Photomodulation of the Mechanical Properties and Photo-Actuation of Chitosan-Based Thin Films Modified with an Azobenzene-Derivative

A sophisticated comprehension of the impacts of photoisomerization and photothermal phenomena on biogenic and responsive materials can provide a guiding framework for future applications. Herein, the procedure to manufacture homogeneous chitosan-based smart thin films are reported by incorporating the light-responsive azobenzene-derivative Sodium-4-[(4-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)phenyl)diazen-yl]-benzenesulfonate (TEGABS) in the biopolymer through electrostatic interactions. When irradiated with UV-light the TEGABS/chitosan films show a biresponse, comprising the E→Z photoisomerization with a half-life of 13 - 20 h and the light-induced evaporation of residual moisture leading to an increase in the reduced indentation modulus (up to 49%) and hardness. Freestanding films of TEGABS/chitosan show actuation up to 13° while irradiated with UV-light. This work shows the potential of biogenic polysaccharides in the design of biresponsive materials with photomodulated mechanical properties and unveils the link between the humidity of the environment, residual moisture, and the photomodulation of the mechanical properties.

A DFT study on the isomerization mechanism of azobenzene derivatives on silicon substrates

The cis–trans isomerization mechanism of azobenzenesulfonamide derivatives on silicon substrates was investigated using DFT. The most favorable cooperative mode of the N2 inversion of the L followed by the N1 inversion of the R was proposed.

Hetarylazopyrazolone Dyes Based on Benzothiazole and Benzimidazole Ring Systems: Synthesis, Spectroscopic Investigation, and Computational Study

In this study, the synthesized coupling component 1-(2-benzothiazolyl)-3-methylpyrazol-5-one reacted with diazotised heterocyclic amines to afford six novel hetarylazopyrazolone dyes. These azo dyes based on benzothiazole and benzimidazole ring systems were characterized by spectral methods and elemental analyses. The solvatochromic behaviors of these dyes in various solvents were evaluated. The ground state geometries of the dyes were optimized using density functional theory (DFT). Solvent, acid-base, and substituent influences on the wavelength of the maximum absorption were examined in detail. Time-dependent density functional theory (TD-DFT) calculations were performed to obtain the absorption spectra of the dyes in various solvents and the results compared with experimental values. Besides, frontier molecular orbitals (FMO) analysis for the dyes is also described from the computational process.