Kinetics of photochromic reactions of substituted azobenzenes in solutions, and in liquid crystalline and polymer matrices

Kinetics of photochromic reactions was studied in azobenzene derivatives: a zobenzene-containing crown ethers, and 4-methoxy-4'-halogen-substituted azo benzenes capable of forming liquid crystalline phases. The photoactive mate rials were dissolved in alkanes, and in polymer and liquid-crystalline matr ices. The isomerisation reactions follow the first order kinetics, in some polymer matrices, however, a dispersion of the rate constants was found. Th ermal cis-trans isomerisation rates of halogen-substituted azobenzenes in n -heptane were found practically independent of the substitutent. Kinetics o f the same reactions in liquid crystalline matrices seems to exhibit anomal ies near phase transitions of the matrices.