Kinetics of photochemical processes n photochromic azobenzene derivatives. Effect of matrix and of the phase stability

• Autorzy: Janus K. , Matczyszyn K. , Sworakowski J.
• Konferencja: 4 International Conference on Electronic Processes in Organic Materials ICEOPOM-4, Liv, Ukraine, 3-8 June, 2002
• Języki publikacji: EN

Abstrakty

EN

The contribution discusses the effect of environmental constraints on the kinetics of photochromic processes occurring in two groups of azobenzene derivatives: azobenzene-containing crown ethers dissolved in various polymer matrices, and para-disubstituted azobenzenes dissolved in liquid-crystalline matrices. In the azobenzene-containing crown ethers, the presence of the crown is expected to affect the isomerisation kinetics. The experiments demonstrated that the crown create constraints which modify the molecular structure, thus influencing the isomerisation kinetics as was indeed found in our experiments. In the shortest crown, the room-temperature rate constant of the thermal isomerisation is c.a. two orders of magnitude lower than the respective rate in the parent azobenzene. Measurements of the kinetics of isomerisation of photochromic 4-fluoro-4?-methoxyazobenzene dissolved in the liquid-crystalline pentylocyanobiphenyl (5CB) were carried out. Deviations from the expected Arrhenius behaviour were observed for the thermal cis-trans reaction near the phase transition temperature of 5CB (308 K). It was also found that the isomerisation reaction may trigger the nematic-to-isotropic phase transition at the temperature substantially lower than the thermodynamic transition temperature.

Słowa kluczowe

EN

photochromism; azobenzene derivative; kinetics

• Wydawca: Oficyna Wydawnicza Politechniki Wrocławskiej
• Czasopismo: Materials Science
• Rocznik: 2002
• Tom: Vol. 20, No. 3
• Strony: 45--55
• Opis fizyczny: Bibliogr. 24 poz.,

Twórcy

autor

Janus K.

autor

Matczyszyn K.

autor

Sworakowski J.

• Institute of Physical and Theoretical Chemistry, Wrocław University of Technology, Wybrzeże Wyspiańskiego 27, PL-50-370 Wrocław 51, Poland