New multifunctional sulfonamide-containing azobenzene chromophores: Synthesis and photochromic properties

The work presents synthesis and characterization of novel sulfadimethoxine and sulfabenzamide azo derivatives as well as the kinetic study of their trans–cis–trans isomerization. Spectral properties and kinetic constants were determined for the chromophores dispersed in poly(methyl methacrylate-co-butyl methacrylate) deposited on glass substrates in form of transparent, thin films. The maximum absorption bands were observed within wavelength in range of 446–457 nm for N-disubstituted aminoazobenzene derivatives and 361–362 nm for phenolic chromophores. For the phenolic azo derivatives of sulfadimethoxine and sulfabenzamide the photoisomerization induced with UV light followed the first order kinetics, while for other compounds the process combined of two parallel reactions with different rate constants was observed. The rate constants of thermal relaxation in the dark were usually few times smaller than those determined for photoinduced trans–cis isomerization. The change of real part of refractive index upon illumination determined by ellipsometry was within the range of 0.0043–0.0138.

► New photochromic azo dyes containing sulfonamide groups. ► Photochromic behavior of the dyes. ► Kinetic studies of trans–cis isomerization and thermal relaxation. ► Refractive index modulation under illumination, ellipsometric measurements.