Thermodynamic model of phase transitions induced by cis-trans thermal- and photo-isomerization of azobenzenes

EZEQUIEL R. SOULÉ

CHEMICAL PHYSICS LETTERS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2022 vol. 794

0009-2614

Photo-induced isomerization between trans and cis isomers is the basis of azobenzene-based photoactive materials. In this work, isomerization and phase behavior of azobenzenes is studied theoretically, by means of a thermodynamically consistent kinetic expression for isomerization, in terms of activity and not concentration. This allows to reproduce the experimental observation that nematic ordering favours the trans isomer. Photoinduced phase transitions as a function of temperature and under irradiation are analyzed. Two regimes of nematic phase are found, for trans-saturated systems (high temperature), and cis-saturated systems (low temperature). For intermediate irradiation intensities there is a re-entrant isotropic phase between both nematic regimes