Azo compound

About: Azo compound is a research topic. Over the lifetime, 2547 publications have been published within this topic receiving 41112 citations.

Surface relief structures on azo polymer films

Abstract: All optical fabrication of Surface Relief Grating (SRG) on azobenzene functionalized polymer films is reviewed in this article. The uniqueness of the single step erasable photofabrication of large amplitude surface relief structures on azo polymer films is mainly due to the photoisomerization and photoanisotropic behavior of the azobenzene group. The design and synthesis of several classes of suitable azobenzene functionalized polymers for the SRG formation is presented. Experimental studies are carried out in a systematic manner to understand the chemical and physical intricacies involved in the SRG formation process. Structural requirements and their limitations for the efficient fabrication of SRGs on azo functionalized polymer films are also discussed. Understanding the fundamental mechanism of SRG formation on the azo functionalized polymer films enables us to make use of these structures in a variety of applications.

Gold-Catalyzed Synthesis of Aromatic Azo Compounds from Anilines and Nitroaromatics

Abstract: The selective formation of aromatic azo compounds at preparative or industrial levels requires stoichiometric amounts of environmentally unfriendly transition metals or nitrites. Here, we show that gold nanoparticles supported on titanium dioxide (TiO2) and nanoparticulated cerium dioxide (CeO2) catalyze the aerobic oxidation of aromatic anilines to aromatic azo compounds with yields above 98% under mild reaction conditions. Gold on TiO2 can also act as a reductive catalyst to access the compound directly from nitroaromatics through a two-step, one-pot reaction. The catalytic process shows promise for efficient synthesis of symmetric aromatic azo compounds, and even a range of asymmetric aromatic azo compounds.

Electric field-induced isomerization of azobenzene by STM

Abstract: The electric field applied between the tip of a scanning tunneling microscope and a metallic surface is shown to induce the reversible trans−cis isomerization of single azobenzene derivatives adsorbed on a Au(111) surface. The investigated molecule is symmetrically equipped with four tert-butyl groups, which decouple the azobenzene core from the metallic surface, facilitating the formation of highly ordered islands. Due to the spatial extension of the electric field, it is possible to switch many molecules within the same island simultaneously.

Preparation of Azobenzene-Containing Amphiphilic Diblock Copolymers for Light-Responsive Micellar Aggregates

Abstract: Diblock copolymers composed of a side-chain liquid crystalline azobenzene-containing polymethacrylate and poly(tert-butyl acrylate) (PAzoMA-b-PtBA) were prepared using atom-transfer radical polymerization (ATRP). After subsequent selective hydrolysis of PtBA yielding poly(acrylic acid) (PAA), amphiphilic diblock copolymers of PAzoMA-b-PAA were obtained. Aggregation of either PAzoMA or PAA block occurs in solvents selective for one of the blocks. Adding water into dioxane solution of PAzoMA-b-PAA forms micellar aggregates due to the hydrophobic PAzoMA block. Under alternating UV and visible light illumination, reversible changes in micellar aggregates, for both core-shell micelles and vesicles, took place as a result of the reversible trans-cis photoisomerization of azobenzene mesogens in PAzoMA.

Synthesis, nanostructures, and functionality of amphiphilic liquid crystalline block copolymers with azobenzene moieties

Abstract: A series of liquid crystalline (LC) homopolymers of poly{11-[4-(4-butylphenylazo)phenoxy]undecyl methacrylate}containing an azobenzene mesogen with different degrees of polymerization were synthesized by using the atom transfer radical polymerization (ATRP) method. The homopolymers were prepared with a range of number-average molecular weights from 6100 to 23 500 with narrow polydispersities of less than 1.17. Thermal investigation showed that the homopolymers exhibit monolayer smectic A, smectic C, and an unknown smectic X phases. The transition temperatures increase slightly with the increase of the molecular weights and level off at around 21 500. Novel amphiphilic LC-coil diblock copolymers with a defined length of a flexible poly(ethylene glycol) segment as the hydrophilic coil were also prepared by the ATRP method. The LC-coil diblock copolymers exhibit narrow polydispersities of less than 1.11. Morphologies of the thin films of the block copolymers were investigated by using transmission electron m...