Phenomenology of Photoinduced Processes in the Ionic Sol−Gel-Based Azobenzene Materials

Abstract

Very recently, supramolecular azobenzene-containing materials have been demonstrated to be effective for holographic inscription of surface relief gratings. High efficiency of grating formation in these materials is advantageously combined with easy material preparation because of the supramolecular principle of building blocs combination, availability of chemical components, and good film-forming properties. The materials show great promise for wide optical applications. Here, one type of material formulation based on ionic complexes of poly(aminosiloxane) is experimentally investigated concerning the induction of birefringence, efficiency of relief formation, and thermal stability of surface structures. Properties of the material were changed on the molecular level by varying the azobenzene content and on the macro level by varying chemical processing conditions. The results are discussed in terms of cross-linking and plasticizing effects caused by residual solvent and the low-molecular-weight azobenzene component. An improvement of both the efficiency of grating formation and their thermal stability by these means has been demonstrated. The results can be adapted to other azobenzene-containing materials. In addition, a drastic change of films solubility has been observed upon irradiation.

Optically induced birefringence and holography in silk

“…Optically induced birefringence was measured using a standard pump and probe setup23 with a 1‐mm radius 488‐nm pump polarized at 45° to the horizontal and a probe comprising a circularly polarized 632.8 nm He–Ne laser beam as indicated in Figure 1. After passing through the film, the probe was split into p and s polarization by means of a Wollaston prism.…”

Light-Triggered Formation of Surface Topographies in Azo Polymers

“…These materials allowed for creation of gratings with a topography of 550 nm. Later, Stumpe and co-workers found that the grating formation when utilizing sol-gel techniques is greatly influenced by multiple factors such as cross-linking and plasticizing effects [60]. They also proposed a different ionic supramolecular azobenzene-based material [61].…”

Photochromic supramolecular azopolyimides based on hydrogen bonds

“…Diffraction gratings were inscribed using a holographic setup described elsewhere [59]. An argon laser at wavelength k = 488 nm (Innova 90, Coherent) was used for the grating inscription.…”

“…The hydrogen bonding has led to the shift to the low field although formally the electron density has increased through an interaction with the free electron pair of the acceptor atom. The electric dipole field of the hydrogen bond appears to affect deshielding [59]. Taking into account FTIR spectra of supramolecular systems based on Azo-3, that is, containing pyridine ring, the appearance of the absorption band at 2564 cm À1 would be expected due to the H-bond between nitrogen atom and OH group in polymers, however, this bond is not seen in all assembles (cf.…”