxypropanoyloxy)-49-formylazobenzene, purposely synthesized.

Photoinduction and Control of the Supramolecular Chirality in Liquid Crystalline Azomaterials

“…These exciton couplets are due to the splitting of an H-band as a consequence of a chiral interaction between adjacent chromophores [27][28][29]. The Cotton effect at 390 nm can be due to the superposition of the band of the exciton couplet centered around 330-340 nm, the induced Cotton effects of the isolated azobenzene units and J-aggregates [30]. The exciton couplet associated to chiral H-aggregates was presented in the CD spectra of all irradiated azopolymers.…”

Optically active polymers bearing side-chain photochromic moieties: synthesis and chiroptical properties of methacrylic homopolymers with pendanttrans-azobenzene chromophores bound throughL-leucine,L-valine andL-proline amino acid spacers

“…Moreover, as far as the pep* electronic transition is concerned, a shift of the absorption band towards higher wavelengths is observed in all polymers passing from CHCl 3 to THF, i. e. on increasing polarity and donor character of the solvent, [20] analogously to what reported in similar polymers. [4,5,7] All low and high molecular weight compounds in the trans configuration display in chloroform solution optical activity of negative sign at the sodium D-line (Tab. 3).…”

“…[4][5][6][7] Indeed, optically active photochromic (meth)acrylic homopolymers, [poly(MLA) and poly(ALA)] (Chart 1), characterized by a L-lactic acid residue between the backbone and the trans-azobenzene chromophore, display strong CD couplets in the spectral region related to the p e p* electronic transition of the azobenzene moiety in trans configuration. [4] .…”

“…[7] Finally, the low molecular weight structural models of all the above polymeric systems, such as trans-(S)-4-(2-pivaloylamino-4-methylpentanoylamino)azobenzene [PLEA], trans-(S)-4-(2-pivaloylamino-3-methylbutanoylamino)azobenzene [PVA] and trans-(S)-4-N-pivaloyl-2-pyrrolidinoylamino)azobenzene [PPA] (Charts 2 and 3, respectively) have been also prepared.…”

Main chain helical transformation induced through UV light in arylidene polymer

“…Though the acrylated polymers having side chain azobenzene chromophore showing a definite helical conformation was reported by several research workers [3][4][5][6][7], there are only a few reports available about the circular anisotropy was induced by the circularly polarized light as the source of chirality [3,8]. Also the kinetics of the transformation of the helical reversal was not studied in detail.…”