Stable Holographic Gratings with Small-Molecular Trisazobenzene Derivatives

Abstract

We present a series of small-molecular trisazobenzene chromophores, including, for instance, 1,3,5-tris{[4-[4-[(4-cyanophenyl)azo]phenoxy]butyryl]amino}benzene that feature a remarkably stable light-induced orientation in initially amorphous thin-film architectures. It is demonstrated that for optimal performance it is critical to design chemical structures that allow formation of both an amorphous and a liquid-crystalline phase. In the present approach, the liquid-crystalline feature was introduced by inserting decoupling spacers between a trisfunctionalized benzene core and the three azobenzene moieties, as well as adding polar end groups to the latter. To compensate for the deleterious reduction of the glass transition temperature associated with the spacers in the compounds, polar units were incorporated between the benzene core and the side groups. Intriguingly, the molecular glasses that feature a latent liquid-crystalline phase display a remarkable "postdevelopment", i.e., an increase of the amplitude of refractive index modulation in holographic experiments after writing of optical gratings is arrested, exceeding 20% for the previously mentioned derivative. Thus, these nonpolymeric, azobenzene-containing compounds presented in this work appear to be attractive candidates for fabrication of stable holographic volume gratings.

Halogen-Bonded Photoresponsive Materials

“…The rod-like dimeric complex, formed thanks to a highly directional halogen bond, indeed exhibited a hightemperature monotropic nematic LC phase (I 405 N 387 K; see Fig. 8a), which in turn should promote photoalignment [58,59]. The existence of halogen bonding was confirmed by X-ray diffraction and infrared and X-ray photoelectron spectroscopies [12].…”

“…Prior to irradiation, the molecular alignment is random, but excitation with linearly polarized light causes the molecules to align preferentially in the direction perpendicular to the polarization plane, which is seen as an increase in A⊥. The efficient photoalignment of 6 can be attributed to its high-temperature liquid crystallinity [59]. As mentioned above, the halogen-bonded supramolecular complex 6 exhibits not only efficient photoalignment capability, but is also able to form SRGs upon interference irradiation [12].…”

Tuning the optical emission of MoS2 nanosheets using proximal photoswitchable azobenzene molecules

“…The HS-C 6 AZO-Cl was synthesized as reported in literature. 26,27 The mSAM in this case is defined as mSAM-Cl.…”

Supramolecular design principles for efficient photoresponsive polymer–azobenzene complexes

“…93,102,103 For triazine-based molecular glasses, an analogous stabilization effect was attributed to liquid-crystalline character. 104 For the complexes of Pan et al,…”